Evaluation of the effectiveness of cryptic coloration of the Carolina anole’s skin

A B Kiladze

doi:10.15421/021950

Abstract

Cryptic coloration of animals’ integument is one of the effective adaptations that allow them to lead an active lifestyle while being protected from natural enemies due to visual disguise. This is achieved by the similarity of body color of a particular individual to the background of various substrates in its environment. The morphological and functional basis of cryptic coloration in vertebrates, including reptiles, is ensured by the skin pigmentation. Using bioinformatic methods, we calculated the skin camouflage index of the Carolina anole (Anolis carolinensis Voigt, 1832) in various conditions of its habitat. The skin camouflage index (Ic) is the ratio of the sum of the average values of rgb coordinates of the skin color to the sum of the average values of rgb coordinates of the color of the external substrate. Ic satisfies the effective level of adaptation to habitat conditions if it falls within the range of 0.80–1.20. It has been shown that rgb-values of the dominant color of the dorsal skin of green anoles slightly differ from the similar parameters characteristic of the deciduous habitat, which is reflected by Ic of its skin (0.94). In the brown anoles on a background of woody substrate, the Ic value of its skin (0.88) is also optimal, since it exceeds the lower limit (0.80), which indicates close values of the sums of the rgb coordinates of the skin color and the color of the external background. In the mixed green-brown anoles, the deciduous habitat is preferable to the woody one. In the first case, Ic (1.11) is in the optimum zone, and in the second case, Ic (0.70) goes beyond the lower limit of the optimum, which indicates a greater vulnerability of the animal to external threats. We have confirmed the relativity of visual hiding of the skin that is effective only in the habitat conditions in which the camouflage abilities of the skin manifest as fully as possible.

Highlights

Adaptation of animals is an important factor in the success of life strategies in specific habitat conditions, which, according to the Charles Darwin’s (1809−1882) theory, is the result of evolutionary transformations (Gardner, 2009)
Biological adaptations are relative in their nature, which determines the preservation of life only for those animals that are the most adapted to a particular system of environmental factors (Ghiselin, 1966; Vitt, 1981)
We have studied seven adult animals of the Carolina anole Anolis carolinensis Voigt, 1832 (Squamata: Dactyloidae): animals of both sexes of three color forms kept in the scientific terrarium of the Zoological Museum of Lomonosov Moscow State University (Moscow, Russia) and in the terrarium of the Oceanarium of Antalya (Turkey)

Summary

Introduction

Adaptation of animals is an important factor in the success of life strategies in specific habitat conditions, which, according to the Charles Darwin’s (1809−1882) theory, is the result of evolutionary transformations (Gardner, 2009). As an example of effective adaptation to a particular habitat, allows many animals, on the one hand, to ensure opportunities for hunting potential prey, and, on the other hand, to protect themselves from predators (Stevens & Merilaita, 2009, 2011). In both cases, masking the skin according to the environment, which is an example of passive protection, is the necessary condition for successful vital activity (Norris, 1967; Talbot, 1977; Henry et al, 2008). The issue of cryptic coloration in animals has been reviewed the most completely in the fundamental monograph by Hugh Cott (1900−1987) “Adaptive coloration in animals” (Cott, 1940)

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