Chromosome Studies in Gymnotus Carapo and Gymnotus Sp. (Pisces, Gymnotidae)

SUMMARY

Karyotype studies were carried out on two fish species of the family Gymnotidae. In five samples of Gymnotus carapo from different localities chromosome number varied from 2n = 42 to 2n = 54. Specimens from the Amazon Basin had 2n = 42 (Belém—State of Pará) and 2n = 48 (Humaitá - State of Amazonas); from the Paraná Basin, 2n = 52 (Brotas—State of São Paulo) and 2n = 54 (Botucatu—State of São Paulo); from the East Basins, 2n = 54 (Miracatu—State of São Paulo). These differences in diploid number were accompanied by differences in the number of acrocentric chromosomes present in the complement. Only one sample of Gymnotus sp., from Miracatu, was analyzed. Here the diploid number was 2n = 52 and the complement was similar to that of G. carapo from Brotas.