How reef fish see their colourful world: why UV-and red vision are important for damselfish (Pomacentridae)
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1
Centre of Ecology, Evolution and Biogeochemistry, Swiss Federal Institute of Aquatic Science and Technology, Switzerland
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2
Institute of Ecology and Evolution, Department of Biology, Faculty of Science, University of Bern, Switzerland
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3
Queensland Brain Institute, University of Queensland, Australia
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4
Department of Biology, University of Maryland, United States
Coral reef fish not only live in one of the world’s most colourful and diverse ecosystems, they are themselves most variable in terms of colouration and ecologies, and thus form a promising system to study the role of visual communication. Damselfishes (Pomacentridae) are particularly well-suited to understand the mechanisms underlying visual system adaptation. With more than 390 species, they are an abundant, colourful, and diverse coral reef fish family possessing one of the widest ranges of spectral sensitivities of any fish families from UV to long-wavelengths.
Making use of modern molecular approaches, we study visual adaptation at the level of photoreceptors and their intrinsic light absorbing visual pigment genes (opsins) by comparing various damselfish species, and comparing these with reef fish from other families:
• We compare sequence and expression variation in opsins by using Illumina RNA sequencing.
• We then use the variation in visual sensitivities among species (opsin setup) to make predictions for adaptation in visually relevant tasks.
Reef fish have one rhodopsin (RH1) used for scotopic, and a varying number of cone opsins used for photopic vision with sensitivity to short (SWS1, SWS2B, and SWS2A), medium (RH2A and RH2B) and long (LWS) wavelengths. While the medium sensitive opsins are well matched to ambient light conditions present on reefs, we highlight that sensitivities on either end of the spectrum seem to have adapted to specific visual tasks, namely social signaling and feeding strategy.
Interestingly, among a number of reef fish families investigated so far, all damselfish species express the UV-sensitive SWS1 opsin, whereas other families only have very few or no species expressing it. Moreover, we found that the UV opsin gene has duplicated within the damselfish phylogeny with species expressing one or the other or even both copies. Sequence divergence between the UV opsin copies indicates a 10nm shift of spectral sensitivity and provides a fine-scale tuning mechanism in the UV range. This, together with the fact that most damselfish have UV-reflective body parts, supports the existing hypothesis they might benefit from a close-range UV-based private communication channel hidden from UV-blind predators.
Based on a previous study (Stieb et al., 2017) in damselfishes demonstrating a link between increased LWS-expression and herbivory, possibly enhancing the ability to detect algae that reflect in longer wavelengths, we find that the association between LWS upregulation and herbivory is also present in other reef fish families, independently evolved in blennies, angel-, butterfly-, and surgeonfishes. We further found a strong link of increased LWS expression in damselfish species that reflect in the longer wavelengths (orange to red). We propose that sensory drive might have triggered the evolution of red communication signals, possibly as a by-product of an adaptation to a feeding strategy. Current work in progress is aiming to test this hypothesis.
References
- Stieb SM, Cortesi F, Sueess L, Carleton KL, Salzberger W, Marshall NJ. 2017. Why UV- and red-vision are important for damselfish (Pomacentridae): Structural and expression variation in opsin genes. Mol. Ecol. 26(5):1323-1342. doi: 10.1111/mec.13968.
Keywords:
reef fish,
Opsin gene expression,
opsin duplication,
visual communication,
Feeding strategies
Conference:
XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019.
Presentation Type:
Poster
Topic:
EVOLUTIONARY GENOMICS OF FISHES
Citation:
Stieb
SM,
Cortesi
F,
Carleton
K,
Mitchell
L,
Seehausen
O and
Marshall
J
(2019). How reef fish see their colourful world: why UV-and red vision are important for damselfish (Pomacentridae).
Front. Mar. Sci.
Conference Abstract:
XVI European Congress of Ichthyology.
doi: 10.3389/conf.fmars.2019.07.00048
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Received:
24 May 2019;
Published Online:
14 Aug 2019.
*
Correspondence:
Dr. Sara M Stieb, Centre of Ecology, Evolution and Biogeochemistry, Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, 6047, Switzerland, sara.stieb@eawag.ch