Reproductive aspects of a population of Physalaemus gracilis (BOULENGER 1883) (Anura: Leptodactylidae) from south Brazil

Abstract

We investigated the reproductive biology of Physalaemus gracilis in a population from the state of Rio Grande do Sul (Brazil), and collected a total of 871 individuals through pitfall traps from May 2001 to January 2003. The largest collection of individuals occurred during the autumn and winter months, in July 2001 and from May to August 2002. The occurrence of individuals caught in pitfall traps was positively related to the temperature. The data about snout-vent length changed throughout the seasons, decreasing in spring and summer, possibly due to the recruitment of juvenile individuals. This population presented a seasonal reproductive activity and sexual dimorphism, characterized by higher values of snout-vent length and weight in females in comparison to males. The reproductive investment of the studied population supports the idea that larger females invest proportionally more in their offspring. The gradual increase of female gonadosomatic index, which coincided with the largest amount of mature oocytes, may indicate that females were prepared to oviposition process that would probably occur in spring. In contrast, males may have a continuous readiness to mate throughout the year.

Keywords: amphibians, gonadosomatic index, reproductive investment, seasonality.