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Gymnotus capanema , a new species of electric knife fish (Gymnotiformes, Gymnotidae) from eastern Amazonia, with comments on an unusual karyotype
Author(s) -
Milhomem S. S. R.,
Crampton W. G. R.,
Pieczarka J. C.,
Shetka G. H.,
Silva D. S.,
Nagamachi C. Y.
Publication year - 2012
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.2012.03219.x
Subject(s) - biology , karyotype , meristics , zoology , killifish , cyprinidae , cytotaxonomy , nucleolus organizer region , genus , anatomy , evolutionary biology , genetics , fish <actinopterygii> , chromosome , fishery , gene
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, Pará, 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 2 n = 42 (30m/sm + 12st/a) exhibits a novel karyotype for the genus, with 2 n = 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 A 3 (CMA 3 ) 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 2 n in comparison to the karyotypes of other species of Gymnotus . The karyotype of G. capanema , with a reduced 2 n , is strikingly different from all other previously studied congeners.