Plastral Colour Fading of Pseudemys concinna Leconte 1830 (Testudines: Emydidae)

Abstract

Geometric techniques can be easily applied to many zoological problems, from recognizing subpopulations to studying sexual dimorphism. Pseudemys concinna (P. concinna) is a large terrapin species known as the Eastern River Cooter, native to North America. The hypothesis was to test if plastral pattern tends to fade with age. The present study applies geometric techniques to assess size in a sample of 20 fresh corpses of P. concinna (18 females and 2 males). Plastron color (red, blue, and green channels) was used to objectivize this fading pattern. A negative regression between size and color was registered, so the colour plastral intensity of P. concinna LeConte 1830 tends, effectively, to fade with age. Elucidating the cellular and chemical mediators and mechanisms of these slow color changes will likely require laboratory study.