Post-metamorphic growth, sexual maturation and body size dimorphism in the skipper frog, Euphlyctis cyanophlyctis (Schneider)

Abstract

Post-metamorphic growth to sexual maturity was studied in a tropical frog Euphlyctis cyanophlyctis that breeds all the year round, in large outdoor terraria. Sexual size dimorphism (SSD) was studied in both a natural population and those reared in outdoor terraria. The growth rate was high in the first 2-3 months in both sexes, but subsequently declined, reaching a plateau following sexual maturation. The growth rate was high during summer and low during winter, and its pattern paralleled the changes in the ambient temperature. The males matured between 3-6 months depending upon their growth rates; at this stage they developed vocal sacs and spermatozoa and engaged in calling. The females matured between 8-11 months of age and responded to injections of progesterone by producing mature eggs. Fecundity was positively correlated to snout-vent length (SVL)/body mass. The males and females attained maturity when they reached a critical minimum SVL of ∼42 mm and ∼55 mm respectively. Mean adult body size (SVL and body mass) of females collected from nature was 67.0±0.85 mm and 32.8±1.56 g, and that of males was 48.0±0.37 mm and 10.1±0.31 g. Male to female size ratio (F/M) was 1.4 indicating SSD and a larger female size. In laboratory-reared specimens also, SSD was obvious at sexual maturity. A larger body size in females is due to delayed sexual maturity relative to the males. These findings suggest that in E. cyanophlyctis SSD is manifested primarily due to differences in the age at sexual maturity rather than an inherent difference in the postmetamorphic growth rate between the sexes.