Karyotypes of eight species of Leptodactylus (Anura, Leptodactylidae) with a description of a new karyotype for the genus

Abstract

Karyotypes of eight species of Leptodactylus (Anura, Leptodactylidae) with a description of a new karyotype for the genus. Eight species of the Neotropical genus Leptodactylus were karyologically studied: seven of them (L. gracilis, L. mystacinus, L. petersii, L. pustulatus, L. macrosternum, L. ocellatus, L. labyrinthicus) presented 2n=22 and L. silvanimbus showed a distinctive karyotype with 2n=24. Nucleolar organizer regions (Ag-NORs) were detected in two different pairs of chromosomes: pair 4 at the proximal region of the long arm of one individual of L. mystacinus from Sao Paulo state and of L. petersii; and pair 8 of all other species (located terminally at the short arm of L. silvanimbus, L. ocellatus, L. macrosternum, L. pustulatus, and L. labyrinthicus; interstitially at the short arm in L. gracilis; and at the long arm in L. mystacinus from Mato Grosso state). The diploid number reported here for L. silvanimbus shared with Scythrophrys and Paratelmatobius could represent the an- cestral chromosome number for Leptodactylus (sensu Frost et al. 2006); in this case the 2n=22 karyotypes would then represent the derivative condition for the genus. Nevertheless, the distinctive karyotype of L. silvanimbus lead us to preclude a final decision on its relationships. Additional studies including morphological and molecular approaches are needed in order to clarify the phylogenetic position of L. silvanimbus.