Heteromorphic sex chromosome system with an exceptionally large Y chromosome in a catfish Steindachneridion sp. (Pimelodidae).
The chromosomes and banding patterns of Steindachneridion sp., a large catfish (Pimelodidae), endemic to the Iguaçu River, Brazil, were analyzed using conventional (C-, G-banding) and restriction enzyme banding methods. The same diploid number (2n = 56) as in other members of the genus and the family was found but the karyotype displayed an XX/XY sex chromosome system. The X chromosome was the smallest submetacentric, while the Y was the largest chromosome in the karyotype. Meiotic analysis showed 27 autosomal bivalents plus one heteromorphic XY bivalent during spermatogenesis. Sex chromosomes had no particular pattern after C-banding but G- and restriction enzyme bandings showed specific banding characteristics. The present finding represents the first report of a well-differentiated and uncommon sex chromosome system in the catfish family Pimelodidae.
Universidade Estadual de Londrina, Centro de Ciências Biológicas, Londrina, PR, Brazil. szwarcy@bol.com.br
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D000818:Animals; D002397:Catfishes / Q000235:genetics*; D002871:Chromosome Banding; D002874:Chromosome Mapping; D005260:Female; D008297:Male; D008540:Meiosis; D013093:Spermatogonia / Q000166:cytology / Q000648:ultrastructure; D014960:X Chromosome / Q000235:genetics / Q000648:ultrastructure; D014998:Y Chromosome / Q000235:genetics* / Q000648:ultrastructure