Filling knowledge gaps about the ‘Data Deficient’ species Zachaenus carvalhoi Izecksohn, 1983 (Anura, Cycloramphidae): an endemic frog from the Atlantic Forest of southeastern Brazil

Zachaenus carvalhoi is an endemic frog from the Atlantic Forest of southeastern Brazil. It is considered a rare species, being currently classified as ‘Data Deficient’ by the IUCN due to the shortage of information about its natural history, ecological requirements, distribution and population trends. In the present study, we aim to fill gaps in the current knowledge of this species by: updating its altitudinal distribution range; describing its release call; providing new natural history data; and describing its karyotype. During fieldwork in the Municipality of Cataguases, Minas Gerais State, we recorded individuals of Z. carvalhoi in three small forest fragments, one of them at only 230 m a.s.l., which now represents the lowest known altitudinal record for this species. In all occasions, we only recorded this frog in calling activity during rainy days, suggesting an opportunistic breeding strategy. Moreover, the karyotype of Z. carvalhoi (2n = 26) is similar to those of other species of the family Cycloramphidae, but it differs remarkably in morphology and fundamental number. The advertisement call presented differences in the spectral structure in comparison to descriptions from other populations. In conclusion, Z. carvalhoi seems to be an explosive breeder occurring along a wide altitudinal range (low- and highland Atlantic Forest), and physical barriers such as mountain chains may not be a constraint to its dispersal. Furthermore, this species represents a promising subject for investigations over both bioacoustics and cytogenetic studies.