Karyotypical description of Spheniscus magellanicus (Spheniscidae)

Abstract

The karyotype and the C-band pattern of Spheniscus magellanicus are described here for the first time. Peripheral blood samples from three females and four males were taken in Imbé (Rio Grande do Sul, Brazil). Long-time cultures of leukocytes were made in order to obtain mitotic metaphases. The diploid number was determined from the analysis of 30 metaphases. The karyotype of Spheniscus magellanicus presents 68 chromosomes. Pairs 1, 2, 4, 5 and 7 are submetacentric, pairs 6 and 10 are metacentric, pairs 3, 8 and 9 are telocentric, and the remaining ones are small telocentric chromosomes. The sex chromosomes Z and W are submetacentric. The study carried out with C bands demonstrated that the W chromosome is totally heterocromatic, while the Z chromosome does not present positive marks. Centromeric marks can be observed in the macrochromosomes and in some microchromosomes. The only observed difference found among this species and the previously analyzed Spheniscus demersus and Spheniscus humboldti, resides in the diploid number 72 and 78 of those species, respectively. These differences are observed exclusively at the level of microchromosomes, indicating a high homogeneity in the diploid number and chromosome morphology of this group.