The Tadpole of Chiasmocleis altomontana (Anura: Microhylidae)

Background. Describing the morphology of anuran larvae contributes towards filling gaps in taxonomy and natural history. This is especially relevant for explosive breeders, in which adults remain at the reproduction site for only a short period, while tadpoles may be more conspicuous. Here, we describe the larval external morphology and internal oral anatomy of the microhylid frog Chiasmocleisaltomontana from near the type locality in southeastern Brazil.

Methods. We took 13 morphometric measurements of 11 tadpoles between stages 35 and 39 from four ponds. To compare the larval external morphology of the genus, we also built a morphospace using measurements provided by the original descriptions. To impute missing data, we used a traits imputation method that considered the phylogenetic relationships of the species.

Results. The tadpole of C. altomontana is the largest among the Atlantic Forest species and the second largest of the genus, after C. anatipes. Like all species of the genus, the larva of C. altomontana is exotrophic, suspension feeder, Orton type II, and occurs in lentic temporary environments. Overall, C. altomontana shows subtle differences in dorsal fin height, dorsal fin insertion, tip of the tail, and snout in lateral view from its congeners. Chiasmocleis altomontana differs greatly in terms of shape from the remaining species of the genus, especially from its sister species C.mantiqueira and others from the Atlantic Forest clade. However, the overall pattern suggests an evolutionaryconvergence in the tadpole shape, since species from distant clades were positioned at the centre of the morphospace.