Parâmetros reprodutivos de quelônios continentais brasileiros

Abstract

Among the 360 species of chelonians currently known, 38 occur in Brazil exhibiting variable reproductive strategies, highly influenced by morphological parameters and environmental aspects that exert a strong influence on the reproductive success of these animals. Despite the low diversity in view of other vertebrate groups, most data on the biology of chelonians come from a few species from restricted localities, such as of the Amazonian Podocnemid turtles. Aiming to throw further light on the reproduction of Brazilian chelonians, we gathered information from the literature on reproductive aspects of continental taxa searching for reproductive patterns and knowledge gaps. Exploring three main databases (i.e., Web of Science, Scielo, and Google Scholar) we detected some general tendencies that deserve notice. For instance, the most common spawning sites of the family Chelidae lie in forest formations (60%) and grasslands (27%), where nests are preferably deposited in sandy (57%) and clay soils (28%), often covered by a thick layer of leaf litter. Species of the family Podocnemididae prefer sandy formations of the riverbanks for nesting (50%), although some species show generalist tendencies (e.g., Podocnemis erythrocephala and Peltocephalus dumerilianus). With very few exceptions, sexual dimorphism of size (with females larger than males) represents a general tendency of continental Brazilian chelonians, while the only species lacking secondary sexual differences is Platemys platycephala. The environment greatly affects the reproduction of chelonians, a fact that may help explaining similar preferences (adaptive convergences) exhibited of syntopic distantly related taxa (e.g., Cerrado populations). In addition, environmental parameters also affect incubation time, embryo development, sex determination, and hatching success.