Egg numbers and fecundity traits in nine species of <i>Mantella</i> poison frogs from arid grasslands and rainforests of Madagascar (Anura: Mantellidae)

Abstract

The body size and number of eggs in dissected females were
analysed in nine species of the Malagasy frog genus Mantella
basing upon preserved specimens. These species were distinguished in terms of habitat and grouped as ‘grassland
species’ (included M. betsileo, M. expectata, M. viridis), and ‘rainforest species’ (M. baroni, M. crocea, M. cowani, M. laevigata, M. nigricans, M. pulchra). The species with the lowest egg - number was M. cowani with a mean egg number of 37 ± 15, while the species with the highest egg-number was M. viridis with 115 ± 21 eggs. In general, the grassland species are characterised by a higher number of relatively small eggs. Moreover, their fecundity was positively and significantly correlated to female body size. Rainforest species were smaller in size and with a lower number of eggs. We interpreted these differences as possible consequences of habitat adaptations. Among the studied species, the Critically Endangered Mantella cowani is also featured by a low number and large size of eggs. This is likely correlated with the high elevation site of the central highlands where this species occurs.