Light‐Induced Pigment Aggregation in Xanthophores of the Medaka, Oryzias latipes

Abstract

The response mechanism of medaka xanthophores to light was examined at the cellular level. Innervated and denervated xanthophores of adult medakas responded to light (9,000 lux) within 30 sec by pigment aggregation, and this aggregation was not mediated through alpha-adrenoceptors on the cell membrane. Maximum sensitivity to light was at wavelengths of 410-420 nm, and the direct effect of light was reversible. Xanthophore responsiveness to light in summer was higher than that in winter. Ca2+ and calmodulin were not involved in the response, but rather, an important role for cAMP and phosphodiesterase (PDE) was suggested. It seems likely that photoreception by visual pigment which is sensitive to light at wavelengths of 410-420 nm increases PDE activity, probably via a G-protein, such as occurs with visual cells in the retina, which causes a decrease in levels of cytosolic cAMP, in turn leading to pigment aggregation within medaka xanthophores.

Possible Involvement of Cone Opsins in Distinct Photoresponses of Intrinsically Photosensitive Dermal Chromatophores in Tilapia Oreochromis niloticus

“…retrograde vs. anterograde) is not identical in the same chromatophore class. For instance, xanthophores under illumination disperse in Trematomus bernacchii , but aggregate in Oryzias latipes [38], [39].…”

Direct Reception of Light by Chromatophores of Lower Vertebrates

“…We have not yet confirmed the presence of a 400-nm-sensitive photopigment in tilapia erythrophores. In many chromatophore species, light with wavelengths between 400 and 420 nm has been reported to be effective in inducing a direct photoresponse (Table 1): 400-420 nm for cultured melanophores derived from young or larval platyfish (33), 420 nm for Rhodeus melanophores from larval forms (35), 410-420 nm for medaka xanthophores (40), and 415 nm for cultured melanophores from the medaka (42). Therefore, we should be able to identify violet-sensitive opsin-like pigments responsible for photoresponses of such chromatophores in the future.…”

Functional characterisation of the chromatically antagonistic photosensitive mechanism of erythrophores in the tilapiaOreochromis niloticus

“…In addition to neural and hormonal regulation, chromatophores can respond directly to light and thus they are categorised as non-visual photoreceptors. Their ability to respond to incident light varies in a species-specific manner and also depends on developmental stage (Naora et al, 1988;Moriya et al, 1996;Oshima et al, 1998;Chen et al, 2014). Like other photoreceptors, chromatophore photosensitivity is proposed to be associated with the expression of opsin-based photopigments within cells (Ban et al, 2005).…”