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1.
  • Abbey-Lee, Robin N., et al. (författare)
  • Effects of monoamine manipulations on the personality and gene expression of three-spined sticklebacks
  • 2019
  • Ingår i: Journal of Experimental Biology. - Cambridge : The Company of Biologists Ltd. - 0022-0949 .- 1477-9145. ; 222:20
  • Tidskriftsartikel (refereegranskat)abstract
    • Among-individual behavioral differences (i.e. animal personality) are commonly observed across taxa, although the underlying, causal mechanisms of such differences are poorly understood. Animal personality has been correlated with physiological functions as well as fitness-related traits. Variation in many aspects of monoamine systems, such as metabolite levels and gene polymorphisms, has been linked to behavioral variation. Therefore, here we experimentally investigated the potential role of monoamines in explaining individual variation in personality, using two common pharmaceuticals that respectively alter the levels of serotonin and dopamine in the brain: fluoxetine and ropinirole. We exposed three-spined sticklebacks, a species that shows animal personality, to either chemical alone or to a combination of the two chemicals, for 18 days. During the experiment, fish were assayed at four time points for the following personality traits: exploration, boldness, aggression and sociability. To quantify brain gene expression on short- and longer-term scales, fish were sampled at two time points. Our results show that monoamine manipulations influence fish behavior. Specifically, fish exposed to either fluoxetine or ropinirole were significantly bolder, and fish exposed to the two chemicals together tended to be bolder than control fish. Our monoamine manipulations did not alter the gene expression of monoamine or stress-associated neurotransmitter genes, but control, untreated fish showed covariation between gene expression and behavior. Specifically, exploration and boldness were predicted by genes in the dopaminergic, serotonergic and stress pathways, and sociability was predicted by genes in the dopaminergic and stress pathways. These results add further support to the links between monoaminergic systems and personality, and show that exposure to monoamines can causally alter animal personality.
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2.
  • Aldred, Nick, et al. (författare)
  • Confocal microscopy-based goniometry of barnacle cyprid permanent adhesive
  • 2013
  • Ingår i: Journal of Experimental Biology. - : Company of Biologists. - 0022-0949 .- 1477-9145. ; 216:11, s. 1969-1972
  • Tidskriftsartikel (refereegranskat)abstract
    • Biological adhesives are materials of particular interest in the fields of bio-inspired technology and antifouling research. The adhesive of adult barnacles has received much attention over the years; however, the permanent adhesive of the cyprid - the colonisation stage of barnacles - is a material about which very little is presently known. We applied confocal laser-scanning microscopy to the measurement of contact angles between the permanent adhesive of barnacle cyprid larvae and self-assembled monolayers of OH- and CH3-terminated thiols. Measurement of contact angles between actual bioadhesives and surfaces has never previously been achieved and the data may provide insight into the physicochemical properties and mechanism of action of these functional materials. The adhesive is a dual-phase system post-secretion, with the behaviour of the components governed separately by the surface chemistry. The findings imply that the cyprid permanent adhesion process is more complex than previously thought, necessitating broad re-evaluation of the system. Improved understanding will have significant implications for the production of barnacle-resistant coatings as well as development of bio-inspired glues for niche applications.
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3.
  • Almbro, Maria, et al. (författare)
  • Impaired escape flight ability in butterflies due to low flight muscle ratio prior to hibernation
  • 2008
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 211:1, s. 24-28
  • Tidskriftsartikel (refereegranskat)abstract
    • For an animal to escape an attacking predator, speed and manoeuvrability are likely to be crucial factors. Previous studies on reptiles and birds have revealed that gaining weight, due to for instance egg load or lipid accumulation, leads to impaired escape ability and possibly increases the risk of being caught by predators. Here we tested whether the flight performance of an insect, the small tortoiseshell butterfly (Aglais urticae), is affected by variations in body mass due to feeding by comparing flight performance parameters between individuals that (i) took flight spontaneously or after being subjected to a simulated predator attack and (ii) varied in flight muscle ratio (FMR: thorax mass/total body mass). The results show that butterflies that were subjected to a simulated predator attack flew at higher velocities and straighter than butterflies that were allowed to take off spontaneously. Furthermore, our study suggests, for the first time, that butterflies may experience impaired escape ability after feeding, which directly leads to a decrease in FMR; a reduction from 0.5 to 0.3 reduced escape flight velocity by about 37% at 0.5 m from the start. Finally, this study shows that FMR affects take-off angle and sinuosity, with steeper angles and more turning in butterflies with low FMR.
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4.
  • Altimiras, Jordi, 1967-, et al. (författare)
  • Intrinsic autoregulation of cardiac output in rainbow trout (Oncorhynchus mykiss) at different heart rates
  • 2004
  • Ingår i: J Exp Biol. - : The Company of Biologists. ; 207:Pt 2, s. 195-201
  • Tidskriftsartikel (refereegranskat)abstract
    • Intrinsic regulation of the heart in teleosts is partly driven by central venous pressure, which exerts a modulatory role on stroke volume according to the well-known Frank-Starling mechanism. Although this mechanism is well understood from heart perfusion studies, less is known about how this mechanism operates in vivo, where heart rate varies markedly. We used zatebradine, a bradycardic agent, to attain resting heart rates in surgically instrumented animals. A dose of zatebradine of 2.79+/-0.47 mg l(-1) decreased heart rate by half, from 44.4+/-4.19 beats min(-1) to 22.1+/-1.9 beats min(-1). Zatebradine had no significant effect on the peripheral vasculature and no inotropic effects, so was a suitable pharmacological agent with which to manipulate heart rate. When heart rate halved, cardiac output dropped to 87.5+/-4.6% of the control value, due to the concomitant increase in stroke volume to 165+/-13%. In vivo recordings of venous pressure at varying heart rates indicated that the partial compensation in cardiac output was possible through an increase in pressure in the sinus venosus, from -0.06+/-0.04 kPa at a control heart rate of 58.3+/-3.5 beats min(-1) (N=10) to 0.07+/-0.05 kPa after injection of zatebradine (4 mg kg(-1)). The operation of the so-called time-dependent autoregulatory mechanism was further demonstrated in perfused hearts. The positive pressures recorded in the sinus venosus at low heart rates coincident with non-invasive measurements in trout suggest that atrial filling in trout is more dependent on the build-up of pressure in the venous circulation (vis-a-tergo filling) than a suction mechanism during ventricular contraction (vis-a-fronte filling).
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5.
  • Anderson, Jennifer L, et al. (författare)
  • Thermal preference of Caenorhabditis elegans : a null model and empirical tests.
  • 2007
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 210:Pt 17
  • Tidskriftsartikel (refereegranskat)abstract
    • The preferred body temperature of ectotherms is typically inferred from the observed distribution of body temperatures in a laboratory thermal gradient. For very small organisms, however, that observed distribution might misrepresent true thermal preferences. Tiny ectotherms have limited thermal inertia, and so their body temperature and speed of movement will vary with their position along the gradient. In order to separate the direct effects of body temperature on movement from actual preference behaviour on a thermal gradient, we generate a null model (i.e. of non-thermoregulating individuals) of the spatial distribution of ectotherms on a thermal gradient and test the model using parameter values estimated from the movement of nematodes (Caenorhabditis elegans) at fixed temperatures and on a thermal gradient. We show that the standard lab strain N2, which is widely used in thermal gradient studies, avoids high temperature but otherwise does not exhibit a clear thermal preference, whereas the Hawaiian natural isolate CB4856 shows a clear preference for cool temperatures ( approximately 17 degrees C). These differences are not influenced substantially by changes in the starting position of worms in the gradient, the natal temperature of individuals or the presence and physiological state of bacterial food. These results demonstrate the value of an explicit null model of thermal effects and highlight problems in the standard model of C. elegans thermotaxis, showing the value of using natural isolates for tests of complex natural behaviours.
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6.
  • Andersson, Johan, et al. (författare)
  • Male sex pheromone release and female mate choice in a butterfly
  • 2007
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 210:6, s. 964-970
  • Tidskriftsartikel (refereegranskat)abstract
    • In butterflies female mate choice is influenced by both visual and olfactory cues, the latter of which are important at close range. Males of the green-veined butterfly, Pieris napi, are known to release citral ( mixture of geranial and neral, 1: 1), but its role(s) and conditions of release are not known. Here, we show that male P. napi release citral when interacting with conspecific males, conspecific females, heterospecific males and also when alone. The amount of citral released correlated strongly with male flight activity, which explained more than 70% of the variation. This suggests that males do not exercise control over turning release on or off, but rather that citral is emitted as a passive physical process during flight. Electroantennogram experiments showed that female antennal response was ten times more sensitive to citral than male response. Females expressed acceptance behavior when exposed to models made with freshly excised male wings or those treated with citral following chemical extraction, but not to ones with extracted wings only. Hence, these behavioral and electrophysiological tests provide strong evidence that citral is a signal from the male directed to the female during courtship, and that it functions as a male sex pheromone.
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7.
  • Andersson, Martin N., et al. (författare)
  • Diet and ambient temperature interact to shape plasma fatty acid composition, basal metabolic rate and oxidative stress in great tits
  • 2018
  • Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 221
  • Tidskriftsartikel (refereegranskat)abstract
    • Diet and ambient temperature affect animal physiology, survival and reproductive success. However, knowledge of how these environmental factors interact to shape physiological processes and life-history traits of birds and other animals is largely lacking. By exposing adult great tits (Parus major) to two contrasting diets (saturated or unsaturated fatty acids; SFAs and UFAs, respectively) and ambient temperatures (3°C versus 20°C) that the birds encounter in nature, we investigated the effects of these two factors on several physiological parameters. Our results show that diet and ambient temperature interact to affect the composition of plasma fatty acids, basal metabolic rate (BMR) and oxidative stress, which are thought to affect the life-history and survival of individuals. Specifically, birds provided the SFA-rich diet had higher mass-specific BMR and oxidative stress (levels of lipid peroxidation) after exposure to low compared with high ambient temperature, whereas the opposite pattern was evident for birds with a UFA-rich diet. Surprisingly, birds on the SFA diet had higher relative levels of monounsaturated fatty acids compared with the UFA-fed birds at low ambient temperature, whereas the opposite, and expected, pattern was found at the high temperature. Although the present study focuses on the physiological implications of the diet×temperature interaction, our results might also be important for the leading theories of ageing, which currently do not take interactions between environmental factors into account. In addition, the present results are important for wildlife management, especially with regards to anthropogenic feeding of wild animals across variable and changing climatic conditions.
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8.
  • Andersson, Martin, et al. (författare)
  • Peripheral modulation of pheromone response by inhibitory host compound in a beetle
  • 2010
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 213, s. 3332-3339
  • Tidskriftsartikel (refereegranskat)abstract
    • We identified several compounds, by gas chromatographic-electroantennographic detection (GC-EAD), that were antennally active in the bark beetle Ips typographus and also abundant in beetle-attacked spruce trees. One of them, 1,8-cineole (Ci), strongly inhibited the attraction to pheromone in the field. Single-sensillum recordings (SSRs) previously showed olfactory receptor neurons (ORNs) on I. typographus antennae selectively responding to Ci. All Ci neurons were found within sensilla co-inhabited by a pheromone neuron responding to cis-verbenol (cV); however, in other sensilla, the cV neuron was paired with a neuron not responding to any test odorant. We hypothesized that the colocalization of ORNs had a functional and ecological relevance. We show by SSR that Ci inhibited spontaneous activity of the cV neuron only in sensilla in which the Ci neuron was also present. Using mixtures of cV and Ci, we further show that responses to low doses (1-10 ng) of cV were significantly reduced when the colocalized Ci neuron simultaneously responded to high doses (1-10 mu g) of Ci. This indicated that the response of the Ci neuron, rather than ligand-receptor interactions in the cV neuron, caused the inhibition. Moreover, cV neurons paired with Ci neurons were more sensitive to cV alone than the ones paired with the non-responding ORN. Our observations question the traditional view that ORNs within a sensillum function as independent units. The colocalization of ORNs might sharpen adaptive responses to blends of semiochemicals with different ecological significance in the olfactory landscape.
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9.
  • Andreasson, Fredrik, et al. (författare)
  • Brood size constrains the development of endothermy in blue tits
  • 2016
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 219:14, s. 2212-2219
  • Tidskriftsartikel (refereegranskat)abstract
    • Altricial birds are unable to maintain body temperature when exposed to low ambient temperatures during the first days after hatching. Thermoregulatory capacity begins to form as postnatal development progresses, and eventually nestlings become homeothermic. Several factors may influence this development at both the level of the individual and the level of the whole brood, but to our knowledge no studies have focused on the effect of brood size per se on the development of endothermy in individual nestlings. We performed cooling experiments on blue tit (Cyanistes caeruleus) nestlings in the field, to study how different experimental brood sizes affected the development of endothermy in individual nestlings and the thermal environment experienced by the whole brood in the nest. Nestlings from all experimental brood sizes showed a decrease in cooling rate as they grew older, but birds from reduced broods showed an earlier onset of endothermy compared with nestlings from enlarged and control broods. This difference manifested during early development and gradually disappeared as nestlings grew older. The thermal environment in the nests differed between treatments during nestling development, such that nest temperature in reduced broods was lower than that in enlarged broods during all days and during nights at the end of the experimental period. We suggest that the development of endothermy in blue tit nestlings is not ontogenetically fixed, but instead may vary according to differences in developmental, nutritional and thermal conditions as determined by brood size.
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10.
  • Andreasson, Fredrik, et al. (författare)
  • Experimental facilitation of heat loss affects work rate and innate immune function in a breeding passerine bird
  • 2020
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 223:8
  • Tidskriftsartikel (refereegranskat)abstract
    • The capacity to get rid of excess heat produced during hard work is a possible constraint on parental effort during reproduction [heat dissipation limit (HDL) theory]. We released hard-working blue tits (Cyanistes caeruleus) from this constraint by experimentally removing ventral plumage. We then assessed whether this changed their reproductive effort (feeding rate and nestling size) and levels of self-maintenance (change in body mass and innate immune function). Feather-clipped females reduced the number of feeding visits and increased levels of constitutive innate immunity compared with unclipped females but did not fledge smaller nestlings. Thus, they increased self-maintenance without compromising current reproductive output. In contrast, feather clipping did not affect the number of feeding visits or innate immune function in males, despite increased heat loss rate. Our results show that analyses of physiological parameters, such as constitutive innate immune function, can be important when trying to understand sources of variation in investment in self-maintenance versus reproductive effort and that risk of overheating can influence innate immune function during reproduction.
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11.
  • Arroyo-Correa, Blanca, et al. (författare)
  • Bee and floral traits affect the characteristics of the vibrations experienced by flowers during buzz-pollination
  • 2019
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists Ltd. - 0022-0949 .- 1477-9145. ; 222:4
  • Tidskriftsartikel (refereegranskat)abstract
    • During buzz pollination, bees use their indirect flight muscles to produce vibrations that are transmitted to the flowers and result in pollen release. Although buzz pollination has been known for >100 years, we are still in the early stages of understanding how bee and floral characteristics affect the production and transmission of floral vibrations. Here, we analysed floral vibrations produced by four closely related bumblebee taxa (Bombus spp.) on two buzz-pollinated plants species (Solanum spp.). We measured floral vibrations transmitted to the flower to establish the extent to which the mechanical properties of floral vibrations depend on bee and plant characteristics. By comparing four bee taxa visiting the same plant species, we found that peak acceleration, root mean-squared acceleration (RMS) and frequency vary between bee taxa, but that neither bee size (intertegular distance) nor flower biomass (dry mass) affects peak acceleration, RMS or frequency. A comparison of floral vibrations of two bee taxa visiting flowers of two plant species showed that, while bee species affects peak acceleration, RMS and frequency, plant species only affects acceleration (peak acceleration and RMS), not frequency. When accounting for differences in the transmission of vibrations across the two types of flower, using a species-specific ‘coupling factor’, we found that RMS acceleration and peak displacement do not differ between plant species. This suggests that bees produce the same initial acceleration in different plants but that transmission of these vibrations through the flower is affected by floral characteristics.
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12.
  • Backström, Tobias, et al. (författare)
  • CRF and urotensin I effects on aggression and anxiety-like behavior in rainbow trout
  • 2011
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 214:6, s. 907-914
  • Tidskriftsartikel (refereegranskat)abstract
    • Corticotropin-releasing factor (CRF) is central in the stress response but also modulates several behaviors including anxiety-related behaviors and aggression. In this study, juvenile rainbow trout (Oncorhynchus mykiss) were tested for competitive ability, determined during dyadic fights for dominance, after intracerebroventricular (i.c.v.) administration of CRF, urotensin I (UI), the non-specific CRF antagonist alpha-helical RF9-41 (ahCRF) or the CRF receptor subtype 1-specific antagonist antalarmin, when paired with a mass-matched con-specific injected with saline. In addition, isolated fish received the same substances. Plasma cortisol and brain monoamines were monitored in all fish. Most fish receiving CRF showed a conspicuous behavior consisting of flaring the opercula, opening the mouth and violent shaking of the head from side to side. When this occurred, the fish immediately forfeited the fight. Similar behavior was observed in most fish receiving UI but no effect on outcome of dyadic fights was noted. This behavior seems similar to non-ambulatory motor activity seen in rats and could be anxiety related. Furthermore, fish receiving CRF at a dose of 1000. ng became subordinate, whereas all other treatments had no effects on the outcome of dyadic fights. In addition, isolated fish receiving ahCRF had lower brain stem concentrations of 5-hydroxyindoleacetic acid, serotonin, 3,4-dihydroxyphenylacetic acid and dopamine. In conclusion, CRF seems to attenuate competitive ability, and both CRF and UI seem to induce anxiety-like behavior.
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13.
  • Baird, Emily, et al. (författare)
  • Minimum viewing angle for visually guided ground speed control in bumblebees.
  • 2010
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 213:10, s. 1625-1632
  • Tidskriftsartikel (refereegranskat)abstract
    • To control flight, flying insects extract information from the pattern of visual motion generated during flight, known as optic flow. To regulate their ground speed, insects such as honeybees and Drosophila hold the rate of optic flow in the axial direction (front-to-back) constant. A consequence of this strategy is that its performance varies with the minimum viewing angle (the deviation from the frontal direction of the longitudinal axis of the insect) at which changes in axial optic flow are detected. The greater this angle, the later changes in the rate of optic flow, caused by changes in the density of the environment, will be detected. The aim of the present study is to examine the mechanisms of ground speed control in bumblebees and to identify the extent of the visual range over which optic flow for ground speed control is measured. Bumblebees were trained to fly through an experimental tunnel consisting of parallel vertical walls. Flights were recorded when (1) the distance between the tunnel walls was either 15 or 30 cm, (2) the visual texture on the tunnel walls provided either strong or weak optic flow cues and (3) the distance between the walls changed abruptly halfway along the tunnel's length. The results reveal that bumblebees regulate ground speed using optic flow cues and that changes in the rate of optic flow are detected at a minimum viewing angle of 23-30 deg., with a visual field that extends to approximately 155 deg. By measuring optic flow over a visual field that has a low minimum viewing angle, bumblebees are able to detect and respond to changes in the proximity of the environment well before they are encountered.
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14.
  • Balkenius, Anna, et al. (författare)
  • Behaviour towards an unpreferred colour: can green flowers attract foraging hawkmoths?
  • 2010
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 213, s. 3257-3262
  • Tidskriftsartikel (refereegranskat)abstract
    • Nave hawkmoths (Manduca sexta) learn from a single trial to approach and attempt to feed from an artificial flower of an innately unpreferred green colour even when a distractor flower with a preferred yellow colour is present. In some of the animals, the choice of the innately unpreferred colour during free-flight testing persists for several days despite not being rewarded and eventually leads to starvation. The results show that moths exhibit a very strong flower constancy that is not limited to the colours of nectar flowers.
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15.
  • Balkenius, Anna, et al. (författare)
  • Colour constancy in diurnal and nocturnal hawkmoths
  • 2004
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 207:19, s. 3307-3316
  • Tidskriftsartikel (refereegranskat)abstract
    • Diurnal and nocturnal hawkmoths have been shown to use colour vision for flower discrimination. Here, we present evidence that the nocturnal hawkmoth Deilephila elpenor and the diurnal hawkmoth Macroglossum stellatarum also have colour constancy. Colour constancy was shown in D. elpenor in two multiple-choice experiments with five different bluish colour patches under white and blue illumination and with five yellowish colour patches under white, blue and yellow illumination. The mechanism underlying colour constancy in both species was investigated in two dual-choice experiments. The choice behaviour is consistent with the use of the von Kries coefficient law. Although the moths have colour constancy, they react to the colour of the illumination. They make fewer choices when tested under the changed illumination, where they never receive a reward, compared with the training illumination. Even if colour constancy can be explained by a von Kries adaptation mechanism, the fact that the animals discriminate between different illuminations indicates that some additional process must be involved.
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16.
  • Balkenius, Anna (författare)
  • Flight behaviour of the hawkmoth Manduca sexta towards unimodal and multimodal targets
  • 2010
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 213, s. 3741-3747
  • Tidskriftsartikel (refereegranskat)abstract
    • Here, we analyse the flight behaviour of the hawkmoth Manduca sexta while it approaches three different artificial flower stimuli: a clearly visible blue flower, an invisible scented flower and a flower that is both visible and scented. By tracking the moths in fine temporal detail, we find that flight towards an artificial flower differs depending on whether the stimulus is unimodal (either visual or olfactory) or multimodal (both visual and olfactory). In all three cases, the moth reduces its speed as it nears the target but the speed is higher overall when the visual stimulus is not present. Visual feedback, as well as the concentration gradient of the odour, is used to guide the moths towards the stimulus. The main difference in flight behaviour between an approach towards a visual and a multimodal stimulus is that the olfactory information makes the moths turn more rapidly towards the multimodal stimulus. We also find that moths extend their proboscises in front of a clearly visible feeder independent of whether an odour is present. In contrast, a scented transparent artificial flower only occasionally triggers this response.
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17.
  • Balkenius, Anna, et al. (författare)
  • Interaction of visual and odour cues in the mushroom body of the hawkmoth Manduca sexta
  • 2009
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 212, s. 525-541
  • Tidskriftsartikel (refereegranskat)abstract
    • The responses to bimodal stimuli consisting of odour and colour were recorded using calcium-sensitive optical imaging in the mushroom bodies of the hawkmoth Manduca sexta. The results show that the activity in the mushroom bodies is influenced by both olfaction and vision. The interaction between the two modalities depends on the odour and the colour of the visual stimulus. A blue stimulus suppressed the response to a general flower scent(phenylacetaldehyde). By contrast, the response to a green leaf scent(1-octanol) was enhanced by the presence of the blue stimulus. A green colour had no influence on these odours but caused a marked increase in the response to an odour component (benzaldehyde) of the hawkmoth-pollinated Petunia axillaris.
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18.
  • Ballen, Cissy, et al. (författare)
  • Net superoxide levels: steeper increase with activity in cooler female and hotter male lizards
  • 2012
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 215:16, s. 731-735
  • Tidskriftsartikel (refereegranskat)abstract
    • Ectotherms increase their body temperature in response to ambient heat, thereby elevating their metabolic rate. An often inferred consequence of this is an overall upregulation of gene expression and energetic expenditure, and a concomitant increased production of reactive oxygen species (e.g. superoxide) and, perhaps, a shortened lifespan. However, recent work shows that this may be a superficial interpretation. For example, sometimes a reduced temperature may in fact trigger up-regulation of gene expression. We studied temperature and associated activity effects in male and female Australian painted dragon lizards (Ctenophorus pictus) by allowing the lizards to bask for 4 h versus 12 h, and scoring their associated activity (inactive versus active basking and foraging). As predicted, long-basking lizards (hereafter ‘hot’) showed heightened activity in both sexes, with a more pronounced effect in females. We then tested for sex-specific effects of basking treatment and activity levels on the increase in net levels of superoxide. In males, short-baskers (hereafter ‘cold’) had significantly more rapidly decreasing levels of superoxide per unit increasing activity than hot males. In females, however, superoxide levels increased faster with increasing activity in the cold than in the hot basking treatment, and females earlier in the ovarian cycle had lower superoxide levels than females closer to ovulation. In short, males and females differ in how their levels of reactive oxygen species change with temperature-triggered activity.
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19.
  • Barclay, C J, et al. (författare)
  • Initial mechanical efficiency of isolated cardiac muscle
  • 2003
  • Ingår i: Journal of Experimental Biology. - 0022-0949 .- 1477-9145. ; 206:Pt 16, s. 2725-32
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to determine whether the initial mechanical efficiency (ratio of work output to initial metabolic cost) of isolated cardiac muscle is over 60%, as has been reported previously, or whether it is approximately 30%, as suggested by an estimate based on the well-established net mechanical efficiency (ratio of work output to total, suprabasal energy cost) of 15%. Determination of initial efficiency required separation of the enthalpy output (i.e. heat + work) into initial and recovery components. The former corresponds to energy produced by reactions that use high-energy phosphates and the latter to energy produced in the regeneration of high-energy phosphates. The two components were separated mathematically. Experiments were performed in vitro (30 degrees C) using preparations dissected from rat left ventricular papillary muscles (N=13). Muscle work output and heat production were measured during a series of 40 contractions using a contraction protocol designed to mimic in vivo papillary muscle activity. Net mechanical efficiency was 13.3+/-0.7%. The total enthalpy output was 2.16 times greater than the initial enthalpy output, so that initial mechanical efficiency was 28.1+/-1.2%.
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20.
  • Beckmann, Holger, et al. (författare)
  • Spectral sensitivity in Onychophora (velvet worms) revealed by electroretinograms, phototactic behaviour and opsin gene expression.
  • 2015
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 218:6, s. 915-922
  • Tidskriftsartikel (refereegranskat)abstract
    • Onychophorans typically possess a pair of simple eyes, inherited from the last common ancestor of Panarthropoda (Onychophora + Tardigrada + Arthropoda). These visual organs are thought to be homologous to the arthropod median ocelli, whereas the compound eyes most likely evolved in the arthropod lineage. To gain insights into the ancestral function and evolution of the visual system in panarthropods, we investigated phototactic behaviour, opsin gene expression and the spectral sensitivity of the eyes in two representative species of Onychophora: Euperipatoides rowelli (Peripatopsidae), and Principapillatus hitoyensis (Peripatidae). Our behavioural analyses, in conjunction with previous data, demonstrate that both species exhibit photonegative responses to wavelengths ranging from ultraviolet to green light (370-530 nm), while electroretinograms reveal that the onychophoran eye is maximally sensitive to blue light (peak sensitivity ~480 nm). Template fits to the obtained sensitivities suggest that the onychophoran eye is monochromatic. To clarify on which type of opsin the single visual pigment is based, we localised the corresponding mRNA in the onychophoran eye and brain using in situ hybridization. Our data show that the r-opsin gene (onychopsin) is expressed exclusively in the photoreceptor cells of the eye, whereas the c-opsin mRNA is confined to optic ganglion cells and the brain. Together, our findings suggest that the onychopsin is involved in vision, whereas the c-opsin might have a photoreceptive, non-visual function in onychophorans.
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21.
  • Berry, Richard P., et al. (författare)
  • Ocellar adaptations for dim light vision in a nocturnal bee
  • 2011
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 214:8, s. 1283-1293
  • Tidskriftsartikel (refereegranskat)abstract
    • Growing evidence indicates that insect ocelli are strongly adapted to meet the specific functional requirements in the environment in which that insect lives. We investigated how the ocelli of the nocturnal bee Megalopta genalis are adapted to life in the dim understory of a tropical rainforest. Using a combination of light microscopy and three-dimensional reconstruction, we found that the retinae contain bar-shaped rhabdoms loosely arranged in a radial pattern around multi-layered lenses, and that both lenses and retinae form complex non-spherical shapes reminiscent of those described in other ocelli. Intracellular electrophysiology revealed that the photoreceptors have high absolute sensitivity, but that the threshold location varied widely between 109 and 10(11) photons cm(-2) s(-1). Higher sensitivity and greater visual reliability may be obtained at the expense of temporal resolution: the corner frequencies of dark-adapted ocellar photoreceptors were just 4-11 Hz. Spectral sensitivity profiles consistently peaked at 500 nm. Unlike the ocelli of other flying insects, we did not detect UV-sensitive visual pigments in M. genalis, which may be attributable to a scarcity of UV photons under the rainforest canopy at night. In contrast to earlier predictions based on anatomy, the photoreceptors are not sensitive to the e-vector of polarised light. Megalopta genalis ocellar photoreceptors possess a number of unusual properties, including inherently high response variability and the ability to produce spike-like potentials. These properties bear similarities to photoreceptors in the compound eye of the cockroach, and we suggest that the two insects share physiological characteristics optimised for vision in dim light.
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22.
  • Bianco, Giuseppe, et al. (författare)
  • Magnetic body alignment in migratory songbirds : a computer vision approach
  • 2019
  • Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 222
  • Tidskriftsartikel (refereegranskat)abstract
    • Several invertebrate and vertebrate species have been shown to align their body relative to the geomagnetic field. Many hypotheses have been proposed to explain the adaptive significance of magnetic body alignment outside the context of navigation. However, experimental evidence to investigate alternative hypotheses is still limited. We present a new setup to track the preferential body alignment relative to the geomagnetic field in captive animals using computer vision. We tested our method on three species of migratory songbirds and provide evidence that they align their body with the geomagnetic field. We suggest that this behaviour is involved in the underlying mechanism for compass orientation and calibration, which may occur near to sunrise and sunset periods. Our method could easily be extended to other species and used to test a large set of hypotheses to explain the mechanisms behind the magnetic body alignment and the magnetic sense in general.
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23.
  • Bijma, Nienke N., et al. (författare)
  • The effect of surface topography on the ball-rolling ability of Kheper lamarcki (Scarabaeidae)
  • 2024
  • Ingår i: The Journal of experimental biology. - 1477-9145 .- 0022-0949. ; 227:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The most effective way to avoid intense inter- and intra-specific competition at the dung source, and to increase the distance to the other competitors, is to follow a single straight bearing. While ball-rolling dung beetles manage to roll their dung balls along nearly perfect straight paths when traversing flat terrain, the paths that they take when traversing more complex (natural) terrain are not well understood. In this study, we investigate the effect of complex surface topographies on the ball-rolling ability of Kheper lamarcki. Our results reveal that ball-rolling trajectories are strongly influenced by the characteristic scale of the surface structure. Surfaces with an increasing similarity between the average distance of elevations and the ball radius cause progressively more difficulties during ball transportation. The most important factor causing difficulties in ball transportation appears to be the slope of the substrate. Our results show that, on surfaces with a slope of 7.5 deg, more than 60% of the dung beetles lose control of their ball. Although dung beetles still successfully roll their dung ball against the slope on such inclinations, their ability to roll the dung ball sideways diminishes. However, dung beetles do not seem to adapt their path on inclines such that they roll their ball in the direction against the slope. We conclude that dung beetles strive for a straight trajectory away from the dung pile, and that their actual path is the result of adaptations to particular surface topographies.
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24.
  • Birgersson, Göran, et al. (författare)
  • Smelling your way to food: can bed bugs use our odour?
  • 2012
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 215, s. 623-629
  • Tidskriftsartikel (refereegranskat)abstract
    • The resurgence in developed countries of the common bed bug, Cimex lectularius, has led to a search for new sustainable methods to monitor and control this human ectoparasite. Because of increased resistance to insecticides, traps baited with attractive cues are considered a promising method to be developed into efficient monitoring tools for bed bugs. Despite their potential as attractants, only a few studies have investigated the odorant cues implicated in the attraction of bed bugs to human hosts. In this study, we used aeration extracts from human volunteers to assess the role of olfaction in host searching by bed bugs. By coupled gas chromatography and single sensillum recordings on all the antennal sensilla, we measured the electrophysiological response elicited by the compounds present in our human odour extracts. Only five compounds were clearly detected by the olfactory receptor neurons housed in the smooth-peg sensilla of the bed bugs. We tested the behavioural effect of these extracts in a still-air arena and showed a gradient of repellence linked to the dose, as well as a higher propensity of local search behaviour associated with human odours containing a lower ratio of 6-methyl-5-hepten-2-one to C7–C10 aldehydes. We conclude that human odour alone has a weak influence on the behaviour of C. lectularius and we propose that human kairomones may have a significant impact on bed bug behaviour in combination with heat and carbon dioxide, the only two currently known attractive vertebrate cues used by bed bugs for host seeking.
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25.
  • Birse, Ryan T., et al. (författare)
  • Regulation of insulin-producing cells in the adult Drosophila brain via the tachykinin peptide receptor DTKR
  • 2011
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 214, s. 4201-4208
  • Tidskriftsartikel (refereegranskat)abstract
    • Drosophila insulin-like peptides (DILPs) play important hormonal roles in the regulation of metabolic carbohydrates and lipids, but also in reproduction, growth, stress resistance and aging. In spite of intense studies of insulin signaling in Drosophilag the regulation of DILP production and release in adult fruit flies is poorly understood. Here we investigated the role of Drosophila tachykinin-related peptides (DTKs) and their receptors, DTKR and NKD, in the regulation of brain insulin-producing cells (IPCs) and aspects of DILP signaling. First, we show DTK-immunoreactive axon terminations close to the presumed dendrites of the IPCs, and DTKR immunolabeling in these cells. Second, we utilized targeted RNA interference to knock down expression of the DTK receptor, DTKR, in IPCs and monitored the effects on Dilp transcript levels in the brains of fed and starved flies. Dilp2 and Dilp3, but not Dilp5, transcripts were significantly affected by DTKR knockdown in IPCs, both in fed and starved flies. Both Dilp2 and Dilp3 transcripts increased in fed flies with DTKR diminished in IPCs whereas at starvation the Dilp3 transcript plummeted and Dilp2 increased. We also measured trehalose and lipid levels as well as survival in transgene flies at starvation. Knockdown of DTKR in IPCs leads to increased lifespan and a faster decrease of trehalose at starvation but has no significant effect on lipid levels. Finally, we targeted the IPCs with RNAi or ectopic expression of the other DTK receptor, NKD, but found no effect on survival at starvation. Our results suggest that DTK signaling, via DTKR, regulates the brain IPCs.
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26.
  • Bisch-Knaden, Sonja, et al. (författare)
  • Olfactory coding in five moth species from two families
  • 2012
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 215:9, s. 1542-1551
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the present study was to determine what impact phylogeny and life history might have on the coding of odours in the brain. Using three species of hawk moths (Sphingidae) and two species of owlet moths (Noctuidae), we visualized neural activity patterns in the antennal lobe, the first olfactory neuropil in insects, evoked by a set of ecologically relevant plant volatiles. Our results suggest that even between the two phylogenetically distant moth families, basic olfactory coding features are similar. But we also found different coding strategies in the moths' antennal lobe; namely, more specific patterns for chemically similar odorants in the two noctuid species than in the three sphingid species tested. This difference demonstrates the impact of the phylogenetic distance between species from different families despite some parallel life history traits found in both families. Furthermore, pronounced differences in larval and adult diet among the sphingids did not translate into differences in the olfactory code; instead, the three species had almost identical coding patterns.
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27.
  • Blary, Constance L.M., et al. (författare)
  • Low achromatic contrast sensitivity in birds : a common attribute shared by many phylogenetic orders
  • 2024
  • Ingår i: The Journal of experimental biology. - 1477-9145. ; 227:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Vision is an important sensory modality in birds, which can outperform other vertebrates in some visual abilities. However, sensitivity to achromatic contrasts - the ability to discern luminance difference between two objects or an object and its background - has been shown to be lower in birds compared with other vertebrates. We conducted a comparative study to evaluate the achromatic contrast sensitivity of 32 bird species from 12 orders using the optocollic reflex technique. We then performed an analysis to test for potential variability in contrast sensitivity depending on the corneal diameter to the axial length ratio, a proxy of the retinal image brightness. To account for potential influences of evolutionary relatedness, we included phylogeny in our analyses. We found a low achromatic contrast sensitivity for all avian species studied compared with other vertebrates (except small mammals), with high variability between species. This variability is partly related to phylogeny but appears to be independent of image brightness.
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28.
  • Bok, Michael J, et al. (författare)
  • Photoresponses in the radiolar eyes of the fan worm Acromegalomma vesiculosum
  • 2019
  • Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 222:23
  • Tidskriftsartikel (refereegranskat)abstract
    • Fan worms (Annelida: Sabellidae) possess compound eyes and other photoreceptors on their radiolar feeding tentacles. These eyes putatively serve as an alarm system that alerts the worm to encroaching threats, eliciting a rapid defensive retraction into their protective tube. The structure and independent evolutionary derivation of these radiolar eyes make them a fascinating target for exploring the emergence of new sensory systems and visually guided behaviours. However, little is known about their physiology and how this impacts their function. Here, we present electroretinogram recordings from the radiolar eyes of the fan worm Acromegalomma vesiculosum We examine their spectral sensitivity along with their dynamic range and temporal resolution. Our results show that they possess one class of photoreceptors with a single visual pigment peaking in the blue-green part of the spectrum around 510 nm, which matches the dominant wavelengths in their shallow coastal habitats. We found the eyes to have a rather high temporal resolution with a critical flicker fusion frequency around 35 Hz. The high temporal resolution of this response is ideally suited for detecting rapidly moving predators but also necessitates downstream signal processing to filter out caustic wave flicker. This study provides a fundamental understanding of how these eyes function. Furthermore, these findings emphasise a set of dynamic physiological principles that are well suited for governing a multi-eyed startle response in coastal aquatic habitats.
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29.
  • Bonaventure Omondi, Aman, et al. (författare)
  • Functional development of carbon dioxide detection in the maxillary palp of Anopheles gambiae
  • 2015
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 218, s. 2482-2488
  • Tidskriftsartikel (refereegranskat)abstract
    • Olfactory information drives several behaviours critical for the survival and persistence of insect pests and vectors. Insect behaviour is variable, linked to their biological needs, and regulated by physiological dynamics. For mosquitoes, CO2 is an important cue that signifies the presence of a host, and which elicits activation and attraction. To investigate the genetic basis of olfactory modulation in mosquitoes, we assayed changes in CO2 detection from receptor gene expression through physiological function to behaviour, associated with the onset of host seeking in the malaria vector, Anopheles gambiae. The gene encoding a subunit of the CO2 receptor, AgGr22, was found to be significantly up-regulated in host-seeking females, consistent with a significant increase in sensitivity of CO2-responsive neurons (cpA) housed in capitate peg sensilla of the maxillary palp. In addition, the odorant receptor AgOr28, which is expressed in cpC neurons, was significantly up-regulated. In contrast, AgOr8, which is expressed in cpB neurons, was not affected by this change in physiological state, in agreement with results for the obligate co-receptor Orco. Moreover, the sensitivity of the cpB neuron to (R)-1-octen-3-ol, a well-known mammalian kairomone, did not change in response to the onset of host seeking. The concentration of CO2 flux influenced both the propensity of A. gambiae to take off into the wind and the speed with which this activation occurred. Female A. gambiae mosquitoes responded to CO2 whether mature for host seeking or not, but onset of host seeking enhanced sensitivity and speed of activation at relevant doses of CO2.
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30.
  • Boussard, Annika, et al. (författare)
  • Brain size does not predict learning strategies in a serial reversal learning test
  • 2020
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 223:15
  • Tidskriftsartikel (refereegranskat)abstract
    • Reversal learning assays are commonly used across a wide range of taxa to investigate associative learning and behavioural flexibility. In serial reversal learning, the reward contingency in a binary discrimination is reversed multiple times. Performance during serial reversal learning varies greatly at the interspecific level, as some animals adopt a rule-based strategy that enables them to switch quickly between reward contingencies. A larger relative brain size, generating enhanced learning ability and increased behavioural flexibility, has been proposed to be an important factor underlying this variation. Here, we experimentally tested this hypothesis at the intraspecific level. We used guppies (Poecilia reticulata) artificially selected for small and large relative brain size, with matching differences in neuron number, in a serial reversal learning assay. We tested 96 individuals over 10 serial reversals and found that learning performance and memory were predicted by brain size, whereas differences in efficient learning strategies were not. We conclude that variation in brain size and neuron number is important for variation in learning performance and memory, but these differences are not great enough to cause the larger differences in efficient learning strategies observed at higher taxonomic levels.
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31.
  • Bradacs, H, et al. (författare)
  • Differential physiology and morphology of phasic and tonic motor axons in a crayfish limb extensor muscle
  • 1997
  • Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 200:4Pt 4, s. 677-691
  • Tidskriftsartikel (refereegranskat)abstract
    • The main leg extensor muscle of the crayfish Procambarus clarkii is innervated by two excitatory motor axons (phasic and tonic) and by the common inhibitory axon. The axons and their terminals were investigated using vital fluorescent dyes, antibodies and electron microscopy. Correlative physiological observations were made using intracellular microelectrodes and focal ‘macro-patch’ electrodes. The excitatory axons innervate the muscle fibres more extensively than does the inhibitory axon. Striking morphological and physiological differences between the two excitatory axons were discerned. The tonic motor axon contains many mitochondria and has varicose junctional terminals; the phasic axon has fewer mitochondria and thin terminals. In freely moving animals, the tonic axon is very active, whereas the phasic axon is inactive but fires in brief bursts during walking. Throughout the muscle, tonic excitatory postsynaptic potentials (EPSPs) are very small at low frequencies and facilitate greatly at higher frequencies. The EPSPs of the phasic axon are larger at low frequencies and depress with maintained stimulation. At identified tonic terminals, quantal content at 1–10 Hz is very low, whereas at identified phasic terminals, quantal content is 50-to 200-fold greater. The results indicate that transmitter release is regulated differently at the synapses of the two axons.
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32.
  • Braga Gonçalves, Inês, et al. (författare)
  • Embryo oxygenation in pipefish brood pouches: novel insights
  • 2015
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 218:11, s. 1639-1646
  • Tidskriftsartikel (refereegranskat)abstract
    • The pipefish brood pouch presents a unique mode of parental care that enables males to protect, osmoregulate, nourish and oxygenate the developing young. Using a very fine O-2 probe, we assessed the extent to which males of the broad-nosed pipefish (Syngnathus typhle) oxygenate the developing embryos and are able to maintain pouch fluid O-2 levels when brooding in normoxia (100% O-2 saturation) and hypoxia (40% O-2 saturation) for 24 days. In both treatments, pouch fluid-O-2 saturation levels were lower compared with the surrounding water and decreased throughout the brooding period, reflecting greater offspring demand for O-2 during development and/or decreasing paternal ability to provide O-2 to the embryos. Male condition (hepatosomatic index) was negatively affected by hypoxia. Larger males had higher pouch fluid O-2 saturation levels compared with smaller males, and levels were higher in the bottom section of the pouch compared with other sections. Embryo size was positively correlated with O-2 availability, irrespective of their position in the pouch. Two important conclusions can be drawn from our findings. First, our results highlight a potential limitation to brooding within the pouch and dismiss the notion of closed brood pouches as well-oxygenated structures promoting the evolution of larger eggs in syngnathids. Second, we provide direct evidence that paternal care improves with male size in this species. This finding offers an explanation for the documented strong female preference for larger partners because, in terms of oxygenation, the brood pouch can restrict embryo growth.
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33.
  • Brandt, Christian, et al. (författare)
  • Development of vocalization and hearing in American mink (Neovison vison).
  • 2013
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 216:Pt 18, s. 3542-50
  • Tidskriftsartikel (refereegranskat)abstract
    • American mink (Neovison vison) kits are born altricial and fully dependent on maternal care, for which the kits' vocalizations appear essential. We used auditory brainstem responses (ABRs) to determine: (1) hearing sensitivity of adult females from two breeding lines known to differ in maternal behaviour and (2) development of hearing in kits 8-52 days of age. We also studied sound production in 20 kits throughout postnatal days 1 to 44. Adult female mink had a broad hearing range from 1 kHz to above 70 kHz, with peak sensitivity (threshold of 20 dB SPL) at 8-10 kHz, and no difference in sensitivity between the two breeding lines (P>0.22) to explain the difference in maternal care. Mink kits showed no signs of hearing up to postnatal day 24. From day 30, all kits had ABRs indicative of hearing. Hearing sensitivity increased with age, but was still below the adult level at postnatal day 52. When separated from their mothers, kits vocalized loudly. Until the age of 22 days, 90% of all kits vocalized with no significant decline with age (P=0.27). From day 25, concurrent with the start of hearing, the number of vocalizing kits decreased with age (P<0.001), in particular in kits that were re-tested (P=0.004). Large numbers of mink are kept in fur industry farms, and our results are important to the understanding of sound communication, which is part of their natural behaviour. Our results also suggest mink as an interesting model for studying the development of mammalian hearing and its correlation to sound production.
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34.
  • Brijs, Jeroen, et al. (författare)
  • Effects of feeding on in vivo motility patterns in the proximal intestine of shorthorn sculpin (Myoxocephalus scorpius)
  • 2014
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 217:17, s. 3015-3027
  • Tidskriftsartikel (refereegranskat)abstract
    • This is the first study to catalogue the diverse array of in vivo motility patterns in a teleost fish and how they are affected by feeding. Video recordings of exteriorised proximal intestine from fasted and fed shorthorn sculpin (Myoxocephalus scorpius) were used to generate spatio-temporal maps to portray and quantify motility patterns. Propagating and non-propagating contractions were observed to occur at different frequencies and durations. The most apparent difference between the feeding states was that bands of relatively high amplitude contractions propagating slowly in the anal direction were observed in all fasted fish (N=10) but in only 35% of fed fish (N=11). Additionally, fed fish displayed a reduced frequency (0.21 +/- 0.03 versus 0.32 +/- 0.06 contractions min(-1)) and rhythmicity of these contractions compared with fasted fish. Although the underlying mechanisms of these slow anally propagating contractions differ from those of mammalian migrating motor complexes, we believe that they may play a similar role in shorthorn sculpin during the interdigestive period, to potentially remove food remnants and prevent the establishment of pathogens. 'Ripples' were the most prevalent contraction type in shorthorn sculpin and may be important during mixing and absorption. The persistence of shallow ripples and pendular movements of longitudinal muscle after tetrodotoxin (1 mu mol l(-1)) treatment suggests these contractions were myogenic in origin. The present study highlights both similarities and differences in motility patterns between shorthorn sculpin and other vertebrates, as well as providing a platform to examine other aspects of gastrointestinal functions in fish, including the impact of environmental changes.
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35.
  • Brijs, Jeroen, et al. (författare)
  • Experimental manipulations of tissue oxygen supply do not affect warming tolerance of European perch
  • 2015
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 218, s. 2448-2454
  • Tidskriftsartikel (refereegranskat)abstract
    • A progressive inability of the cardiorespiratory system to maintain systemic oxygen supply at elevated temperatures has been suggested to reduce aerobic scope and the upper thermal limit of aquatic ectotherms. However, few studies have directly investigated the dependence of thermal limits on oxygen transport capacity. By manipulating oxygen availability (via environmental hyperoxia) and blood oxygen carrying capacity (via experimentally-induced anemia) in European perch (Perca fluviatilis, Linneaus), we investigated the effects of oxygen transport capacity on aerobic scope and the critical thermal maximum (CTmax). Hyperoxia resulted in a two-fold increase in aerobic scope at the control temperature of 23°C, but this did not translate to an elevated CTmax in comparison with control fish (34.6±0.1°C vs. 34.0±0.5°C, respectively). Anemia (∼43% reduction in haemoglobin concentration) did not cause a reduction in aerobic scope nor CTmax (33.8±0.3°C) compared with control fish. Additionally, oxygen consumption rates of anemic perch during thermal ramping increased in a similar exponential manner as in control fish, highlighting that perch have an impressive capacity to compensate for a substantial reduction in blood oxygen carrying capacity. Taken together, these results indicate that oxygen limitation is not a universal mechanism determining the CTmax of fishes.
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36.
  • Brijs, Jeroen, et al. (författare)
  • Exposure to seawater increases intestinal motility in euryhaline rainbow trout (Oncorhynchus mykiss).
  • 2017
  • Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 220, s. 2397-2408
  • Tidskriftsartikel (refereegranskat)abstract
    • Upon exposure to seawater, euryhaline teleosts need to imbibe and desalinate seawater to allow for intestinal ion and water absorption, as this is essential for maintaining osmotic homeostasis. Despite the potential benefits of increased mixing and transport of imbibed water for increasing the efficiency of absorptive processes, the effect of water salinity on intestinal motility in teleosts remains unexplored. By qualitatively and quantitatively describing in vivo intestinal motility of euryhaline rainbow trout (Oncorhynchus mykiss), this study demonstrates that in freshwater, the most common motility pattern consisted of clusters of rhythmic, posteriorly propagating contractions that lasted ∼1-2 minutes followed by a period of quiescence lasting ∼4-5 minutes. This pattern closely resembles mammalian migrating motor complexes (MMCs). Following a transition to seawater, imbibed seawater resulted in a significant distension of the intestine and the frequency of MMCs increased two to three-fold with a concomitant reduction in the periods of quiescence. The increased frequency of MMCs was also accompanied by ripple-type contractions occuring every 12 to 60 seconds. These findings demonstrate that intestinal contractile activity of euryhaline teleosts is dramatically increased upon exposure to seawater, which is likely part of the overall response for maintaining osmotic homeostasis as increased drinking and mechanical perturbation of fluids is necessary to optimize intestinal ion and water absorption. Finally, the temporal response of intestinal motility in rainbow trout transitioning from freshwater to seawater coincides with previously documented physiological modifications associated with osmoregulation and may provide further insight on the underlying reasons shaping the migration patterns of salmonids.
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37.
  • Brijs, Jeroen, et al. (författare)
  • Extreme blood-boosting capacity of an Antarctic fish represents an adaptation to life in a sub-zero environment
  • 2020
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 223:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Blood doping, the practice of boosting the oxygen carrying capacity of blood, is an illegal strategy used by human athletes to enhance aerobic capacity and athletic performance. Interestingly, the practice of boosting blood oxygen carrying capacity is also naturally prevalent in the animal kingdom via the splenic release of stored erythrocytes. Here, we demonstrate that an Antarctic notothenioid fish, the bald notothen (Pagothenia borchgrevinki), is a master of this practice. Because of the sub-zero environment these fish inhabit, they sequester a large proportion of erythrocytes in the spleen during times of inactivity to reduce the energetic and physiological costs associated with continuously pumping highly viscous blood around the body. However, in response to metabolically demanding situations (i.e. exercise and feeding), these fish contract the spleen to eject stored erythrocytes into circulation, which boosts blood oxygen carrying capacity by up to 207% (cf. exercise-induced increases of ∼40-60% in a range of other vertebrates and ∼5-25% in blood-doping athletes). By evaluating cardiorespiratory differences between splenectomized (unable to release erythrocytes from the spleen) and sham-operated individuals, we demonstrate the metabolic benefits (i.e. aerobic scope increase of 103%) and the cardiovascular trade-offs (i.e. ventral aortic blood pressure and cardiac workload increase of 12% and 30%, respectively) associated with the splenic blood-boosting strategy. In conclusion, this strategy provides bald notothens with an extraordinary facultative aerobic scope that enables an active lifestyle in the extreme Antarctic marine environment, while minimizing the energetic and physiological costs of transporting highly viscous blood during times of reduced energetic demand.
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38.
  • Brijs, J., et al. (författare)
  • In vivo aerobic metabolism of the rainbow trout gut and the effects of an acute temperature increase and stress event
  • 2018
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 221:14
  • Tidskriftsartikel (refereegranskat)abstract
    • The fish gut is responsible for numerous potentially energetically costly processes, yet little is known about its metabolism. Here, we provide the first in vivo measurements of aerobic metabolism of the gut in a teleost fish by measuring gut blood flow, as well as arterial and portal venous oxygen content. At 10 degrees C, gut oxygen uptake rate was 4.3 +/- 0.5 ml O-2 h(-1) kg(-1) (similar to 11 % of whole-animal oxygen uptake). Following acute warming to 15 degrees C, gut blood flow increased similar to 3.4-fold and gut oxygen uptake rate increased similar to 3.7-fold (16.0 +/- 3.3 ml O-2 h(-1) kg(-1)), now representing similar to 25% of whole-animal oxygen uptake. Although gut blood flow decreased following an acute stress event at 15 degrees C, gut oxygen uptake remained unchanged as a result of a similar to 2-fold increase in oxygen extraction. The high metabolic thermal sensitivity of the gut could have important implications for the overall aerobic capacity and performance of fish in a warming world and warrants further investigation.
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39.
  •  
40.
  • Brijs, Jeroen, et al. (författare)
  • The presence and role of interstitial cells of Cajal in the proximal intestine of shorthorn sculpin (Myoxocephalus scorpius)
  • 2017
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 220, s. 347-357
  • Tidskriftsartikel (refereegranskat)abstract
    • Rhythmic contractions of the mammalian gastrointestinal tract can occur in the absence of neuronal or hormonal stimulation due to the generation of spontaneous electrical activity by interstitial cells of Cajal (ICC) that are electrically coupled to smooth muscle cells. The myogenically-driven component of gastrointestinal motility patterns in fish likely also involves ICC, however, little is known of their presence, distribution and function in any fish species. In the present study, we combined immunohistochemistry and in vivo recordings of intestinal motility to investigate the involvement of ICC in the motility of the proximal intestine in adult shorthorn sculpin (Myoxocephalus scorpius). Antibodies against anoctamin 1 (Ano1, a Ca2+-activated Cl- channel), revealed a dense network of multipolar, repeatedly branching cells in the myenteric region of the proximal intestine, similar in many regards to the mammalian ICC-MY network. The addition of benzbromarone, a potent blocker of Ano1, altered the motility patterns seen in vivo after neural blockade with TTX. The results indicate that ICC are integral for the generation and propagation of the majority of rhythmic contractile patterns in fish, although their frequency and amplitude can be modulated via neural activity.
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41.
  • Broggi, Juli, et al. (författare)
  • Individual response in body mass and basal metabolism to the risks of predation and starvation in passerines
  • 2023
  • Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 226:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Wintering energy management in small passerines has focused on the adaptive regulation of the daily acquisition of energy reserves within a starvation-predation trade-off framework. However, the possibility that the energetic cost of living, i.e. basal metabolic rate (BMR), is being modulated as part of the management energy strategy has been largely neglected. Here, we addressed this possibility by experimentally exposing captive great tits (Parus major) during winter to two consecutive treatments of increased starvation and predation risk for each individual bird. Body mass and BMR were measured prior to and after each week-long treatment. We predicted that birds should be lighter but with a higher metabolic capacity (higher BMR) as a response to increased predation risk, and that birds should increase internal reserves while reducing their cost of living (lower BMR) when exposed to increased starvation risk. Wintering great tits kept a constant body mass independently of a week-long predation or starvation treatment. However, great tits reduced the cost of living (lower BMR) when exposed to the starvation treatment, while BMR remained unaffected by the predation treatment. Energy management in wintering small birds partly relies on BMR regulation, which challenges the current theoretical framework based on body mass regulation.
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42.
  • Buechel, Séverine D., et al. (författare)
  • Variation in sexual brain size dimorphism over the breeding cycle in the three-spined stickleback
  • 2019
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 222:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Snapshot analyses have demonstrated dramatic intraspecific variation in the degree of brain sexual size dimorphism (SSD). Although brain SSDis believed to be generated by the sex-specific cognitive demands of reproduction, the relative roles of developmental and population-specific contributions to variation in brain SSD remain little studied. Using a common garden experiment, we tested for sex-specific changes in brain anatomy over the breeding cycle in three-spined stickleback (Gasterosteus aculeatus) sampled from four locations in northern Europe. We found that the male brain increased in size (ca. 24%) significantly more than the female brain towards breeding, and that the resulting brain SSD was similar (ca. 20%) for all populations over the breeding cycle. Our findings support the notion that the stickleback brain is highly plastic and changes over the breeding cycle, especially in males, likely as an adaptive response to the cognitive demands of reproduction (e.g. nest construction and parental care). The results also provide evidence to suggest that breeding-related changes in brain size may be the reason for the widely varying estimates of brain SSD across studies of this species, cautioning against interpreting brain size measurements from a single time point as fixed/static.
  •  
43.
  • Bäckman, Johan, et al. (författare)
  • Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus.
  • 2002
  • Ingår i: Journal of Experimental Biology. - 1477-9145. ; 205:Pt 7, s. 905-910
  • Tidskriftsartikel (refereegranskat)abstract
    • Swifts regularly spend the night flying at high altitude. From previous studies based on tracking radar observations, we know that they stay airborne during the night and prefer to orient themselves into the wind direction with an increased angular concentration with increasing wind speed. In this study, we investigated the orientation relative to the wind of individual swifts by frequency (discrete Fourier transform) and autocorrelation analysis based on time series (10s intervals) of the angle between the swifts' heading and the wind direction for radar trackings of long duration (9-60 min). The swifts often showed a significant harmonic oscillation of their heading direction relative to the wind, with a frequency mostly in the range 1-17 mHz, corresponding to cycle periods of 1-16 min. The swifts also sometimes performed circling flights at low wind speeds. Wind speed ranged from 1.3 to 14.8 m s(-1), and we expected to find different patterns of orientation at different wind speeds, assuming that the swifts adapt their orientation to avoid substantial displacement during their nocturnal flights. However, oscillatory orientation was found at all wind speeds with variable frequencies/periods that did not show any consistent relationship with wind speed. It remains to be shown whether cyclic heading changes are a regular feature of bird orientation.
  •  
44.
  • Cannon, Barbara, et al. (författare)
  • Nonshivering thermogenesis and its adequate measurement in metabolic studies
  • 2011
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 214:Pt 2, s. 242-53
  • Tidskriftsartikel (refereegranskat)abstract
    • Alterations in nonshivering thermogenesis are presently discussed as being both potentially causative of and able to counteract obesity. However, the necessity for mammals to defend their body temperature means that the ambient temperature profoundly affects the outcome and interpretation of metabolic experiments. An adequate understanding and assessment of nonshivering thermogenesis is therefore paramount for metabolic studies. Classical nonshivering thermogenesis is facultative, i.e. it is only activated when an animal acutely requires extra heat (switched on in minutes), and adaptive, i.e. it takes weeks for an increase in capacity to develop. Nonshivering thermogenesis is fully due to brown adipose tissue activity; adaptation corresponds to the recruitment of this tissue. Diet-induced thermogenesis is probably also facultative and adaptive and due to brown adipose tissue activity. Although all mammals respond to injected/infused norepinephrine (noradrenaline) with an increase in metabolism, in non-adapted mammals this increase mainly represents the response of organs not involved in nonshivering thermogenesis; only the increase after adaptation represents nonshivering thermogenesis. Thermogenesis (metabolism) should be expressed per animal, and not per body mass [not even to any power (0.75 or 0.66)]. A 'cold tolerance test' does not examine nonshivering thermogenesis capacity; rather it tests shivering capacity and endurance. For mice, normal animal house temperatures are markedly below thermoneutrality, and the mice therefore have a metabolic rate and food consumption about 1.5 times higher than their intrinsic requirements. Housing and examining mice at normal house temperatures carries a high risk of identifying false positives for intrinsic metabolic changes; in particular, mutations/treatments that affect the animal's insulation (fur, skin) may lead to such problems. Correspondingly, true alterations in intrinsic metabolic rate remain undetected when metabolism is examined at temperatures below thermoneutrality. Thus, experiments with animals kept and examined at thermoneutrality are likely to yield an improved possibility of identifying agents and genes important for human energy balance.
  •  
45.
  • Céchetto, Clément, et al. (författare)
  • Visual detection threshold in the echolocating Daubenton’s bat (Myotis daubentonii)
  • 2023
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 226:2
  • Tidskriftsartikel (refereegranskat)abstract
    • All bats possess eyes that are of adaptive value. Echolocating bats have retinae dominated by rod photoreceptors and use dim light vision for navigation, and in rare cases for hunting. However, the visual detection threshold of insectivorous echolocating bats remains unknown. Here, we determined this threshold for the vespertilionid bat Myotis daubentonii. We show that for a green luminous target, M. daubentonii has a visual luminance threshold of 3.2(±0.9)×10−4 cd m−2, an intensity corresponding to the luminance of an open cloudless terrestrial habitat on a starlit night. Our results show that echolocating bats have good visual sensitivity, allowing them to see during their active periods. Together with previous results showing that M. daubentonii has poor visual acuity (∼0.6 cycles deg−1), this suggests that echolocating bats do not use vision to hunt but rather to orient themselves.
  •  
46.
  • Cerenius, Lage, et al. (författare)
  • Commentary: variable immune molecules in invertebrates
  • 2013
  • Ingår i: Journal of Experimental Biology. - Company of Biologists Ltd : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 216:23, s. 4313-4319
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Recently it has become evident that invertebrates may mount a highly variable immune response that is dependent on which pathogen is involved. The molecular mechanisms behind this diversity are beginning to be unravelled and in several invertebrate taxa immune proteins exhibiting a broad range of diversity have been found. In some cases, evidence has been gathered suggesting that this molecular diversity translates into the ability of an affected invertebrate to mount a defence that is specifically aimed at a particular pathogen.
  •  
47.
  • Chakravarthi, Aravin, et al. (författare)
  • Differences in spatial resolution and contrast sensitivity of flight control in the honeybees Apis cerana and Apis mellifera
  • 2018
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 221:20
  • Tidskriftsartikel (refereegranskat)abstract
    • Visually guided behaviour is constrained by the capacity of the visual system to resolve detail. This, in turn, is limited by the spatial resolution and contrast sensitivity of the underlying visual system. Because these properties are interdependent and vary nonuniformly, it is only possible to fully understand the limits of a specific visually guided behaviour when they are investigated in combination. To understand the visual limits of flight control in bees, which rely heavily on vision to control flight, and to explore whether they vary between species, we tested how changes in spatial resolution and contrast sensitivity affect the speed and position control of the Asian and European honeybees (Apis cerana and Apis mellifera). Despite the apparent similarity of these species, we found some interesting and surprising differences between their visual limits. While the effect of spatial frequency and contrast on position control is similar between the species, ground speed is differently affected by these variables. A comparison with published data from the bumblebee Bombus terrestris revealed further differences. The visual resolution that limits the detection and use of optic flow for flight control in both species of honeybee is lower than the previously anatomically determined resolution and differs from object detection limits of A. mellifera, providing evidence that the limits of spatial resolution and contrast sensitivity are highly tuned to the particular behavioural task of a species.
  •  
48.
  • Chung, J S, et al. (författare)
  • Identification and developmental expression of mRNAs encoding crustacean cardioactive peptide (CCAP) in decapod crustaceans.
  • 2006
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 209:Pt 19, s. 3862-72
  • Tidskriftsartikel (refereegranskat)abstract
    • Full-length cDNAs encoding crustacean cardioactive peptide (CCAP) were isolated from several decapod (brachyuran and astacuran) crustaceans: the blue crab Callinectes sapidus, green shore crab Carcinus maenas, European lobster Homarus gamarus and calico crayfish Orconectes immunis. The cDNAs encode open reading frames of 143 (brachyurans) and 139-140 (astacurans) amino acids. Apart from the predicted signal peptides (30-32 amino acids), the conceptually translated precursor codes for a single copy of CCAP and four other peptides that are extremely similar in terms of amino acid sequence within these species, but which clearly show divergence into brachyuran and astacuran groups. Expression patterns of CCAP mRNA and peptide were determined during embryonic development in Carcinus using quantitative RT-PCR and immunohistochemistry with whole-mount confocal microscopy, and showed that significant mRNA expression (at 50% embryonic development) preceded detectable levels of CCAP in the developing central nervous system (CNS; at 70% development). Subsequent CCAP gene expression dramatically increased during the late stages of embryogenesis (80-100%), coincident with developing immunopositive structures. In adult crabs, CCAP gene expression was detected exclusively in the eyestalk, brain and in particular the thoracic ganglia, in accord with the predominance of CCAP-containing cells in this tissue. Measurement of expression patterns of CCAP mRNA in Carcinus and Callinectes thoracic ganglia throughout the moult cycle revealed only modest changes, indicating that previously observed increases in CCAP peptide levels during premoult were not transcriptionally coupled. Severe hypoxic conditions resulted in rapid downregulation of CCAP transcription in the eyestalk, but not the thoracic ganglia in Callinectes, and thermal challenge did not change CCAP mRNA levels. These results offer the first tantalising glimpses of involvement of CCAP in environmental adaptation to extreme, yet biologically relevant stressors, and perhaps suggest that the CCAP-containing neurones in the eyestalk might be involved in adaptation to environmental stressors.
  •  
49.
  • Claes, Julien, et al. (författare)
  • Nitric oxide in the control of luminescence from lantern shark (Etmopterus spinax)
  • 2010
  • Ingår i: JOURNAL OF EXPERIMENTAL BIOLOGY. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 213:17, s. 3005-3011
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract: Photophores (photogenic organs) of the lantern shark Etmopterus spinax are under hormonal control, with prolactin (PRL) and melatonin (MT) triggering the light emission. Differential sensitivity to these hormones in adult individuals suggests, however, that the luminescence of this shark is controlled by an additional mechanism. In this study, different techniques were used to investigate a potential modulator of E. spinax luminescence-nitric oxide (NO). NO synthase (NOS)-like immunoreactivity (IR) was found in the photocytes (photogenic cells) of the photophores. In addition, acetylated tubulin IR also supported the presence of nerves running through the photogenic tissue and innervating different structural elements of the photophores: photocytes, pigmented cells from the iris-like structure and lens cells. Pharmacological experiments confirmed a modulatory action of NO on the hormonally induced luminescence: NO donors sodium nitroprusside (SNP) and hydroxylamine decreased the time to reach the maximum amplitude (TLmax) of MT-induced luminescence while these substances decreased the maximum amplitude of PRL-induced luminescence (and also the TLmax in the case of SNP). The small impact of the NOS inhibitor L-NAME on hormonally induced luminescence suggests that NO is only produced on demand. The cGMP analogue 8BrcGMP mimicked the effects of NO donors suggesting that the effects of NO are mediated by cGMP.
  •  
50.
  • Clark, T. D., et al. (författare)
  • Aerobic scope measurements of fishes in an era of climate change: respirometry, relevance and recommendations
  • 2013
  • Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 216:15, s. 2771-2782
  • Forskningsöversikt (refereegranskat)abstract
    • Measurements of aerobic scope [the difference between minimum and maximum oxygen consumption rate ((M) over dot(O2,min) and (M) over dot(O2,max), respectively)] are increasing in prevalence as a tool to address questions relating to fish ecology and the effects of climate change. However, there are underlying issues regarding the array of methods used to measure aerobic scope across studies and species. In an attempt to enhance quality control before the diversity of issues becomes too great to remedy, this paper outlines common techniques and pitfalls associated with measurements of (M) over dot(O2,min), (M) over dot(O2,max) and aerobic scope across species and under different experimental conditions. Additionally, we provide a brief critique of the oxygen-and capacity-limited thermal tolerance (OCLTT) hypothesis, a concept that is intricately dependent on aerobic scope measurements and is spreading wildly throughout the literature despite little evidence for its general applicability. It is the intention of this paper to encourage transparency and accuracy in future studies that measure the aerobic metabolism of fishes, and to highlight the fundamental issues with assuming broad relevance of the OCLTT hypothesis.
  •  
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