Gymnotus paraguensis, James S. Albert & William G. R. Crampton, 2003

James S. Albert & William G. R. Crampton, 2003, Seven new species of the Neotropical electric fish Gymnotus (Teleostei, Gymnotiformes) with a redescription of G. carapo (Linnaeus)., Zootaxa 287, pp. 1-54 : 34-36

Gymnotus paraguensis n. sp. Albert and Crampton

(Fig. 7; Tables 2 and 3)

Holotype: UMMZ 206155 (1), 222 mm, collected 27 June, 1983, at Itapua, Arroyo Tembey, 7.4 km SW of San Rafael, Río Parana drainage, Paraguay (26°35'S, 55°34'W) by R. Bailey, J. Taylor, T. Grimshaw, P. Myers, and L. Creighton.

Paratype: UMMZ 240700, 193 mm, collected with holotype.

Nontypes: 3 lots, 3 specimens. FMNH 108546 (1), 164 mm, 03 November, 1998, at Río Nueva in Brejo do Santo Sofia, Mato Grosso do Sul, Brazil. NRM 42380 (in part) (1 of 2), 240 mm, 28 February, 1988, at Saltos da Guaira, Mulle Ytaipú, Canindeyú, Río Paraná drainage, Paraguay (24°03'44" S, 54°18'W).

Diagnosis. Gymnotus paraguensis can be distinguished from other species of the G. carapo species-group by: 1, a color pattern composed of regularly arranged, unpaired (evenly pigmented), dark bands with straight, high contrast margins, with 4-7 inverted Y- shaped, or sometimes X-shaped, or discontinuous dark pigment bands in middle to posterior portions of body; 2, many short lateral line ventral rami (49-55 [median 51, n=3]). Gymnotus paraguensis is most similar to G. choco from the Pacific slope of Colombia, from which it can be distinguished by characters provided in the diagnosis of G. choco (above). Gymnotus paraguensis can be further distinguished from other taxa of the G. carapo species-group by the unique combination of character states provided in Table 4.

Description. Fig. 7 illustrates head and body shape and pigment patterns. Morphometric data in Table 2 and meristic data in Table 3. Size up to 224 mm. Size at reproductive maturity and sexual dimorphism unknown. Scales present on entire post-cranial portion of body from nape to caudal appendage. Scales above lateral line large, 6 to dorsal midline at midbody Scales ovoid over most of body, 1.5 times as long as deep. Gape size in mature specimens large, extending to or beyond posterior nares. Mouth position superior, rictus decurved. Eye position below horizontal line from front of mouth. Anterior narial pore partially or entirely included within gape. Circumorbital series ovoid. Caudal appendage short, less 0.5 times length of pectoral fin. Single hypaxial electric organ, extending along entire ventral margin of body. Electric organ discharge not known.

Many osteological features not known due to paucity of specimens for clearing and staining; some character states were determined from radiographs. Dorsoposterior laterosensory ramus of preopercle with two superficial pores. Cranial fontanels closed in juveniles and adults. Anterior margin of frontal straight, continuous with margins of adjacent roofing bones. Frontal shape narrow, width at fourth infraorbital less than that of parietal. Anterior limb of cleithrum long, more than 1.8 times ascending limb. Rib 5 robust along its entire extent, less than 3 times width of rib 6. Hemal spines present. Displaced hemal spines absent. Multiple anal-fin ray branching posterior to rays 10-17. Lateral line dorsal rami absent in adults. Length anal-fin pterygiophores equal to or longer than hemal spines.

Color in alcohol. Ground color of body pale brown without countershading. Chromatophores not concentrated along dorsum near midline. Body with 23-26 (median 24, n=3) dark brown obliquely oriented pigment bands (or band-pairs) extending from tip of tail to nape. Dark bands evenly pigmented along entire body with band margins as dark as band middles. Bands meet on mid-dorsum along entire body length. Interband contrast similar along entire body axis. Three dark bands from either side meet on ventral midline, between anus and anal-fin origin.

Head not banded, its ground color dark brown dorsally grading to lighter brown ventrally, without freckles and with numerous speckles distributed over branchiostegal membranes and ventral surface of head. Pectoral-fin rays brown, interradial membranes hyaline. Anal-fin membrane divided into three parts along body axis: anterior 40% brown, mid 40% black, posterior 20% translucent.

Distribution. Known only from the Río Paraguay basin; in Paraguay from the Río Itapua, and Brazil from the Rio Nueva, Mato Grosso do Sul (Fig. 4).

Common name. Tuvira (Brazil), morenita (Argentina).

Etymology. The specific epithet is named for the Río Paraguay. An adjective.