Gymnotus tigre, 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 : 36-39

Gymnotus tigre n. sp. Albert and Crampton

(Fig. 8; Tables 2 and 3)

Holotype: UF 25552, 411 mm, collected 11 November, 1973, in floating macrophytes along north shore of Río Amazonas nr. Leticia, Colombia (04°09'S, 69°57'W) by D. Taphorn.

Paratypes: UF 128412 (1), 332 mm, collected with holotype. ICNMHN 6690 (1), 340 mm, 26 July, 1992, same locality data as holotype by L. Jimenez.

Nontypes: 5 lots with 5 specimens. IAVHP 0615 (1), 179 mm, regenerated caudal appendage, 19 September, 1973, nr. Leticia, Amazonas Department, Rio Amazonas, Colombia (04°09'S, 69°57'W). INPA 6814 (1), 113 mm, 20 October, 1991, at Ilha Terra Grande, Rio Jamanxim, Rio Tapajós drainage, Pará State, Brazil. FMNH 97389 (1), 292 mm, November, 1956, at Río Bobonaza, nr. Canelos, Río Pastaza drainage, Pastaza Department, Peru (01°39'S, 77°46'W). UF 117112 (5), 89-171 mm, acquired from fishermen 04 January 1993, Río Amazonas nr. Iquitos, Loreto Department, Peru (03°46'S, 73°15'W). UF 122821 (1), 331 mm, acquired from fishermen 28 May, 2002, same locality data as UF 117112. NRM 27644 (1), 104 mm, 02 July 1986 at El Estrecho, Río Putumayo, Loreto Department, Peru (02°28'S, 72°42'W).

Diagnosis. Gymnotus tigre can be distinguished from all congeners except G. henni (from the Pacific Slope of Colombia) by the presence of irregular pale-yellow blotches on chin, behind and under eyes, over opercle, and between eyes. Gymnotus tigre can be further distinguished from other species of the G. carapo species-group (except G. henni ) by: 1, pale yellow bands on body with straight, high contrast margins, as broad or broader than brown bands anteriorly; 2, obliquely oriented hyaline and dark stripes at caudal end of anal fin. Gymnotus tigre can be distinguished from other species of the G. carapo species-group except G. esmeraldas (from the Pacific Slope of Ecuador) by the presence of more (46-48; mode 47 vs. 32-44) precaudal vertebrae, and from G. esmeraldas by the presence of pigment bands. Gymnotus tigre 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. 8 illustrates head and body shape and pigment patterns. Morphometric data in Table 2 and meristic data in Table 3. Size up to 411 mm. Size at reproductive maturity and sexual dimorphism unknown. All scales highly elongate on their anteroposterior axis; approximately 3-5 times as long as deep at midbody, 1.5-2 times as long as deep at posterior region of caudal filament, their proportional elongation increasing with body size. Gape size in mature specimens small, not to anterior nares. Mouth position superior, rictus decurved. Eye position below horizontal line with 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 unavailability 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. 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 yellow without countershading. Chromatophores not concentrated along dorsum near midline. Body with 16-23 (mode 23) pairs of dark bands on extending from tip of tail onto head. Band-pairs vertical above lateral line and obliquely oriented below lateral line. Band appearance more regular anteriorly with 4-5 X or Y-shaped pale-yellow interband regions posteriorly. Band-interband margins irregular and wavy. Bands divided along entire body with margins much darker than middles, with greatest pigment densities along the outer edge of band margins. Bands meet on mid-dorsum along entire body length. Interband contrast similar along entire body axis. Three faint dark bands from either side meet on ventral midline, between anus and anal-fin origin.

Head ground-color dark chocolate with irregular pale-yellow blotches on chin, behind and under eyes, over opercle, and between eyes. Dark regions on head composed of numerous dark brown chromatophores with greatest pigment densities along outer edge of pale blotches. Branchiostegal membranes and ventral surface of head lightly speckled. Pectoral-fin interradial membranes dusky or hyaline. Color of anal-fin membrane graded along body axis, from light brown or hyaline anteriorly to dark brown or black posteriorly. Irregularly arranged hyaline and dark stripes extending obliquely to fin base along posterior most 10% of anal fin.

Distribution. Known from the Río Amazon basin, from the Río Pastaza basin in Ecuador to the Tapajós basin in Brazil (Fig. 4).

Common name. Macana tigre (Peru).

Etymology. Specific epithet from the common name used in the local aquarium trade referring to the tiger-like markings. A noun in apposition.