Razão sexual de podocnemis unifilis no Parque Indígena do Xingu, Mato Grosso, Brasil

Abstract

Temperature-dependent sex determination is one of the most important aspects of turtle reproductive biology. The incubation environment is a limiting factor for reproduction, because environmental characteristics are responsible for the temperature in the interior of the nest and consequently for the sex ratio of the hatchlings. To understand the influence of the characteristics of the physical environment on embryo development is still a challenge, because the wide range of variables involved makes it difficult to interpret results obtained in natural conditions. Aiming to fill the gaps in understanding the role of temperature in the differentiation of male and female Podocnemis unifilis, the temperature of 120 natural nests was monitored, concomitantly with incubation of eggs under controlled temperatures in the laboratory. Based on the sexes of hatchlings incubated in the laboratory, it was possible to establish the pivotal temperature. Then, the sex ratio of clutches in natural nests located on the beaches of the Xingu River, in the Xingu Indigenous Park (MT), was estimated. According to the constant-temperature equivalent, the sex ratio of hatchlings in the 2010 nesting season was 47% females. Nest placement is important for hatching success, principally for nests subject to flooding; but did not affect the nest temperatures. The management protocol adopted by the indigenous community and which involves the transfer of nests that are subject to flooding and to predation, did not affect the hatching success or nest temperatures, showing that it is the most appropriate method.