Ontogenetic color change in the tail of blue-tailed skinks (Plestodion elegans)

Abstract

Ontogenetic color change in animals is an interesting evolution-related phenomenon that has been studied by evolutionary biologists for decades. However, obtaining quantitative and continuous color measurements throughout the life cycle of animals is a challenge. To understand the rhythm of change in tail color and sexual dichromatism, we used a spectrometer to measure the tail color of blue-tailed skink (Plestiodon elegans) from birth to sexual maturity. Lab color space was selected due to its simplicity, fastness, and accuracy and depends on the visual sense of the observer for measuring the tail color of skinks. A strong relationship was observed between color indexes (values of L*, a*, b*) and growth time of skink. The luminance of tail color decreased from juveniles to adults in both sexes. Moreover, we observed differences in color rhythms between the sexes, which may be influenced by different behavioral strategies used by them. This study provides continuous measurements of change in tail color in skinks from juveniles to adults and offers insights into their sex-based differences. While this study does not provide direct evidence to explain the potential factors that drive dichromatism between the sexes of lizards, our finding could serve as a reference for future studies exploring possible mechanisms of ontogenetic color change in reptiles.

Keywords: Plestiodon elegans; chromatism; colour change; quantitatively measure; spectrometer.

FIGURE 1

Tail color change at different stages of male (a) and female (b) Plestiodon elegans. Numbers in the horizontal axis are weeks after birth.

FIGURE 2

Distributions of tail colors (L*a*b* values) for the Plestiodon elegans population at three age groups. (a) L* for male skink; (c) a* for male skink; (e) b* for male skink; (b) L* for female skink; (d) a* for female skink; (f) b* for female skink. Error bars are +SD. Different letters indicate statistically significantly different across age groups (GLM Repeated Measures, p < .05) according to Tukey's honestly significant difference tests.

FIGURE 3

Relationship between ages and tail color variables measured in two gender groups. Lines were fitted with generalized model. Male juvenile was <34 weeks (red color); sub‐adult male is from 35 to 65 weeks (green color); adult male is more than 66 weeks (blue color). Female juvenile was <28 weeks; sub‐adult female is from 28 to 57 weeks; adult female is more than 57 weeks. Break period is from 37 to 48 weeks (hibernation).