Gymnotus capanema, a new species of electric knife fish (Gymnotiformes, Gymnotidae) from eastern Amazonia, with comments on an unusual karyotype

    Authors

    S. S. R. Milhomem; W. G. R. Crampton; J. C. Pieczarka; G. H. Shetka; D. S. Silva;C. Y. Nagamachi

    Comments

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    Abbreviated Journal Title

    J. Fish Biol.

    Keywords

    Amazon; chromosomal rearrangements; cytogenetics; FISH; reproductive; isolation; PISCES; CHROMOSOMES; CARAPO; BRAZIL; BASIN; ECOLOGY; REGIONS; Fisheries; Marine & Freshwater Biology

    Abstract

    Gymnotus capanema n. sp. is described on the basis of cytogenetic, morphometric, meristic and osteological data from nine specimens (one male and eight females) from the municipality of Capanema, Para, in the eastern Amazon of Brazil. Later, three additional specimens were found in museums and regarded as nontypes (not cytogenetically analysed). Gymnotus capanema, which occurs in sympatry with Gymnotus cf. carapo cytotype 2n = 42 (30m/sm + 12st/a) exhibits a novel karyotype for the genus, with 2n = 34 (20m/sm + 14st/a). Gymnotus capanema can be unambiguously diagnosed from all congeners on the basis of a combination of characters from external anatomy, pigmentation and osteology. The constitutive heterochromatin, rich in adenine-thymine (A-T) base pairs [4',6 diamidino-2-phenylindole dihydrochloride (DAPI) positive], occurs in the centromeric region of all of the chromosomes, and in the pericentromeric and the entire short arm of some chromosomes. The nucleolar organizing region (NOR), stained by silver nitrate, chromomycin A3 (CMA3) and 18S ribosomal (r)DNA fluorescence in situ hybridization (FISH), occurs in the short arm of pair 15. FISH, with telomeric probes did not show interstitial telomeric sequences (ITS), despite the reduced 2n in comparison to the karyotypes of other species of Gymnotus. The karyotype of G. capanema, with a reduced 2n, is strikingly different from all other previously studied congeners.

    Journal Title

    Journal of Fish Biology

    Volume

    80

    Issue/Number

    4

    Publication Date

    1-1-2012

    Document Type

    Article

    Language

    English

    First Page

    802

    Last Page

    815

    WOS Identifier

    WOS:000302289200006

    ISSN

    0022-1112

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