Energy allocation patterns inBufo marinusfrom two habitats in Venezuela

Abstract

ABSTRACTPatterns of energy allocation in the cane toad,Bufo marinus, were explored by analysing the seasonal variations in fat bodies and gonads in two populations subjected to different rainfall regimes and water permanency. In both populations, fat deposition occurred shortly after the rainy season due to an increase in feeding activity. In contrast, the timing of reproduction varied between sites according to the availability of suitable water bodies. Nevertheless, females with mature oocytes were predominant during the dry season, even in populations that bred throughout the year in permanent ponds. This suggests that seasonal variations in the nutritional condition of adults may also result in a tendency towards cyclicity in the reproduction ofB. marinusin tropical regions. Analyses of allometric relationships of reproductive and storage tissues with body weights indicated that the fractions of weights in reproductive tissues did not vary either with the size of females or between populations. On the contrary, not only did larger toads have proportionally larger fat bodies, but those from wet sites had greater fractions of weight allocated to fat bodies than those from dry sites. This suggests that reproductive output may be fixed in this species and, therefore, excess energy is allocated to fat bodies. Given that the initiation of ovarian cycles depends on the restoration of proper nutritional levels, energy stored in fat bodies during breeding may allow females to resume a new ovarian cycle shortly after spawning and thus maximize the number of reproductive events.