Hormonal regulation of colour change in eyes of a cryptic fish.

Helen Nilsson Sköld,Daniel Yngsell,Muhmd Mubashishir,Margareta Wallin

doi:10.1242/bio.20149993

Helen Nilsson Sköld, Daniel Yngsell + Show 2 more

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https://doi.org/10.1242/bio.20149993

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Journal: Biology open	Publication Date: Jan 16, 2015
Citations: 33	License type: CC BY 3.0

Affiliation: University of Gothenburg, Kristianstad University

Abstract

ABSTRACTColour change of the skin in lower vertebrates such as fish has been a subject of great scientific and public interest. However, colour change also takes place in eyes of fish and while an increasing amount of data indicates its importance in behaviour, very little is known about its regulation. Here, we report that both eye and skin coloration change in response to white to black background adaptation in live sand goby Pomatoschistus minutes, a bentic marine fish. Through in vitro experiments, we show that noradrenaline and melanocyte concentrating hormone (MCH) treatments cause aggregation of pigment organelles in the eye chromatophores. Daylight had no aggregating effect. Combining forskolin to elevate intracellular cyclic adenosine monophosphate (cAMP) with MCH resulted in complete pigment dispersal and darkening of the eyes, whereas combining prolactin, adrenocorticotrophic hormone (ACTH) or melanocyte stimulating hormone (α-MSH) with MCH resulted in more yellow and red eyes. ACTH and MSH also induced dispersal in the melanophores, resulting in overall darker eyes.By comparing analysis of eyes, skin and peritoneum, we conclude that the regulation pattern is similar between these different tissues in this species which is relevant for the cryptic life strategy of this species. With the exception of ACTH which resulted in most prominent melanophore pigment dispersal in the eyes, all other treatments provided similar results between tissue types. To our knowledge, this is the first study that has directly analysed hormonal regulation of physiological colour change in eyes of fish.

Highlights

An increasing amount of studies report that the eyes of animals are important for vision, and that the eye colour is involved in signalling and communication
The rest of the eye is spherical in shape and the iridophores dominate at the back of the eye, chromatophores of different pigment types are frequent, especially at the dorsal side which is visible in situ to the observer (Fig. 1D)
Factors causing paling of eyes, peritoneum and skin Both melanocyte concentrating hormone (MCH) and noradrenaline (NA) caused a rapid and persistent paling effect caused by pigment aggregation in melanophores and erythrophores of eyes, peritoneum and skin (Table 1; Fig. 3A,B)

Summary

Introduction

An increasing amount of studies report that the eyes of animals are important for vision, and that the eye colour is involved in signalling and communication. The authors found that the eye colour changed from brown to redbrown with age and that younger males had more red eyes than females. They reported that birds exposed to polycarbonated bromide showed less colourful eyes and reduced reproductive success. After transfer to dark background, the same individuals showed darkening of the skin and eyes (Fig. 2C,D). Factors causing paling of eyes, peritoneum and skin Both melanocyte concentrating hormone (MCH) and noradrenaline (NA) caused a rapid and persistent paling effect caused by pigment aggregation in melanophores and erythrophores of eyes, peritoneum and skin (Table 1; Fig. 3A,B). MCH (Sigma Aldrich) was stored at 220 ̊C as 10 mM stock solution and used at 100 nM.

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Conclusion