Karyological Evidence for a Cryptic Species of Piranha within Serrasalmus rhombeus (Characidae, Serrasalminae) in the Amazon
Cytogenetic data obtained for Serrasalmus rhombeus revealed two cytotypes (cytotype 1 and cytotype 2) at four sampling sites. Cytotype 1 consists of 2n = 60, 20M + 24SM + 6ST + 10A and was detected in specimens from Negro River (Anavilhanas Islands), Solimões River (Camaleão Lake), confluence of Negro and Solimões Rivers (Catalão Lake), and Uatumã River. Cytotype 2 consists of 2n = 58, 22M + 24SM + 2ST+10A and was detected in specimens from Catalão and Camaleão Lakes. In Cytotype 2, the first chromosome pair was almost twice the size of second pair, and the constitutive heterochromatin pattern of each cytotype is distinct. The two cytotypes occurred sympatrically at Catalão and Camaleão Lakes, and no intermediates between the cytotypes were detected, suggesting each cytotype represents a different fish species.Abstract
Geographical distribution of distinct cytotypes found in nominal forms of Serrasalmus rhombeus. White squares represent collection localities for cytotype 1 (2n = 60), and black squares are localities for cytotype 2 (2n = 58)
Giemsa (A), NOR (B) and C-Band (C) karyotypes of Serrasalmus rhombeus cytotype1
Giemsa (A), NOR (B) and C-Band (C) karyotypes of Serrasalmus rhombeus cytotype 2