Frogs in the genus Gephyromantis from Madagascar were assumed to have a direct developmental mode, i.e. the complete embryonic and larval development within the egg, but recently free-swimming, exotrophic tadpoles of a few species have been found. Herein we provide detailed morphological descriptions of the tadpoles of five more species of this genus, indicating a developmental mode other than direct development in species of Gephyromantis. Tadpoles of Gephyromantis granulatus, G. sculpturatus, G. tschenki, and G. ventrimaculatus were found free-swimming in streams, and tadpoles of G. sp. aff. blanci were raised after hatching from clutches found in the leaf litter. All tadpoles were identified by DNA barcoding. The oral discs of all five species are characterized by the lack of many typical morphological traits of exotrophic tadpoles (such as oral papillae and keratodonts). This indicates that these tadpoles are either non-feeding (endotrophic) or only facultatively feeding tadpoles. We classify these tadpoles as nidicolous based on the observation that the larvae of G. sp. aff. blanci stayed after hatching in the jelly nest until metamorphosis. It remains unclarified whether all species have strictly nidicolous tadpoles, and the larvae of the four species found in the streams were just accidentally washed into these streams; alternatively, some of these tadpoles might be nidicolous at first but in some species need to live in free water at later stages.

Acoustic communication is widespread among adult stages of terrestrial animals and fish and has also been observed in insect larvae. We report underwater acoustic communication in the larvae of a frog, Gephyromantis azzurrae, from Isalo, a sandstone massif in western Madagascar. According to our field data, these tadpoles live in streams and prefer habitats characterized by comparatively low temperatures, shallow water depth, and a relatively fast current. Feeding experiments indicated that the tadpoles are carnivorous and macrophagous. They consumed insect larvae and, to a lesser extent, small shrimps, and conspecific as well as heterospecific tadpoles. Calls of these tadpoles consisted either of single click notes or of irregular series of various clicks. Some complex calls have a pulsed structure with three to nine indistinct energy pulses. Production of the pulses coincided with rapid closure of the jaw sheaths and often with an upward movement of the body. Calls were emitted while attacking prey and occurred significantly more often when attacking conspecifics. Tadpoles that had not been fed for some time emitted sounds more frequently than those that had been regularly fed. The spectral frequency of the calls differed in tadpole groups of different size and was higher in groups of smaller tadpoles, suggesting that spectral frequency carries some information about tadpole size which might be important during competitive feeding to assess size and strength of competitors. This report differs from those for the larvae of South American horned frogs, Ceratophrys ornata. These are the only other tadpoles for which sound production has reliably been reported but the calls of Ceratophrys tadpoles occur mainly in a defensive context.

We provide morphological descriptions of the tadpoles of ten species of Malagasy treefrogs of the genus Boophis (family Mantellidae). Based on individuals determined by DNA barcoding, the larvae of eight species are described for the first time: B. anjanaharibeensis, B. axelmeyeri, B. elenae, B. englaenderi, B. luciae, B. rhodoscelis, B. roseipalmatus, and B. vittatus. For two additional species, B. andreonei and B. microtympanum, we provide descriptions from other localities than the previously known larvae. All tadpoles described herein are stream-adapted, exotrophic, and of a relatively generalized morphology. In general, we found a morphological similarity of larvae belonging to phenetic species groups of Boophis, but more detailed analyses showed several differences between taxa that are known to be sister species or closely related to each other: B. luciae has a much higher number of oral papillae than B. sibilans, B. roseipalmatus has a slightly lower number of papillae and possibly a stronger caudal musculature than B. madagascariensis, and B. elenae has a distinctly lower number of oral papillae and keratodonts in the first upper keratodont row than B. sandrae. This indicates that tadpole characters might, in some cases, provide good taxonomic characters in Boophis, a genus in which adults of closely related species are often morphologically extremely similar.