First Report of B Chromosomes in Caecilians (Amphibia: Gymnophiona)

Abstract

Gymnophion amphibians (caecilians) are less well studied than the other two orders of extant amphibians: Anura and Caudata. We describe the first recorded presence of supernumerary (B) chromosomes in the order Gymnophiona, where a lone intensely stained B chromosome was observed in the somatic metaphase and meiotic complements of the Indian ichthyophiid, Uraeotyphlus gansi. Given the rarity of B chromosomes in caecilians and their sporadic presence within U. gansi, it is likely that these represent aneuploidy and are a recent acquisition derived from centromeric drive.