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Factors affecting the colour changing behaviour of three-spined sticklebacks (Gasterosteus aculeatus)
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
2019 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

The ability to change colour is an important adaptation for animals that live in heterogeneous environments. There is a lot of knowledge about physiological processes that contribute to behavioural changes in body colouration, but individual variation is less well-understood. In three-spined sticklebacks (Gasterosteus aculeatus) there is an individual variability in the degree of colour change and individuals are consistent over time in how much they change colour. My study aimed to investigate whether there is individual variability also in the rate with which colour change occur, and whether this trait is related to the degree of colour change in vivo (behavioural colour change) as well as to the physiological colour changing properties of skin cells in vitro (physiological colour change). I also investigated how body size and infection of the parasites Schistocephalus solidus and Glugea spp., affect the colour changing behaviour and how and an individual's colour change relates to its boldness.

Three-spined sticklebacks (n=64) were exposed to a change in the background (from black to white) in order to examine the behaviour to adaptively change colour by becoming more pale. The colour changing behaviour was video recorded using a 4K high resolution camera and individual frames were analyzed in Adobe Photoshop using CIE L*a*b* colour space. The sticklebacks underwent a test in order to measure the individual boldness, measured as the latency to emerge from a refuge. Chromatophores are pigment cells that are responsible for the great diversity, and the flexibility, of colouration in several taxa, including fishes. After the behavioural trials, the fish were euthanized, and skin biopsies were excised from each individual and placed in either noradrenaline (NA) or alpha- melanocyte stimulating hormone (α-MSH). These hormones cause opposing responses in chromatophores, which allowed me to study the physiological processes underlying colour change. The solutions (NA and α-MSH) aimed to induce maximal pigment aggregation or dispersion, respectively. The degree and rate of this in vitro physiological colour change was estimated by digital image analysis.

There was individual variation in both the degree and the rate of colour change, both when analyzing the behaviour (live fish) and using biopsies. However, there was no relationship in the degree of colour change between the behavioural and physiological measurements, nor was there such a relationship for the rate of the colour change. Thus, the behaviour of changing colour did not seem to be limited by the physiological capacity to do so. Sticklebacks that changed their colour to a great degree, also tended to do this at a faster rate. This relationship was found both in vivo and in vitro. Smaller sticklebacks changed colour to a greater degree and fish with a smaller body mass were also faster. In addition, smaller fish had biopsies that changed colour to a greater degree and at a faster rate. The boldness test showed that individuals that had a physiological capacity to change colour to a greater degree, and at a faster rate, were also bolder. My results contribute to the understanding of the relationship between behavioural- and physiological aspects of colour changing behaviour in sticklebacks. In addition, I developed novel methods which are suitable for future studies of colour changing behaviour in fishes.

Place, publisher, year, edition, pages
2019. , p. 31
Keywords [en]
Colour changing behaviour, Background matching, Boldness-test, Skin biopsy, Gasterosteus aculeatus, Noradrenaline (NA), α-Melanocyte stimulating hormone (α-MSH)
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Other Biological Topics
Identifiers
URN: urn:nbn:se:lnu:diva-85349OAI: oai:DiVA.org:lnu-85349DiVA, id: diva2:1324683
Educational program
Biology Programme, 180 credits
Supervisors
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Available from: 2019-06-19 Created: 2019-06-14 Last updated: 2019-06-19Bibliographically approved

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CiteExportLink to record
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