| 1. |
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| 2. |
- Bianco, Giuseppe, et al.
(author)
-
Analysis of self-overlap reveals trade-offs in plankton swimming trajectories.
- 2014
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In: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5662 .- 1742-5689. ; 11:96
-
Journal article (peer-reviewed)abstract
- Movement is a fundamental behaviour of organisms that not only brings about beneficial encounters with resources and mates, but also at the same time exposes the organism to dangerous encounters with predators. The movement patterns adopted by organisms should reflect a balance between these contrasting processes. This trade-off can be hypothesized as being evident in the behaviour of plankton, which inhabit a dilute three-dimensional environment with few refuges or orienting landmarks. We present an analysis of the swimming path geometries based on a volumetric Monte Carlo sampling approach, which is particularly adept at revealing such trade-offs by measuring the self-overlap of the trajectories. Application of this method to experimentally measured trajectories reveals that swimming patterns in copepods are shaped to efficiently explore volumes at small scales, while achieving a large overlap at larger scales. Regularities in the observed trajectories make the transition between these two regimes always sharper than in randomized trajectories or as predicted by random walk theory. Thus, real trajectories present a stronger separation between exploration for food and exposure to predators. The specific scale and features of this transition depend on species, gender and local environmental conditions, pointing at adaptation to state and stage-dependent evolutionary trade-offs.
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| 3. |
- Bianco, Giuseppe, et al.
(author)
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Emlen funnel experiments revisited : methods update for studying compass orientation in songbirds
- 2016
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 6:19, s. 6930-6942
-
Journal article (peer-reviewed)abstract
- Migratory songbirds carry an inherited capacity to migrate several thousand kilometers each year crossing continental landmasses and barriers between distant breeding sites and wintering areas. How individual songbirds manage with extreme precision to find their way is still largely unknown. The functional characteristics of biological compasses used by songbird migrants has mainly been investigated by recording the birds directed migratory activity in circular cages, so-called Emlen funnels. This method is 50 years old and has not received major updates over the past decades. The aim of this work was to compare the results from newly developed digital methods with the established manual methods to evaluate songbird migratory activity and orientation in circular cages. We performed orientation experiments using the European robin (Erithacus rubecula) using modified Emlen funnels equipped with thermal paper and simultaneously recorded the songbird movements from above. We evaluated and compared the results obtained with five different methods. Two methods have been commonly used in songbirds’ orientation experiments; the other three methods were developed for this study and were based either on evaluation of the thermal paper using automated image analysis, or on the analysis of videos recorded during the experiment. The methods used to evaluate scratches produced by the claws of birds on the thermal papers presented some differences compared with the video analyses. These differences were caused mainly by differences in scatter, as any movement of the bird along the sloping walls of the funnel was recorded on the thermal paper, whereas video evaluations allowed us to detect single takeoff attempts by the birds and to consider only this behavior in the orientation analyses. Using computer vision, we were also able to identify and separately evaluate different behaviors that were impossible to record by the thermal paper. The traditional Emlen funnel is still the most used method to investigate compass orientation in songbirds under controlled conditions. However, new numerical image analysis techniques provide a much higher level of detail of songbirds’ migratory behavior and will provide an increasing number of possibilities to evaluate and quantify specific behaviors as new algorithms will be developed.
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| 4. |
- Bianco, Giuseppe, et al.
(author)
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Magnetic body alignment in migratory songbirds : a computer vision approach
- 2019
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In: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 222
-
Journal article (peer-reviewed)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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| 5. |
- Bianco, Giuseppe, et al.
(author)
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Magnetic storms disrupt nocturnal migratory activity in songbirds
- 2019
-
In: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 15:3
-
Journal article (peer-reviewed)abstract
- Birds possess a magnetic sense and rely on the Earth's magnetic field for orientation during migration. However, the geomagnetic field can be altered by solar activity at relative unpredictable intervals. How birds cope with the temporal geomagnetic variations caused by solar storms during migration is still unclear. We addressed this question by reproducing the effect of a solar storm on the geomagnetic field and monitoring the activity of three songbird species during autumn migration. We found that only the European robin reduced nocturnal migratory restlessness in response to simulated solar storms. At the same time, robins increased activity during early morning. We suggest that robins reduced activity at night when the perception of magnetic information would be strongly disrupted by temporal variations of the magnetic field, to extend their migration during daytime when several visual cues become available for orientation. The other two species, chiffchaff and dunnock, showing low or no nocturnal migratory activity, did not respond to the solar storm by changing activity.
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| 6. |
- Bianco, Giuseppe, et al.
(author)
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Plankton 3D tracking: the importance of camera calibration in stereo computer vision systems
- 2013
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In: Limnology and Oceanography: Methods. - : Wiley. - 1541-5856. ; 11, s. 278-286
-
Journal article (peer-reviewed)abstract
- Computer vision applications are very useful to study animal movements, but due to their intrinsic complexity they are challenging to design, implement, and use properly. We here describe a calibration procedure for a laboratory stereo vision system for tracking zooplankton in three dimensions (3D). We demonstrate the crucial importance of using a correct calibration for proper interpretation of animal swimming tracks. We also address the effect of the air-water shift phase in the calibration procedure. Actually, not performing a proper calibration caused an average positional error of more than 25 body-lengths in the investigated animal Daphnia magna. Furthermore, we evaluate the different outcomes of using 2D and 3D tracks obtained with a calibrated stereo vision system and show that although 2D tracking might be sufficient in some cases, the method was in our study unable to give information of swimming path geometry and underestimated the speed by 25%. Finally, we discuss consequences for biologically relevant questions when an incorrect methodology is used and strongly recommend that future studies provide detailed descriptions of the framework used for calibration to allow for comparisons between different studies.
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| 7. |
- Bianco, Giuseppe, et al.
(author)
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The importance of time of day for magnetic body alignment in songbirds
- 2022
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In: Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. - : Springer Science and Business Media LLC. - 0340-7594. ; 208:1, s. 135-144
-
Journal article (peer-reviewed)abstract
- Spontaneous magnetic alignment is the simplest known directional response to the geomagnetic field that animals perform. Magnetic alignment is not a goal directed response and its relevance in the context of orientation and navigation has received little attention. Migratory songbirds, long-standing model organisms for studying magnetosensation, have recently been reported to align their body with the geomagnetic field. To explore whether the magnetic alignment behaviour in songbirds is involved in the underlying mechanism for compass calibration, which have been suggested to occur near to sunset, we studied juvenile Eurasian reed warblers (Acrocephalus scirpaceus) captured at stopover during their first autumn migration. We kept one group of birds in local daylight conditions and an experimental group under a 2 h delayed sunset. We used an ad hoc machine learning algorithm to track the birds’ body alignment over a 2-week period. Our results show that magnetic body alignment occurs prior to sunset, but shifts to a more northeast–southwest alignment afterwards. Our findings support the hypothesis that body alignment could be associated with how directional celestial and magnetic cues are integrated in the compass of migratory birds.
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| 8. |
- Cerritelli, Giulia, et al.
(author)
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Assessing reliance on vector navigation in the long-distance oceanic migrations of green sea turtles
- 2019
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In: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 30:1, s. 68-79
-
Journal article (peer-reviewed)abstract
- Vector navigation, i.e., maintaining a constant heading for a given amount of time, is hypothesized to provide a viable basis for the navigational feats of a number of long-distance animal migrants. Since animals following this strategy are subject to drift by wind or by ocean current, performing long migrations relying on vector navigation is particularly challenging. We tested whether vector navigation could be involved in the migrations of green turtles (Chelonia mydas) that migrate between the remote Ascension Island and Brazil. To this aim, a novel approach was followed using individual-based numerical models to simulate migratory trajectories of virtual turtles that were compared to actual routes reconstructed by satellite. Simulated postnesting migrations from Ascension revealed that weak currents enabled modeled turtles to reach the Brazilian coast, but only for a limited range of headings around due West. This conclusion was corroborated by comparing modeled trajectories with the actual routes of previously tracked turtles, with a beeline vector navigation strategy providing the best fit, although a true-navigation strategy directed to the landfall site produced similar results. Finally, we tested if a vector navigational strategy was feasible for the prebreeding migration from Brazil towards Ascension, but modeled routes mostly failed to reach the island or a larger area around it, with individuals drifting away under the influence of currents. We conclude that Ascension turtles can take advantage of vector navigation when migrating towards a wide target like the Brazilian coast, while the demanding prebreeding migration likely requires more complex navigational systems.
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| 9. |
- Ekvall, Mikael T., et al.
(author)
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Behavioural responses to co-occurring threats of predation and ultraviolet radiation in Daphnia
- 2020
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In: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 65:9, s. 1509-1517
-
Journal article (peer-reviewed)abstract
- Organisms in the wild are faced with multiple threats and a common response is a change in behaviour. To disentangle responses to several threats, we exposed two differently sized species of the freshwater invertebrate Daphnia to solar ultraviolet radiation (UVR) and predation from either moving pelagic or benthic ambush predators. Using an advanced nanotechnology-based method, we tracked the three-dimensional movements of those mm-sized animals at the individual level. Each behavioural trial was performed both under conditions resembling night (no UVR) and day (UVR) and we examined patterns of the depth distribution and swimming speed by Daphnia across three treatments: no predator (control); bottom-dwelling damselfly (Calopteryx sp.); and fish (stickleback, Pungitius pungitius) predators. We also quantified the actual predation rate by the two predators on the two Daphnia species, Daphnia manga and Daphnia pulex. We show that individual Daphnia are able to identify predators with different feeding habitats, rank multiple and simultaneously occurring risks and respond in accordance with the actual threat; complex responses that are generally associated with larger animals. In a broader context, our results highlight and quantify how a cocktail of everyday threats is perceived and handled by invertebrates, which advances our understanding of species distribution in space and time, and thereby of population dynamics and ecosystem function in natural ecosystems.
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| 10. |
- Ekvall, Mikael, et al.
(author)
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Three-dimensional tracking of small aquatic organisms using fluorescent nanoparticles.
- 2013
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:11
-
Journal article (peer-reviewed)abstract
- Tracking techniques are vital for the understanding of the biology and ecology of organisms. While such techniques have provided important information on the movement and migration of large animals, such as mammals and birds, scientific advances in understanding the individual behaviour and interactions of small (mm-scale) organisms have been hampered by constraints, such as the sizes of existing tracking devices, in existing tracking methods. By combining biology, chemistry and physics we here present a method that allows three-dimensional (3D) tracking of individual mm-sized aquatic organisms. The method is based on in-vivo labelling of the organisms with fluorescent nanoparticles, so-called quantum dots, and tracking of the organisms in 3D via the quantum-dot fluorescence using a synchronized multiple camera system. It allows for the efficient and simultaneous study of the behaviour of one as well as multiple individuals in large volumes of observation, thus enabling the study of behavioural interactions at the community scale. The method is non-perturbing - we demonstrate that the labelling is not affecting the behavioural response of the organisms - and is applicable over a wide range of taxa, including cladocerans as well as insects, suggesting that our methodological concept opens up for new research fields on individual behaviour of small animals. Hence, this offers opportunities to focus on important biological, ecological and behavioural questions never before possible to address.
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| 11. |
- Fernández, Carla E., et al.
(author)
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Local adaptation to UV radiation in zooplankton : a behavioral and physiological approach
- 2020
-
In: Ecosphere. - : Wiley. - 2150-8925. ; 11:4
-
Journal article (peer-reviewed)abstract
- Ultraviolet radiation (UVR) is recognized as a driving force for phenotypic divergence. Here, we aim at assessing the ability of zooplankton to induce UVR tolerance and disentangle the relative importance of local adaptations behind the expression of such tolerance. Two populations of Daphnia pulex, derived from environments strongly differing in UVR conditions, were exposed to UVR for 70 d to induce production of photo-protective compounds and changes in behavioral responses. We expected greater tolerance to UVR in individuals from the high-UVR (H-U) environment as well as a refuge demand inversely related to the level of pigmentation. However, the complementarity between physiological and behavioral strategies was only observed on animals from the Low-UVR environment (L-U). L-U animals developed photo-protective compounds and decreased their refuge demand when re-exposed to UVR, that is, tolerated more UVR, compared to their control siblings. Conversely, UVR-exposed individuals from the H-U environment even having developed higher levels of photo-protective compounds increased their refuge demand staying deeper in the water column compared to the control animals, likely expressing an evolutionary memory to seek refuge in deeper waters irrespective of the UVR level. Stronger changes were observed in the H-U population compared to the L-U population; thus, our results suggest that although changes in tolerance after UVR exposure were evident for both populations, the strength of the inductions was more related to local adaptation independently of the rearing environment, showing that UVR tolerance is dependent on the evolutionary history of each population.
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| 12. |
- Hansson, Lars Anders, et al.
(author)
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Instantaneous threat escape and differentiated refuge demand among zooplankton taxa
- 2016
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In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 97:2, s. 279-285
-
Journal article (peer-reviewed)abstract
- Most animals, including aquatic crustacean zooplankton, perform strong avoidance movements when exposed to a threat, such as ultraviolet radiation (UVR). We here show that the genera Daphnia and Bosmina instantly adjust their vertical position in the water in accordance with the present UVR threat, i.e., seek refuge in deeper waters, whereas other taxa show less response to the threat. Moreover, Daphnia repeatedly respond to UVR pulses, suggesting that they spend more energy on movement than more stationary taxa, for example, during days with fluctuating cloud cover, illustrating nonlethal effects in avoiding UVR threat. Accordingly, we also show that the taxa with the most contrasting behavioral responses differ considerably in photoprotection, suggesting different morphological and behavioral strategies in handling the UVR threat. In a broader context, our studies on individual and taxa specific responses to UVR provide insights into observed spatial and temporal distribution in natural ecosystems.
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| 13. |
- Heuschele, Jan, et al.
(author)
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Context-dependent individual behavioral consistency in Daphnia
- 2017
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In: Ecosphere. - : John Wiley & Sons. - 2150-8925 .- 2150-8925. ; 8:2
-
Journal article (peer-reviewed)abstract
- The understanding of consistent individual differences in behavior, often termed “personality,” for adapting and coping with threats and novel environmental conditions has advanced considerably during the last decade. However, advancements are almost exclusively associated with higher-order animals, whereas studies focusing on smaller aquatic organisms are still rare. Here, we show individual differences in the swimming behavior of Daphnia magna, a clonal freshwater invertebrate, before, during, and after being exposed to a lethal threat, ultraviolet radiation (UVR). We show consistency in swimming velocity among both mothers and daughters of D. magna in a neutral environment, whereas this pattern breaks down when exposed to UVR. Our study also, for the first time, illustrates how the ontogenetic development in swimming and refuge-seeking behavior of young individuals eventually approaches that of adults. Overall, we show that aquatic invertebrates are far from being identical robots, but instead they show considerable individual differences in behavior that can be attributed to both ontogenetic development and individual consistency. Our study also demonstrates, for the first time, that behavioral consistency and repeatability, that is, something resembling “personality,” is context and state dependent in this zooplankter taxa.
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| 14. |
- Hollander, Johan, et al.
(author)
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Are assortative mating and genital divergence driven by reinforcement?
- 2018
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In: Evolution Letters. - : Oxford University Press (OUP). - 2056-3744. ; 2:6, s. 557-566
-
Journal article (peer-reviewed)abstract
- The evolution of assortative mating is a key part of the speciation process. Stronger assortment, or greater divergence in mating traits, between species pairs with overlapping ranges is commonly observed, but possible causes of this pattern of reproductive character displacement are difficult to distinguish. We use a multidisciplinary approach to provide a rare example where it is possible to distinguish among hypotheses concerning the evolution of reproductive character displacement. We build on an earlier comparative analysis that illustrated a strong pattern of greater divergence in penis form between pairs of sister species with overlapping ranges than between allopatric sister-species pairs, in a large clade of marine gastropods (Littorinidae). We investigate both assortative mating and divergence in male genitalia in one of the sister-species pairs, discriminating among three contrasting processes each of which can generate a pattern of reproductive character displacement: reinforcement, reproductive interference and the Templeton effect. We demonstrate reproductive character displacement in assortative mating, but not in genital form between this pair of sister species and use demographic models to distinguish among the different processes. Our results support a model with no gene flow since secondary contact and thus favor reproductive interference as the cause of reproductive character displacement for mate choice, rather than reinforcement. High gene flow within species argues against the Templeton effect. Secondary contact appears to have had little impact on genital divergence.
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| 15. |
- Hylander, Samuel, et al.
(author)
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Induced tolerance expressed as relaxed behavioural threat response in millimetre-sized aquatic organisms
- 2014
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In: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 281:1788, s. Article ID: 20140364-
-
Journal article (peer-reviewed)abstract
- Natural selection shapes behaviour in all organisms, but this is difficult to study in small, millimetre-sized, organisms. With novel labelling and tracking techniques, based on nanotechnology, we here show how behaviour in zooplankton (Daphnia magna) is affected by size, morphology and previous exposure to detrimental ultraviolet radiation (UVR). All individuals responded with immediate downward swimming to UVR exposure, but when released from the threat they rapidly returned to the surface. Large individuals swam faster and generally travelled longer distances than small individuals. Interestingly, individuals previously exposed to UVR (during several generations) showed a more relaxed response to UVR and travelled shorter total distances than those that were naive to UVR, suggesting induced tolerance to the threat. In addition, animals previously exposed to UVR also had smaller eyes than the naive ones, whereas UVR-protective melanin pigmentation of the animals was similar between populations. Finally, we show that smaller individuals have lower capacity to avoid UVR which could explain patterns in natural systems of lower migration amplitudes in small individuals. The ability to change behavioural patterns in response to a threat, in this case UVR, adds to our understanding of how organisms navigate in the ‘landscape of fear’, and this has important implications for individual fitness and for interaction strengths in biotic interactions.
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| 16. |
- Ilieva, Mihaela, et al.
(author)
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Does migratory distance affect fuelling in a medium-distance passerine migrant?: results from direct and step-wise simulated magnetic displacements.
- 2016
-
In: Biology Open. - : The Company of Biologists. - 2046-6390. ; 5, s. 272-278
-
Journal article (peer-reviewed)abstract
- In birds, fat accumulation before and during migration has been shown to be endogenously controlled and tuned by, among other factors, the Earth's magnetic field. However, our knowledge about the influence of the geomagnetic field on the fuelling in migrating birds is still limited to just a few nocturnally migrating passerine species. In order to study if variations of the magnetic field can also influence the fuelling of both day- and night-migrating passerines, we caught first-year dunnocks (Prunella modularis) and subjected them to three magnetic field conditions simulated by a system of magnetic coils: (1) local geomagnetic field of southern Sweden, (2) magnetic field corresponding to the centre of the expected wintering area, and (3) magnetic field met at the northern limit of the species' breeding distribution. We did not find a difference in mass increase between the birds kept in a local magnetic field and a field resembling their wintering area, irrespectively of the mode of magnetic displacement, i.e. direct or step-wise. However, the dunnocks magnetically displaced north showed a lower rate of fuelling in comparison to the control group, probably due to elevated activity. Compared with previous studies, our results suggest that the fuelling response to magnetic displacements during the migration period is specific to the eco-physiological situation. Future studies need to address if there is an effect of magnetic field manipulation on the level of migratory activity in dunnocks and how widespread the influence of local geomagnetic field parameters is on fuelling decisions in different bird species, which have different migratory strategies, distances and migration history.
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| 17. |
- Ilieva, Mihaela, et al.
(author)
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Effect of geomagnetic field on migratory activity in a diurnal passerine migrant, the dunnock, Prunella modularis
- 2018
-
In: Animal Behaviour. - : Elsevier BV. - 0003-3472. ; 146, s. 79-85
-
Journal article (peer-reviewed)abstract
- Migratory songbirds are guided by an endogenous programme during their first migration, encoding timing of migration, distance and direction. To successfully perform migration, birds have evolved phenotypic adaptations for flight, fuelling and navigation. Migratory distance in different species of birds is encoded as a period of expressed migratory restlessness, for which the length is correlated with migratory distance. Most of the work so far has been on nocturnal passerine migrants, while much less is known about the phenotypic adaptations for migration in diurnal migrants. Here we studied autumn migration fuelling and expression of migratory activity in caged diurnally migrating juvenile dunnocks in response to magnetic displacements. We kept one group (control) indoors at the location of capture in south Sweden, while the two experimental groups were gradually (over 5 days) displaced magnetically to locations to the northeast or to the wintering destination in southwest France. We found that all birds showed two peaks of activity during the day, for which the onset of activity was tightly timed to sunrise and sunset. The longest activity (2–3 h) occurred in the morning, coinciding with the natural period of migration for this species. For the control group, the migratory (flight) activity increased with the season (15 days), while it was strongly reduced for the dunnocks displaced to the wintering areas. Birds displaced to the north showed a stable, but slightly reduced migratory activity over time. The results support the finding that geomagnetic information expected to be met en route is important for triggering level of migratory activity in juveniles of a diurnal songbird migrant.
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| 18. |
- Ilieva, Mihaela, et al.
(author)
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Inherited differences of migratory phenotypes in two Acrocephalus warblers in relation to geomagnetic field parameters
- 2023
-
In: Behavioral Ecology and Sociobiology. - 0340-5443. ; 77:8
-
Journal article (peer-reviewed)abstract
- Abstract: Birds have evolved morphological, physiological and behavioural adaptations, encoded in their migratory programs, to enable successful migration. Sometimes, even closely related species, such as the Eurasian reed warbler and the sedge warbler, may adopt different migration strategies to reach their wintering grounds in sub-Saharan Africa. To study them in detail, we aimed to compare the temporal variations of activity patterns and fuelling of lab-held warblers caught in southern Sweden during autumn migration and compared the results with respect to known differences in their migration strategies. In order to investigate if the activity and fuelling were controlled by magnetic information, two groups of birds per species were experimentally subjected to magnetic fields anticipated during their migration via the Mediterranean and at the winter destinations, and control experiments were performed in the local magnetic field. Both species expressed a peak of nocturnal activity just after sunset and increased activity before sunrise. Reed warblers were strictly active during the night, whereas sedge warblers also showed increased morning activity possibly associated with intense foraging during stopover and longer migratory flights extending into the day when passing ecological barriers. There was no difference in overall activity between the two species but a change of active intervals during the experimental period with reed warblers increasing and sedge warblers decreasing activity over time, probably reflecting similar anticipated migration distances but differences in migratory strategies. The simulation of magnetic parameters influenced the activity and fuelling in reed warblers, but not in sedge warblers. These results support inherited differences in migratory strategies observed in the wild and suggest species-specific adaptations to magnetic field information regulating migration. Significance statement: Migratory birds often cover thousands of kilometres between their breeding and wintering sites. To successfully reach the destination, a bird may adopt a unique migration strategy including accumulation of fuel reserves and changes of diel activity pattern. Field observations have revealed how populations of birds perform their migrations; however, detailed monitoring of activity and fuelling over time for individual birds in a controlled setting is only possible in the laboratory. By using continuous video recording and automatic computer vision behavioural analysis, we quantified migratory activity patterns of two related species of warblers. We show that Eurasian reed warblers were strictly active during night, whereas sedge warblers also showed increased morning activity reflecting their migratory strategies observed in the wild. By simulating the magnetic field of sites along the migration route and wintering grounds, we found species-specific adaptations to magnetic field information.
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| 19. |
- Langer, Sina M., et al.
(author)
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A three-dimensional perspective of Daphnia’s swimming behavior with and without predator cues
- 2019
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In: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 64:4, s. 1515-1525
-
Journal article (peer-reviewed)abstract
- Behavioral adaptations play an important role in predator–prey interactions as they reduce predation risk. Prey organisms have therefore evolved a tremendous variability in behavioral adaptations. In case of small crustaceans of the genus Daphnia, which are common and important herbivores transferring energy from primary producers to higher trophic levels, such as predatory fish, and insects, altered migration patterns, swarming, or adaptive swimming speeds may increase survival rates. However, hitherto it has been difficult to analyze predator-induced behavioral adaptations as the small body size, as well as the low contrast between the transparent animals and their environment, most often impede behavioral movement analysis of individual animals. Therefore, we worked with a newly established technique providing higher contrast. We tagged daphniids with fluorescent nanoparticles and used a three-dimensional movement analysis system. We analyzed behavioral defense strategies of Daphnia clones from three species against different types of predators by measuring their behavior in presence and absence of predator cues. We analyzed swimming speed, depth selection, and motion patterns of Daphnia, as well as swarming behavior. We observed differences in the general swimming behavior in all analyzed aspects and show that daphniids change their behavioral strategies in the presence of predator cues, e.g., decrease their swimming speed as well as their vertical position or increase their nearest neighbor distance. Based on the observed changes in behavioral patterns, we conclude that the swimming behavior of daphniids may play an important role as inducible defense strategy that has the potential to improve prey survival chances.
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| 20. |
- Palmér, Tobias, et al.
(author)
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Calibration, Positioning and Tracking in a Refractive and Reflective Scene
- 2017
-
In: Pattern Recognition (ICPR), 2016 23rd International Conference on. - 9781509048472 ; , s. 3810-3815
-
Conference paper (peer-reviewed)abstract
- We propose a framework for calibration, positioningand tracking in a scene viewed by multiple cameras, througha flat refractive surface and one or several flat reflective walls.Refractions are explicitly modeled by Snell’s law and reflectionsare handled using virtual points. A novel bundle adjustmentframework is introduced for solving the nonlinear equationsof refractions and the linear equations of reflections, which inaddition enables optimization for calibration and positioning. Thenumerical accuracy of the solutions is investigated on syntheticdata, and the influence of noise in image points for several settingsof refractive and reflective planes is presented. The performance ofthe framework is evaluated on real data and confirms the validityof the physical model. Examples of how to use the frameworkto back-project image coordinates, forward-project scene pointsand estimate the refractive and reflective planes are presented.Lastly, an application of the system on real data from a biologicalexperiment on small aquatic organisms is presented.
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| 21. |
- Pastore, Raffaele, et al.
(author)
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Distinctive diffusive properties of swimming planktonic copepods in different environmental conditions
- 2018
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In: European Physical Journal E. Soft Matter. - : Springer Science and Business Media LLC. - 1292-8941 .- 1292-895X. ; 41:6
-
Journal article (peer-reviewed)abstract
- Abstract.: Suspensions of small planktonic copepods represent a special category in the realm of active matter, as their size falls within the range of colloids, while their motion is so complex that it cannot be rationalized according to basic models of self-propelled particles. Indeed, the wide range of individual variability and swimming patterns resemble the behaviour of much larger animals. By analysing hundreds of three-dimensional trajectories of the planktonic copepod Clausocalanus furcatus, we investigate the possibility of detecting how the motion of this species is affected by different external conditions, such as the presence of food and the effect of gravity. While this goal is hardly achievable by direct inspection of single organism trajectories, we show that this is possible by focussing on simple average metrics commonly used to characterize colloidal suspensions, such as the mean square displacement and the dynamic correlation functions. We find that the presence of food leads to the onset of a clear localization that separates a short-time ballistic from a long-time diffusive regime. Such a benchmark reflects the tendency of C. furcatus to remain temporally feeding in a limited space and disappears when food is absent. Localization is clearly evident in the horizontal plane, but is negligible in the vertical direction, due to the effect of gravity. Our results suggest that simple average descriptors may provide concise and useful information on the swimming properties of planktonic copepods, even though single organism behaviour is strongly heterogeneous. Graphical abstract: [Figure not available: see fulltext.].
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| 22. |
- Scarlata, Simone, et al.
(author)
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Advancing healthcare through thoracic ultrasound research in older patients
- 2023
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In: Aging Clinical and Experimental Research. - 1594-0667 .- 1720-8319. ; 35:12, s. 2887-2901
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Research review (peer-reviewed)abstract
- This paper reports the proceedings of a meeting convened by the Research Group on Thoracic Ultrasound in Older People of the Italian Society of Gerontology and Geriatrics, to discuss the current state-of-the-art of clinical research in the field of geriatric thoracic ultrasound and identify unmet research needs and potential areas of development. In the last decade, point-of-care thoracic ultrasound has entered clinical practice for diagnosis and management of several respiratory illnesses, such as bacterial and viral pneumonia, pleural effusion, acute heart failure, and pneumothorax, especially in the emergency–urgency setting. Very few studies, however, have been specifically focused on older patients with frailty and multi-morbidity, who frequently exhibit complex clinical pictures needing multidimensional evaluation. At the present state of knowledge, there is still uncertainty on the best requirements of ultrasound equipment, methodology of examination, and reporting needed to optimize the advantages of thoracic ultrasound implementation in the care of geriatric patients. Other issues regard differential diagnosis between bacterial and aspiration pneumonia, objective grading of interstitial syndrome severity, quantification and monitoring of pleural effusions and solid pleural lesions, significance of ultrasonographic assessment of post-COVID-19 sequelae, and prognostic value of assessment of diaphragmatic thickness and motility. Finally, application of remote ultrasound diagnostics in the community and nursing home setting is still poorly investigated by the current literature. Overall, the presence of several open questions on geriatric applications of thoracic ultrasound represents a strong call to implement clinical research in this field.
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| 23. |
- Sokolovskis, Kristaps, et al.
(author)
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Ten grams and 13,000km on the wing - route choice in willow warblers Phylloscopus trochilus yakutensis migrating from Far East Russia to East Africa
- 2018
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In: Movement Ecology. - : Springer Science and Business Media LLC. - 2051-3933. ; 6:1
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Journal article (peer-reviewed)abstract
- Background: High-latitude bird migration has evolved after the last glaciation, in less than 10,000-15,000years. Migrating songbirds rely on an endogenous migratory program, encoding timing, fueling, and routes, but it is still unknown which compass mechanism they use on migration. We used geolocators to track the migration of willow warblers (Phylloscopus trochilus yakutensis) from their eastern part of the range in Russia to wintering areas in sub-Saharan Africa. Our aim was to investigate if the autumn migration route can be explained by a simple compass mechanism, based on celestial or geomagnetic information, or whether migration is undertaken as a sequence of differential migratory paths possibly involving a map sense. We compared the recorded migratory routes for our tracked birds with simulated routes obtained from different compass mechanisms. Results: The three tracked males were very similar in the routes they took to their final wintering sites in southern Tanzania or northern Mozambique, in their use of stopover sites and in the overall timing of migration. None of the tested compass mechanisms could explain the birds' routes to the first stopover area in southwest Asia or to the destination in Southeast Africa without modifications. Our compass mechanism simulations suggest that the simplest scenarios congruent with the observed routes are based on either an inclination or a sun compass, assuming two sequential steps. Conclusions: The birds may follow a magnetoclinic route coinciding closely with the tracks by first moving west, i.e. closer to the goal, and thereafter follow a constant apparent angle of inclination to the stopover site. An alternative would be to use the sun compass, but with time-adjustments along the initial part of the migration to the first stopover, and thereafter depart along a new course to the winter destination. A combination of the two mechanisms cannot be ruled out, but needs to be confirmed in future studies.
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| 24. |
- Tavaglione, Federica, et al.
(author)
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Development and Validation of a Score for Fibrotic Non-Alcoholic Steatohepatitis.
- 2023
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In: Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association. - : Elsevier BV. - 1542-7714. ; 21:6, s. 1523-1532
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Journal article (peer-reviewed)abstract
- Non-invasive assessment of histological features of non-alcoholic fatty liver disease (NAFLD) has been an intensive research area over the last decade. Herein, we aimed to develop a simple non-invasive score using routine laboratory tests to identify, among individuals at high risk for NAFLD, those with fibrotic non-alcoholic steatohepatitis (NASH) defined as NASH, NAFLD activity score (NAS) ≥4, and fibrosis stage ≥2.The derivation cohort included 264 morbidly obese individuals undergoing intraoperative liver biopsy in Rome, Italy. The best predictive model was developed and internally validated using a bootstrapping stepwise logistic regression analysis (2000 bootstrap samples). Performance was estimated by the area under the receiver operating characteristic curve (AUROC). External validation was assessed in three independent European cohorts (Finland, n=370; Italy n=947; England n=5,368) of individuals at high risk for NAFLD.The final predictive model, designated as Fibrotic NASH Index (FNI), combined aspartate aminotransferase (AST), high-density lipoprotein (HDL) cholesterol, and hemoglobin A1c (HbA1c). The performance of FNI for fibrotic NASH was satisfactory in both derivation and external validation cohorts (AUROCs 0.78 and 0.80-0.95, respectively). In the derivation cohort, rule-out and rule-in cut-offs were 0.10 for sensitivity ≥0.89 (negative predictive value [NPV] 0.93) and 0.33 for specificity ≥0.90 (positive predictive value [PPV] 0.57), respectively. In the external validation cohorts, sensitivity ranged from 0.87 to 1 (NPV 0.99-1) and specificity from 0.73 to 0.94 (PPV 0.12-0.49) for rule-out and rule-in cut-off, respectively.FNI is an accurate, simple, and affordable non-invasive score which can be used in primary healthcare to screen for fibrotic NASH individuals with dysmetabolism.
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| 25. |
- Uttieri, Marco, et al.
(author)
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Homeostatic swimming of zooplankton upon crowding : The case of the copepod Centropages typicus
- 2021
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In: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5689 .- 1742-5662. ; 18:179
-
Journal article (peer-reviewed)abstract
- Crowding has a major impact on the dynamics of many material and biological systems, inducing effects as diverse as glassy dynamics and swarming. While this issue has been deeply investigated for a variety of living organisms, more research remains to be done on the effect of crowding on the behaviour of copepods, the most abundant metazoans on Earth. To this aim, we experimentally investigate the swimming behaviour, used as a dynamic proxy of animal adaptations, of males and females of the calanoid copepod Centropages typicus at different densities of individuals (10, 50 and 100 ind. l -1) by performing three-dimensional single-organism tracking. We find that the C. typicus motion is surprisingly unaffected by crowding over the investigated density range. Indeed, the mean square displacements as a function of time always show a crossover from ballistic to Fickian regime, with poor variations of the diffusion constant on increasing the density. Close to the crossover, the displacement distributions display exponential tails with a nearly density-independent decay length. The trajectory fractal dimension, D 3D ≅ 1.5, and the recently proposed 'ecological temperature' also remain stable on increasing the individual density. This suggests that, at least over the range of animal densities used, crowding does not impact on the characteristics of C. typicus swimming motion, and that a homeostatic mechanism preserves the stability of its swimming performance.
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| 26. |
- Zhao, Guangyu, et al.
(author)
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Inelastic hyperspectral lidar for aquatic ecosystems monitoring and landscape plant scanning test
- 2018
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In: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 176
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Journal article (peer-reviewed)abstract
- We have developed an aquatic inelastic hyperspectral lidar with unrestricted focal-depth and enough sensitivity and spatio-temporal resolution to detect and resolve position and behavior of individual sub-millimeter aquatic organisms. We demonstrate ranging with monitoring of elastic echoes, water Raman signals and fluorescence from chlorophyllbearing phytoplankton and dye tagged organisms. The system is based on a blue CW diode laser and a Scheimpflug optical arrangement.
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| 27. |
- Zhao, Guangyu, et al.
(author)
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Inelastic hyperspectral lidar for profiling aquatic ecosystems
- 2016
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In: Laser and Photonics Reviews. - : Wiley. - 1863-8880. ; 10:5, s. 807-813
-
Journal article (peer-reviewed)abstract
- Monitoring the aquatic environment and the life of free-floating organisms remains on the borderline of our technical capabilities. Therefore, our insights into aquatic habitats, such as, abundance and behavior of organisms are limited. In order to improve our understanding of aquatic life, we have developed a low-cost inelastic hyperspectral lidar with unlimited focal depth and enough sensitivity and spatiotemporal resolution to detect and resolve position and behavior of individual submillimeter organisms. In this work, we demonstrate elastic as well as molecular ranging by using the water Raman band, and by observing fluorescence from chlorophyll and from dye-tagged organisms. We present an aquatic laser-diode-based inelastic light detection and ranging (lidar) system with unprecedented sensitivity, spatiotemporal resolution and number of spectral bands. Our system offers new opportunities for quantitative in situ studies of aquatic organisms, and has the potential to considerably advance our understanding of biological life in aquatic systems. (Figure presented.).
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| 28. |
- Åkesson, Susanne, et al.
(author)
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Assessing vector navigation in long-distance migrating birds
- 2016
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In: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 27:3, s. 865-875
-
Journal article (peer-reviewed)abstract
- Birds migrating between distant locations regularly perform long continuous flights lasting several days. What compass mechanism they use is still a mystery. Here, we use a novel approach, applying an individual-based model, taking compass mechanisms based on celestial and geomagnetic information and wind into account simultaneously, to investigate what compass mechanism likely is used during long continuous flights and how wind drift or compensation affects the resulting tracks. We found that for the 6 cases of long continuous migration flights, the magnetoclinic route could best explain the route selection in all except one case compared with the alternative compass mechanisms. A flight strategy correcting for wind drift resulted most often in routes ending up closest to the predicted destinations. In only half of the cases could a time-compensated sun compass explain the migration routes observed with sufficient precision. Migration from Europe to the Siberian tundra was especially challenging to explain by one compass mechanism alone, suggesting a more complex navigation strategy. Our results speak in favor of a magnetic compass based on the angle of inclination used by birds during continuous long-distance migration flights, but also a capacity to detect and correct for drift caused by winds along the route.
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| 29. |
- Åkesson, Susanne, et al.
(author)
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Autumn migratory orientation and route choice in early and late dunlins Calidris alpina captured at a stopover site in Alaska
- 2021
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In: Biology open. - : The Company of Biologists Ltd. - 2046-6390. ; 10:4, s. 1-10
-
Journal article (peer-reviewed)abstract
- We investigated the migratory orientation of early and late captured dunlins, Calidris alpina, by recording their migratory activity in circular orientation cages during autumn at a staging site in southwest Alaska and performed route simulations to the wintering areas. Two races of dunlins breeding in Alaska have different wintering grounds in North America (Pacific Northwest), and East Asia. Dunlins caught early in autumn (presumably Calidris alpina pacifica) oriented towards their wintering areas (east-southeast; ESE) supporting the idea that they migrate nonstop over the Gulf of Alaska to the Pacific Northwest. We found no difference in orientation between adult and juveniles, nor between fat and lean birds or under clear and overcast skies demonstrating that age, energetic status and cloud cover did not affect the dunlins' migratory orientation. Later in autumn, we recorded orientation responses towards south-southwest suggesting arrival of the northern subspecies Calidris alpina arcticola at our site. Route simulations revealed multiple compass mechanisms were compatible with the initial direction of early dunlins wintering in the Pacific Northwest, and for late dunlins migrating to East Asia. Future high-resolution tracking would reveal routes, stopover use including local movements and possible course shifts during migration from Alaska to wintering sites on both sides of the north Pacific Ocean.
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| 30. |
- Åkesson, Susanne, et al.
(author)
-
Autumn migratory orientation and route choice in early and late dunlins Calidris alpina captured at a stopover site in Alaska
- 2021
-
In: Biology Open. - : The Company of Biologists. - 2046-6390. ; 10:4
-
Journal article (peer-reviewed)abstract
- We investigated the migratory orientation of early and late captured dunlins, Calidris alpina, by recording their migratory activity in circular orientation cages during autumn at a staging site in southwest Alaska and performed route simulations to the wintering areas. Two races of dunlins breeding in Alaska have different wintering grounds in North America (Pacific Northwest), and East Asia. Dunlins caught early in autumn (presumably Calidris alpinapacifica) oriented towards their wintering areas (east-southeast; ESE) supporting the idea that they migrate nonstop over the Gulf of Alaska to the Pacific Northwest. We found no difference in orientation between adult and juveniles, nor between fat and lean birds or under clear and overcast skies demonstrating that age, energetic status and cloud cover did not affect the dunlins' migratory orientation. Later in autumn, we recorded orientation responses towards south-southwest suggesting arrival of the northern subspecies Calidris alpinaarcticola at our site. Route simulations revealed multiple compass mechanisms were compatible with the initial direction of early dunlins wintering in the Pacific Northwest, and for late dunlins migrating to East Asia. Future high-resolution tracking would reveal routes, stopover use including local movements and possible course shifts during migration from Alaska to wintering sites on both sides of the north Pacific Ocean.
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| 31. |
- Åkesson, Susanne, et al.
(author)
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Flexibility and Control of Circadian Activity, Migratory Restlessness and Fueling in Two Songbird Migrants
- 2021
-
In: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 9
-
Journal article (peer-reviewed)abstract
- Juvenile songbirds rely on an endogenous program, encoding direction, distance, fueling, and timing of migration. Migratory distance is species-specific, expressed as a period of migratory restlessness, for which the length is correlated with distance, while fueling is modified to meet anticipated flight distances controlled by geomagnetic cues and amount of day-light available for foraging. How daylength affect onset and level of migratory activity and fueling decisions in wild birds have so far received limited attention. Here we study how photoperiod controls onset, level and extent of autumn migratory activity and fueling in juvenile diurnally migrating dunnocks, and nocturnally migrating European robins by experimentally increasing daylength. For both species, we kept a control group indoors at the location of capture in southern Sweden exposed to the natural photoperiod, and an experimental group with increased and advanced photoperiod by 2 h in the morning. Dunnocks initiated migratory activity at sunrise (or artificial sunrise) in both groups, demonstrating a highly responsive and flexible component for the onset of migration triggered by light. Experimental robins anticipated the end of nocturnal migratory activity predicting the earlier sunrise immediately after the time-shift and expressed this behavior already under darkness, supporting a fast-resetting mechanism to the new diel period. Timing of end of morning activity was not affected by the earlier sunrise in both species, suggesting a fixed endogenous control that persisted throughout the 13-day study period. Experimental dunnocks expressed higher overall activity and lower fuel loads than controls, while robins did not change their overall activity and fuel load in response to the shifted and increased photoperiod. These results reveal important adaptations for circadian timekeeping including both a flexible onset open to fast modifications and a more rigid end, with differential effects by the treatment on migratory activity and fueling in the two species.
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| 32. |
- Åkesson, Susanne, et al.
(author)
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Migratory orientation in inexperienced and experienced avian migrants
- 2021
-
In: Ethology Ecology and Evolution. - : Informa UK Limited. - 0394-9370 .- 1828-7131. ; 33:3, s. 206-229
-
Research review (peer-reviewed)abstract
- Massive bird migration across continents and seas is one of the most spectacular phenomena in nature, involving billions of birds annually. In the autumn, most birds on migration are juveniles migrating for the first time while adults are repeating their migrations. Migration syndrome in individual bird migrants involves multiple behavioural, morphological and physiological adaptations, and migration performance may improve with experience and age. In this review, we discuss in what ways young and adult birds differ with respect to migration performance and compass orientation during migration, how they respond to external information including topography and winds during migration, and what phenotypic characteristics related to migratory behaviour may change over a lifetime in individual birds. Here, we present the prevailing concepts of navigation, including compass mechanisms leading birds across the globe to predictable goals, and the underlying sources of variability within and between individuals and age groups. In particular, we focus on what changes in the endogenous migration program may lead to more efficient realizations of migration with age. We review our data combined with other data presented in the literature, based on different techniques to study the migration phenotype expression in caged and free-flying birds with different migratory adaptations. The widespread use of tracking technology to study birds in different environments and geographical areas has largely contributed to our current knowledge on how migration performance improves with age. Still, there is a need to understand in more detail how migration performance, timing and route choices develop across time in individual migrants, and what navigational information is used to guide birds across the globe from the first and following migrations.
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| 33. |
- Åkesson, Susanne, et al.
(author)
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Negotiating an ecological barrier : Crossing the Sahara in relation to winds by common swifts
- 2016
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In: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 371:1704
-
Journal article (peer-reviewed)abstract
- The Sahara Desert is one of the largest land-based barriers on the Earth, crossed twice each year by billions of birds on migration. Here we investigate how common swifts migrating between breeding sites in Sweden and wintering areas in sub-Saharan Africa perform the desert crossing with respect to route choice, winds, timing and speed of migration by analysing 72 geolocator tracks recording migration. The swifts crosswestern Sahara on a broad front in autumn, while in spring they seem to use three alternative routes across the Sahara, awestern, a central and an eastern route across the Arabian Peninsula, with most birds using the western route. The swifts show slower migration and travel speeds, and make longer detours with more stops in autumn compared with spring. In spring, the stopover period in West Africa coincided with mostly favourable winds, but birds remained in the area, suggesting fuelling. The western route provided more tailwind assistance compared with the central route for our tracked swifts in spring, but not in autumn. The ultimate explanation for the evolution of a preferred western route is presumably a combination of matching rich foraging conditions (swarming insects) and favourable winds enabling fast spring migration.
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| 34. |
- Åkesson, Susanne, et al.
(author)
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Route simulations, compass mechanisms and long-distance migration flights in birds
- 2017
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In: Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. - : Springer Science and Business Media LLC. - 0340-7594. ; 203:6-7, s. 475-490
-
Journal article (peer-reviewed)abstract
- Bird migration has fascinated humans for centuries and routes crossing the globe are now starting to be revealed by advanced tracking technology. A central question is what compass mechanism, celestial or geomagnetic, is activated during these long flights. Different approaches based on the geometry of flight routes across the globe and route simulations based on predictions from compass mechanisms with or without including the effect of winds have been used to try to answer this question with varying results. A major focus has been use of orthodromic (great circle) and loxodromic (rhumbline) routes using celestial information, while geomagnetic information has been proposed for both a magnetic loxodromic route and a magnetoclinic route. Here, we review previous results and evaluate if one or several alternative compass mechanisms can explain migration routes in birds. We found that most cases could be explained by magnetoclinic routes (up to 73% of the cases), while the sun compass could explain only 50%. Both magnetic and geographic loxodromes could explain <25% of the routes. The magnetoclinic route functioned across latitudes (1°S–74°N), while the sun compass only worked in the high Arctic (61–69°N). We discuss the results with respect to orientation challenges and availability of orientation cues.
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| 35. |
- Åkesson, Susanne, et al.
(author)
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Wind-assisted sprint migration in northern swifts
- 2021
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In: iScience. - : Elsevier BV. - 2589-0042. ; 24:6
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Journal article (peer-reviewed)abstract
- Long-distance migration has evolved repeatedly in animals and covers substantial distances across the globe. The overall speed of migration in birds is determined by fueling rate at stopover, flight speed, power consumption during flight, and wind support. The highest speeds (500 km/day) have been predicted in small birds with a fly-and-forage strategy, such as swallows and swifts. Here, we use GLS tracking data for common swifts breeding in the northern part of the European range to study seasonal migration strategies and overall migration speeds. The data reveal estimated overall migration speeds substantially higher (average: 570 km/day; maximum: 832 km/day over 9 days) than predicted for swifts. In spring, swift routes provided 20% higher tailwind support than in autumn. Sustained migration speeds of this magnitude can only be achieved in small birds by a combined strategy including high fueling rate at stopover, fly-and-forage during migration, and selective use of tailwinds.
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