Cytogenetics of Bolivian Endemic Red Howler Monkeys (Alouatta seniculus sara): Accessory chromosomes and Y-autosome translocation related numerical variations

Abstract

A karyotypic study on red howler monkeys, Alouatta seniculus sara, captured in Santa Cruz, Bolivia was carried out. The range of chromosome number was 2n = 48 to 51. Female had 9 pairs bi-arm chromosomes (including the submetacentric X-chromosome), male, however, had 7 pairs and two unpaied bi-arm chromosomes. The number of acrocentric chromosome (excluding the two smallest pairs, B1 and B2, because of their numerical variability) was 26 in female and 27 in male. A different chromosome number was frequently observed among cells even in a same individual. AG-band karyotype reveals a male specific acrocentric chromosome can be derived from the normal 6th chromosome by centromeric fission and insertion of an additional segment (probably Y-chromosome) between the telomeric end of two arms. The mnuerical range of B1 was 2 to 4 and that of B2 was 2 to 6 and that of B1十B2was 5 to 8. The B2 chromosome is numerically more variable than the B1, and male has more B1 chromosome (2.88) than female (2.13). Probably the facts, B2 is Cband negative and B1is centromeric C-band positive, m ight affect chromosome movement at meiotic and mitotic division The karyotype of Bolivian monkeys so far studied was highly endemic. The distribution of endemic species overlapped a paleoecological forest refuge of this region suggested by Brown (1982).