Wednesday, December 7, 2016

[Ichthyology • 2014] Gymnotus capitimaculatus • A New Species of Electric Fish (Gymnotiformes: Gymnotidae) from rio Jucuruçu basin, northeastern Brazil

Gymnotus capitimaculatus 
 Rangel-Pereira, 2014 

A new species of Gymnotus, from the G. pantherinus species-group, is herein described from the rio Jucuruçu basin, a coastal river drainage located in the southern part of Bahia state, northeastern Brazil. Gymnotus capitimaculatus sp. n. differs from all congeners by having an pair of round blotches anteriorly positioned or under vertical passing through eye, on ventral portion of the head. Furthermore, Gymnotus capitimaculatus also differs from all members of the G. pantherinus species-group by having the following unique combination of characters states: tail with an unique series of bands or round spots; precaudal portion of trunk without bands but either with rounded and/or vermiculated spots; forty-five precaudal vertebrae; nine scales above lateral line at mid-body; anal-fin base length 75.2–78.6 % of TL; anus-anal fin length 101.4–122.8 % of HL; and branchial opening 38.5–45.0 % of HL.

Key words: Atlantic Forest, Biodiversity, electric eels, Gymnotus pantherinus complex, Knife-fish, taxonomy

Distribution. Known only from rio do Ouro, a tributary of the rio Jucuruçu, Itamaraju municipality, Bahia state, northeastern Brazil.

Etymology. Named capitimaculatus from the Latin subject capitis (head) and adjective maculatus (blotchy), due to the presence of a pair of blotches in the ventral portion of the head. 

Ecology. The specimens were collected in a clear water stream which topical width was about 1.5 m, depth ranged from 0.1 to 1 m and the bottom was composed of sand and small gravel. The matrix through where the stream flowed was composed of a mix of grass pasture and scarce riparian forest. Individuals were found deeply hidden among marginal vegetation and roots, mostly where the water flow was faster. Another species of the genus Gymnotus, belonging to the G. carapo species group, was found sympatrically, but not syntopically, since it was caught where the water flow was slower.

 Rangel-Pereira F.S. 2014. Gymnotus capitimaculatus, A New Species of Electric Fish from rio Jucuruçu basin, northeastern Brazil (Ostariophysi: Gymnotiformes: Gymnotidae). Vertebrate Zoology. 64(2); 169–175. 

Resumo: Uma nova espécie de Gymnotus, pertencente ao grupo de espécies G. pantherinus, é aqui descrita para a bacia do rio Jucuruçu, uma drenagem fluvial costeira localizada no sul do estado da Bahia, nordeste do Brasil. Gymnotus capitimaculatus sp. n. difere de todos seus congêneres por possuir a porção ventral da cabeça com um par de máculas posicionadas anteriormente ou sob vertical que passa pelo olho. Ademais, Gymnotus capitimaculatus também difere de todos os membros do grupo G. pantherinus pela seguinte combinação exclusiva de caracteres: cauda com uma única série de barras os manchas arredondadas; porção pré-caudal do tronco sem barras ou com manchas arredondadas ou vermiculadas; quarenta e cinco vértebras pré-caudais; nove escamas acima da linha lateral no meio do corpo; comprimento da base da nadadeira anal 75,2–78,6 % do TL; comprimento ânus-nadadeira anal 101,4–122,8 % do HL; e abertura branquial 38,5 –45,0 % do HL.

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