Sex chromosomes in the Vizcacheras' White-lipped frog, Leptodactylus bufonius (Anura, Leptodactylidae).

Rosio G Schneider,Juan M Boeris,Ivana N Reinko,Darío E Cardozo,Juan M Ferro,Diego Baldo

doi:10.1590/0001-3765202120190426

Abstract

Cytogenetic analyses were performed on specimens of Leptodactylus bufonius from different localities in Argentina. Mitotic chromosomes were studied with Giemsa and differential staining techniques (Ag-NOR, C-banding, and CMA3/DAPI) and fluorescence in situ hybridization with the 18S DNAr probe. All specimens showed karyotypes with 2n = 2x = 22 and FN = 44. Secondary constrictions were present in the long arm of chromosome pair 8, coincident with Ag-NOR and hybridization signals of the 18S DNAr probe. The C-banding technique evidenced an important amount of heterochromatin with a sex-linked pericentromeric band in the short arm of chromosome pair 4. This heterochromatic band was heteromorphic in males but present in both homologues of females, and it was CMA3 positive (DAPI negative) at fluorescence staining. The occurrence of heteromorphic XY sex chromosomes in L. bufonius is the second known case in Leptodactylus and the fifth within the speciose family Leptodactylidae.

Highlights

The diverse and complex ways of sex determination among different vertebrate taxa constitute an interesting research field that is currently focused on revealing genes and mechanisms involved, as well as chromosome locations (Bull 1983, Valenzuela 2008)
We describe a new case of heteromorphic sex chromosomes in Anura, which constitutes the second known in the genus Leptodactylus
The nucleolar organizer regions (NORs) were detected by Ag-NOR staining according to Howell & Black (1980) and by fluorescent in situ hybridization (FISH) with the ribosomal 18S biotinylated probe (Pinkel et al 1986)

Summary

Introduction

The diverse and complex ways of sex determination among different vertebrate taxa constitute an interesting research field that is currently focused on revealing genes and mechanisms involved, as well as chromosome locations (Bull 1983, Valenzuela 2008). To date, this is a poorly studied topic in Anura, and those species with already identified sex chromosomes are just a small proportion as compared with other vertebrate orders (Miura 2017).

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Conclusion