Morphological variability and age structure in a population of Bufo verrucosissimus (Anura: Bufonidae) from Artvin, Turkey

Abstract

We investigated morphological diversity (external body traits, coloration patterns and skin structure) and age structure in a population of Caucasian toad (Bufo verrucosissimus) from Lake Borçka Karagöl, situated in the vicinity of Artvin on the northeastern border of Turkey and Georgia. Age was determined using phalangeal skeletochronology. The external morphological variability was assessed using the linear measurement of 27 body-related characters and the photographs of each specimen. According to the results, the means of head length and head width were found significantly lower in Karagöl population as opposed to Caucasian populations, but average body size did not differ among all populations. Coloration and pattern features of the specimens from Karagöl were identical to those of Caucasia. Most of the females have brown tones and males are usually olive green and brown. The indiscrete elongated dark bands on parotoids did not extend behind the gland. PCA analysis confirmed a clear separation between the sexes and a high degree of female-biased sexual size dimorphism was determined based on the body size (SDI index: +0.41). The constructed Von Bertalanffy growth curve models yielded similar profiles in both sexes. Body size and age were significantly correlated in both models, but growth coefficient value was higher in males. Accordingly, the mean age of the Karagöl population is greater in both sexes, but the lifespan and maximum age are greater in Caucasus populations.