Pigment cell mechanisms underlying dorsal color-pattern polymorphism in the japanese four-lined snake

Abstract

To provide histological foundation for studying the genetic mechanisms of color-pattern polymorphisms, we examined light reflectance profiles and cellular architectures of pigment cells that produced striped, nonstriped, and melanistic color patterns in the snake Elaphe quadrivirgata. Both, striped and nonstriped morphs, possessed the same set of epidermal melanophores and three types of dermal pigment cells (yellow xanthophores, iridescent iridophores, and black melanophores), but spatial variations in the densities of epidermal and dermal melanophores produced individual variations in stripe vividness. The densities of epidermal and dermal melanophores were two or three times higher in the dark-brown-stripe region than in the yellow background in the striped morph. However, the densities of epidermal and dermal melanophores between the striped and background regions were similar in the nonstriped morph. The melanistic morph had only epidermal and dermal melanophores and neither xanthophores nor iridophores were detected. Ghost stripes in the shed skin of some melanistic morphs suggested that stripe pattern formation and melanism were controlled independently. We proposed complete- and incomplete-dominance heredity models for the stripe-melanistic variation and striped, pale-striped, and nonstriped polymorphisms, respectively, according to the differences in pigment-cell composition and its spatial architecture.

Pigment cell mechanism of postembryonic stripe pattern formation in the Japanese four‐lined snake

“…To characterize the pigment cell mechanisms of ontogenetic color pattern formation, we compared the number of epidermal melanophores, the proportion of dermal melanophores, and the vertical architecture of dermal pigment cells between juveniles (estimated in this study) and adult snakes (Kuriyama et al, ). In both the striped and nonstriped morphs, the number of epidermal melanophores and the proportion of dermal melanophores were higher in adult snakes than in juvenile snakes at the Nos.…”

“…Kuriyama et al () concluded that changes in the densities of epidermal and dermal melanophores explain the observed variation in stripe vividness between the striped and nonstriped morphs. Our results were consistent with this inference and with the results of Murakami et al (); spatial variation in the abundance and architecture of epidermal and dermal melanophores is the key pigment‐cell mechanism that explains variation in stripe vividness.…”

“…The pigmentation mechanisms that determine the color pattern polymorphism of the Japanese four‐lined snake Elaphe quadrivirgata are well‐examined (Kuriyama et al, ). Populations of E. quadrivirgata exhibit a pronounced color polymorphism, including striped, pale‐striped, nonstriped, banded, and melanistic morphs (Mori et al, ; Tanaka and Mori, , Kuriyama et al, ). In a histological study of the pigment cells of the striped, nonstriped, and melanistic morphs of adult E .…”

“…In a histological study of the pigment cells of the striped, nonstriped, and melanistic morphs of adult E . quadrivirgata , Kuriyama et al () revealed that spatial variation in the abundance and architecture of epidermal and dermal melanophores is a key determinant of differences in stripe vividness between striped and nonstriped phenotypes. Murakami et al () showed that the stripes of juvenile E. quadrivirgata are reddish, but eventually become dark brown in adults.…”

Developmental mechanisms of longitudinal stripes in the Japanese four‐lined snake

“…The Japanese four‐lined snake Elaphe quadrivirgata has a naturally occurring body color polymorphism, including striped, pale‐striped, nonstriped, banded, and melanistic morphs (Mori, Tanaka, Moriguchi, & Hasegawa, ). Vivid striped and nonstriped morphs possess the same set of epidermal melanophores and dermal pigment cells (xanthophores at top, iridophores in middle, and melanophores in bottom), but vertical stratification of dermal pigment cells differs in different colored scales and the degree of spatial aggregation and concentrations of epidermal and dermal melanophores are the key determinants of stripe vividness in terms of sharpness of the boundary between dark‐ and light‐colored scales (Kuriyama et al, ). Even at the hatching, stripe and nonstripe patterns are detectable.…”