| 1. |
- Eriksson, Maertha, et al.
(författare)
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Insect brain plasticity : effects of olfactory input on neuropil size
- 2019
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- Insect brains are known to express a high degree of experience-dependent structural plasticity. One brain structure in particular, the mushroom body (MB), has been attended to in numerous studies as it is implicated in complex cognitive processes such as olfactory learning and memory. It is, however, poorly understood to what extent sensory input per se affects the plasticity of the mushroom bodies. By performing unilateral blocking of olfactory input on immobilized butterflies, we were able to measure the effect of passive sensory input on the volumes of antennal lobes (ALs) and MB calyces. We showed that the primary and secondary olfactory neuropils respond in different ways to olfactory input. ALs show absolute experience-dependency and increase in volume only if receiving direct olfactory input from ipsilateral antennae, while MB calyx volumes were unaffected by the treatment and instead show absolute age-dependency in this regard. We therefore propose that cognitive processes related to behavioural expressions are needed in order for the calyx to show experience-dependent volumetric expansions. Our results indicate that such experience-dependent volumetric expansions of calyces observed in other studies may have been caused by cognitive processes rather than by sensory input, bringing some causative clarity to a complex neural phenomenon.
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| 2. |
- Eriksson, Maertha, et al.
(författare)
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Structural plasticity of olfactory neuropils in relation to insect diapause
- 2020
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 10:24, s. 14423-14434
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Tidskriftsartikel (refereegranskat)abstract
- Many insects that live in temperate zones spend the cold season in a state of dormancy, referred to as diapause. As the insect must rely on resources that were gathered before entering diapause, keeping a low metabolic rate is of utmost importance. Organs that are metabolically expensive to maintain, such as the brain, can therefore become a liability to survival if they are too large. Insects that go through diapause as adults generally do so before entering the season of reproduction. This order of events introduces a conflict between maintaining low metabolism during dormancy and emerging afterward with highly developed sensory systems that improve fitness during the mating season. We investigated the timing of when investments into the olfactory system are made by measuring the volumes of primary and secondary olfactory neuropils in the brain as they fluctuate in size throughout the extended diapause life-period of adult Polygonia c-album butterflies. Relative volumes of both olfactory neuropils increase significantly during early adult development, indicating the importance of olfaction to this species, but still remain considerably smaller than those of nondiapausing conspecifics. However, despite butterflies being kept under the same conditions as before the dormancy, their olfactory neuropil volumes decreased significantly during the postdormancy period. The opposing directions of change in relative neuropil volumes before and after diapause dormancy indicate that the investment strategies governing structural plasticity during the two life stages could be functionally distinct. As butterflies were kept in stimulus-poor conditions, we find it likely that investments into these brain regions rely on experience-expectant processes before diapause and experience-dependent processes after diapause conditions are broken. As the shift in investment strategies coincides with a hard shift from premating season to mating season, we argue that these developmental characteristics could be adaptations that mitigate the trade-off between dormancy survival and reproductive fitness.
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| 3. |
- Larsdotter-Mellström, Helena, et al.
(författare)
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It's All in the Mix : Blend-Specific Behavioral Response to a Sexual Pheromone in a Butterfly
- 2016
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Ingår i: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Among insects, sexual pheromones are typically mixtures of two to several components, all of which are generally required to elicit a behavioral response. Here we show for the first time that a complete blend of sexual pheromone components is needed to elicit a response also in a butterfly. Males of the Green-veined White, Pieris napi, emit an aphrodisiac pheromone, citral, from wing glands. This pheromone is requisite for females to accept mating with a courting male. Citral is a mixture of the two geometric isomers geranial (E-isomer) and neral (Z-isomer) in an approximate 1:1 ratio. We found that both these compounds are required to elicit acceptance behavior, which indicates synergistic interaction between processing of the isomers. Using functional Ca2+ imaging we found that geranial and neral evoke significantly different but overlapping glomerular activity patterns in the antennal lobe, which suggests receptors with different affinity for the two isomers. However, these glomeruli were intermingled with glomeruli responding to, for example, plant-related compounds, i.e., no distinct subpopulation of pheromone-responding glomeruli as in moths and other insects. In addition, these glomeruli showed lower specificity than pheromone-activated glomeruli in moths. We could, however, not detect any mixture interactions among four identified glomeruli, indicating that the synergistic effect may be generated at a higher processing level. Furthermore, correlations between glomerular activity patterns evoked by the single isomers and the blend did not change over time.
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| 4. |
- Larsdotter-Mellström, Helena, et al.
(författare)
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Male butterflies use an anti-aphrodisiac pheromone to tailor ejaculates
- 2016
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 30:2, s. 255-261
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Tidskriftsartikel (refereegranskat)abstract
- When females mate with multiple partners, the risk of sperm competition depends on female mating history. To maximize fitness, males should adjust their mating investment according to this risk. In polyandrous butterflies, males transfer a large, nutritious ejaculate at mating. Larger ejaculates delay female remating and confer an advantage in sperm competition. We test whether male ejaculate size in the butterfly Pieris napi (Lepidoptera) varies with female mating history and thus sperm competition, and whether males assess sperm competition using the male-transferred anti-aphrodisiac methyl salicylate (MeS) as a cue. Both sexes responded physiologically to MeS in a dose-dependent manner. Males, however, were more sensitive to MeS than females. Ejaculates transferred by males mating with previously mated females were on average 26% larger than ejaculates transferred by males mating with virgin females, which conforms to sperm competition theory and indicates that males tailored their reproductive investment in response to sperm competition. Furthermore, ejaculates transferred by males mating with virgin females with artificially added MeS were also 26% larger than ejaculates transferred to control virgin females. Male-transferred anti-aphrodisiac pheromone not only functions as a male deterrent, but also carries information on female mating history and thus allows males to assess sperm competition.
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| 5. |
- Lehmann, Philipp, et al.
(författare)
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Idiosyncratic development of sensory structures in brains of diapausing butterfly pupae : implications for information processing
- 2017
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 284:1858
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Tidskriftsartikel (refereegranskat)abstract
- Diapause is an important escape mechanism from seasonal stress in many insects. A certain minimum amount of time in diapause is generally needed in order for it to terminate. The mechanisms of time-keeping in diapause are poorly understood, but it can be hypothesized that a well-developed neural system is required. However, because neural tissue is metabolically costly to maintain, there might exist conflicting selective pressures on overall brain development during diapause, on the one hand to save energy and on the other hand to provide reliable information processing during diapause. We performed the first ever investigation of neural development during diapause and non-diapause (direct) development in pupae of the butterfly Pieris napi from a population whose diapause duration is known. The brain grew in size similarly in pupae of both pathways up to 3 days after pupation, when development in the diapause brain was arrested. While development in the brain of direct pupae continued steadily after this point, no further development occurred during diapause until temperatures increased far after diapause termination. Interestingly, sensory structures related to vision were remarkably well developed in pupae from both pathways, in contrast with neuropils related to olfaction, which only developed in direct pupae. The results suggest that a well-developed visual system might be important for normal diapause development.
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| 6. |
- Schäpers, Alexander, et al.
(författare)
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Specialist and generalist oviposition strategies in butterflies : maternal care or precocious young?
- 2016
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 180:2, s. 335-343
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Tidskriftsartikel (refereegranskat)abstract
- Herbivorous insects specialized on a narrow set of plants are believed to be better adapted to their specific hosts. This hypothesis is supported by observations of herbivorous insect species with a broader diet breadth which seemingly pay a cost through decreased oviposition accuracy. Despite many studies investigating female oviposition behavior, there is a lack of knowledge on how larvae cope behaviorally with their mothers' egg-laying strategies. We have examined a unique system of five nymphalid butterfly species with different host plant ranges that all feed on the same host plant. The study of this system allowed us to compare at the species level how oviposition preference is related to neonate larval responses in several disadvantageous situations. We found a general co-adaptation between female and larval abilities, where species with more discriminating females had larvae that were less able to deal with a suboptimal initial feeding site. Conversely, relatively indiscriminate females had more precocious larvae with better abilities to cope with suboptimal sites. Despite similarities between the tested species with similar host ranges, there were also striking differences. Generalist and specialist species can be found side by side in many clades, with each clade having a specific evolutionary history. Such clade-specific, phylogenetically determined preconditions apparently have affected how precisely a broad or narrow diet breadth can be realized.
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