Trends in the karyotypic evolution of the Neotropical catfish family Heptapteridae Bockmann 1998 (Teleostei: Siluriformes) |
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Authors: | Rafael Splendore de Borba Edson Louren?o da Silva Ana Carolina Sales Pacheco Patricia Pasquali Parise-Maltempi Anderson Luis Alves |
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Institution: | (1) Departamento de Biologia, Laborat?rio de Citogen?tica, Instituto de Bioci?ncias, UNESP Univ Estadual Paulista “Julio de Mesquita Filho”, Av. 24A, 1515, Rio Claro, SP, 13506-900, Brazil;(2) Present address: Embrapa Pesca e Aquicultura, Av. Juscelino Kubitscheck, Conjunto 1, Lote 17, 103 Sul, Palmas, TO, 77015-012, Brazil; |
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Abstract: | The Heptapteridae family is endemic to the Neotropics and is one of the most representative members of the Siluriformes order
in small bodies of water. Due the lack of data for clearly distinguishing their species, only recently was elevated from condition
of subfamily to family. However, many doubts about certain species remain yet. There are a relatively large number of cytogenetics
studies about heptapterids that permits comparative analyses focused in the karyotype evolution of the group. However, the
absence of studies about this theme motivated this work. Were analyzed cytogenetically most representative species of the
family: Rhamdia, Imparfinis, Pimelodella, Phenacorhamdia, and Taunaya, and compared with available data from the family. The comparative analysis indicated the predominance of biarmed chromosomes
and low variation of the diploid number (around 2n = 58) suggesting that centric inversions were more important than centric
fissions in the history of heptapterids. It is corroborated by a remarkable number of NOR phenotypes mainly in Imparfinis and Rhamdia species. A probable condition of Heptapteridae plesiomorphic karyotype would be one composed of 2n = 58 chromosomes of types
metacentric and submetacentric mainly, with simple NOR at the sub terminal position. The reduction of diploid number, it would
possibly through successive events of chromosome fusion with deletions and inversion rearrangements responsible for NOR variation
within the certain genus. The occurrence of B chromosomes is from a derived event, possibly of recent origin, without phylogenetic
implications. |
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