Observations on the larval development of some Malagasy frogs, with notes on their ecology and biology (Anura: Dyscophinae, Scaphiophryninae and Cophylinae)

In this paper, tadpoles belonging to three related groups of Malagasy frogs are described; both the Dyscophinae and the Cophylinae are subfamilies of the Microhylidae, while the Scaphiophryninae are alternatively assigned to this subfamily or to the Ranidae. The larvae were reared up to the juvenile stage in order to classify them. The tadpole of Dyscophus quinquelineatus (Dyscophinae), the first to be described within the genus, is of the microphagous microhylid type; it has a median spiracle, neither denticles nor beak or papillae, the nostrils do not appear until shortly before the metamorphosis, and the forelimbs develop behind the branchial chambers. The tadpole of Pseudohemisus granulosus (Scaphiophryninae), the first to be described within the genus with certainty, shows microhylid features, such as the absence of beak and denticles, the retarded appearance of the nostrils, and the development of the forelimbs behind the branchial chambers. However, the intermediate position of the spiracle, between median and sinistral, and the papillae around the mouth indicate affinities with other groups. The larval form of the Scaphiophryninae is just as difficult to classify as the adult. The systematic position of this subfamily is discussed and the assumption is made that it represents a relict of the ranoid stock from which the Microhylidae evolved. The larval development in the arboreal species Platyhyla grandis, Plethodontohyla notosticta and Anodonthyla boulengeri (Cophylinae) is similar. The large eggs are deposited separately in arboreal holes filled with water, mainly in the dry season. The larva hatches just before the limb buds occur; it has neither spiracle, nor anus, beak, denticles or papillae, and it is free-swimming. It completes its development on the large amount of yolk within the nesting site. It is demonstrated, that parental care occurs in this group. The male stayed with the developing spawn in all cases. Removal of the male caused a high mortality of the spawn, due to mould. The food items, recovered from species of Cophylinae, consisted mainly of ants.