Chromosomal and electric signal diversity in three sympatric electric knifefish species (Gymnotus, Gymnotidae) from the Central Amazon Floodplain

    Authors

    S. S. R. Milhomem; W. G. R. Crampton; J. C. Pieczarka; D. D. Silva; A. L. Cardoso; P. C. da Silva; J. A. de Oliveira;C. Y. Nagamachi

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    Abbreviated Journal Title

    Rev. Fish. Biol. Fish.

    Keywords

    Cytogenetics; Gymnotiformes; Reproductive isolation; Electric organ; CYTOGENETIC ANALYSIS; KARYOTYPE EVOLUTION; HYDROGRAPHIC BASINS; HOPLIAS-MALABARICUS; FISH; GYMNOTIFORMES; PISCES; CARAPO; BRAZIL; ELECTRORECEPTORS; Fisheries; Marine & Freshwater Biology

    Abstract

    We describe chromosomal and electric signal diversity in three sympatric species of Gymnotus (Gymnotidae) fish from the Central Amazon Floodplain. Gymnotus arapaima presents a karyotype of 2n = 44 (24 m-sm + 20st-a), G. mamiraua 2n = 54 (42 m-sm + 12st-a), and G. jonasi 2n = 52 (12 m-sm + 40st-a). No evidence for a chromosomal sexual system was observed in two species for which both males and females were analyzed (G. mamiraua and G. arapaima). In all three species the constitutive heterochromatin is located primarily in pericentromeric regions, but also at some other sites. G. arapaima and G. mamiraua exhibit simple nucleolar organizing regions (NORs) on short arms of chromosome pairs 19 and 24, respectively. Gymnotus jonasi exhibits a multiple interstitial NOR on the long arm of pairs 9 and 10, and on the short arm of pair 11. G. arapaima and G. mamiraua exhibit several additional similarities in their karyotypic formulas-reflecting the phylogenetic proximity of these species within a G. carapo group clade (based on molecular phylogenetic evidence). The chromosomal differences among these three sympatric species imply complete post-zygotic reproductive isolation. A prominent pattern of partitioning of the peak power frequency of the electric organ discharge of these three species indicates pre-zygotic reproductive isolation of mate attraction signals. We conclude by discussing the evolutionary events that may have promoted signal divergence and reproductive isolation in Gymnotus of the Central Amazon, and the role that chromosomal rearrangements may place in diversification.

    Journal Title

    Reviews in Fish Biology and Fisheries

    Volume

    22

    Issue/Number

    2

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    485

    Last Page

    497

    WOS Identifier

    WOS:000303894300008

    ISSN

    0960-3166

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