Mitotic and meiotic analysis in Arctocephalus australis (Otariidae)

The karyotype with C-, G- and NOR-banding of Arctocephalus australis is rep orted for the first time. The chromosomal number is 2n = 36. The X chromoso me, identified in G-banded metaphases from males, is metacentric and the Y chromosome is a minute chromosome, also metacentric. Pachytene spermatocyte s were used for synaptonemal complexes analysis with a surface spreading te chnique. A total of 17 autosomal synaptonemal complexes are observed plus t he XY pair. During early pachytene, the X and Y axes are thickened and rema in unpaired. As pachytene advances, a short SC is formed between the gonoso mes, as it is common among eutherian mammals. The particular asymmetrical a ppearance of the synaptonemal complex in the sex pair is described and comp ared to other cases among mammals.