Abstract
ABSTRACT The present report represents the first cytogenetic description of Steindachneridion doceanum, great catfish which is currently at high extinction risk and it is listed as threatened on the red list of the Brazilian Ministry of the Environment, also are suggested karyotype relationships with other species of the same genus endemic from other river basins. The results revealed a diploid number of 2n = 56 and the karyotype composed of 18 metacentric, 20 submetacentric, 10 subtelocentric and 8 acrocentric chromosomes (NF = 104). The AgNORs and CMA3 signals were coincident in location occupying the short arm of an acrocentric chromosome pair (25th), in a secondary constriction. The 5S rDNA genes were localized on the short arms of one subtelocentric pair. C-banding revealed terminal blocks on the short arms on many chromosomes as well as terminal positive bands at the both ends of a submetacentric pair. C banding also revealed a large heterochromatic block in the secondary constriction (25th) region that was coincident with the AgNORs sites and CMA3+ bright bands. In spite S. doceanum represent an endemic taxon, in spite their geographic isolation their cytogenetic characteristics show similarities with other species of the genus.
Highlights
Original articleJournal homepage: www.scielo.br/ni Published online: 18 October 2018 (ISSN 1982-0224)
The genus Steindachneridion Eigenmann & Eigenmann, 1919, commonly known as “surubim” or “monjolo”, belongs to the Order Siluriformes, family Pimelodidae and has a restricted distribution in certain South America river basins (Lundberg and Littmann, 2003)
In November 5th, 2015, with the rupture of the Fundão Dam in Minas Gerais state, Brazil, 50 million m3 of rejects from the processing of iron ore were discharged in the Doce River main channel and their tributaries, destroying fish habitat and the aquatic ecosystem (IBAMA, 2015)
Summary
Journal homepage: www.scielo.br/ni Published online: 18 October 2018 (ISSN 1982-0224). The present report represents the first cytogenetic description of Steindachneridion doceanum, great catfish which is currently at high extinction risk and it is listed as threatened on the red list of the Brazilian Ministry of the Environment, are suggested karyotype relationships with other species of the same genus endemic from other river basins. The AgNORs and CMA3 signals were coincident in location occupying the short arm of an acrocentric chromosome pair (25th), in a secondary constriction. C-banding revealed terminal blocks on the short arms on many chromosomes as well as terminal positive bands at the both ends of a submetacentric pair. As marcações AgNORs e CMA3 foram coincidentes ocupando o braço curto de um par de cromossomos acrocêntricos (par 25), em uma constrição secundária. Os genes 5S rDNA foram detectados nos braços curtos de um par subtelocêntrico. Palavras-chave: AgNORs, Bagre Sulamericano, Banda C, Cariótipo, Espécie Ameaçada
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