Gymnotus henni, 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 : 32-34

Gymnotus henni n. sp. Albert, Crampton, and Maldonado

(Fig. 6, Tables 2 and 3)

Holotype: CAS 47290, 308 mm, collected in 1913, at a creek nr. mouth of Río Calima, Río San Juan drainage, north of Buenaventura, Valle de Cauca Department, Colombia (03°53'N, 77°04'W) by A. Henn.

Paratypes: CAS 217162, collected with holotype, 145 mm. FMNH 56793 (2), 254- 273 mm, collected with holotype.

Nontypes: 5 lots with 13 specimens, all collected in Colombia: ICNMHN 96 (7), 127- 371 mm (all with regenerated caudal appendages), November, 1959, Río Baudó, Chocó Department. ICNMHN 102, (1), 237 mm (damaged caudal appendage), November, 1959, Río Baudó nr. Pavarandó, Chocó Department. ICNMHN 2284 (1), 346 mm, March, 1994, Río Baudó over road to Pie de Pepe, Upper Río San Juan, Pueblo Rico, Risaralda Department (05°07'N, 76°50'W). IMCN 1369 (1), 333 mm, 01 June, 2002, Resguardo Puerto Pizarro, Río San Juan, Litoral del San Juan, Chocó Department. USNM 246793 (3), 131- 314 mm, 31 August, 1967, at creek off Río Juradó, Chocó Department (07°06'N, 77°46'W).

Diagnosis. Gymnotus henni differs from other species in the Gymnotus carapo species-group except G. tigre n. sp. (see below) in the following aspects of pigmentation: 1, head with brown ground color and irregularly shaped pale-yellow blotches located on chin, gular area, behind and under eyes, over opercle, and between eyes; 2, pale yellow bands as broad or broader than dark brown bands on anterior half of body; 3, obliquely oriented hyaline and dark stripes at caudal end of anal fin. Gymnotus henni is most similar to G. tigre n. sp. from the Amazon basin from which it can be distinguished by: 1, fewer pigment band-pairs (BND 13-16 [median 15, n=7] vs. 16-23 [median 21, n=6]); 2, a wider mouth (MW 43.2-49.4% HL [mean 46.6%, n=7] vs. 40.4-43.9% [mean 42.7%, n=6]); 3, more slender body (BD 7.2-9.8% HL [mean 8.3%, n=7] vs. 8.9-10.0% [mean 9.4%, n=6]); 4, shorter head (HL 9.2-10.7% TL [mean 9.9%, n=7] vs. 9.9-13.3% [mean 11.1%, n=6]); 5, longer preanal distance (PA 72.1-112.3% HL [mean 94.4%, n=7] vs. 69.7-81.9% [mean 74.8%, n=6]); 6, presence of dorsal lateral line rami (vs. absent in G. tigre n. sp.). Gymnotus henni can be further distinguished from other taxa of the G. carapo speciesgroup by the unique combination of character states provided in Table 4.

Description. Fig. 6 illustrates head and body shape and pigment patterns. Morphometric data in Table 2 and meristic data in Table 3. Size up to 312 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 on body elongate, 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 in mature specimens large, extending to or beyond posterior nares. Mouth position superior, rictus decurved. Eye position below horizontal 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. Anterior margin of frontal straight, continuous with margins of adjacent roofing bones. Displaced hemal spines absent. Multiple anal-fin ray branching posterior to rays 10-17. 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 14-16 (median 16) pairs of dark band-pairs extending from nape to tip of tail head. Band-pairs vertical above lateral line and obliquely oriented below lateral line. Band-interband margins irregular and wavy. Bands completely divided forming band-pairs on anterior half of body, and 2-4 H- or X-shaped band-pairs connected by dark cross-bars in pale-yellow interband regions posteriorly. Bands meet on mid-dorsum along entire body length. Interband contrast similar along entire body axis. Two to four 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 side of chin, behind and under eyes, over opercle, and between eyes. Dark regions on head composed of numerous dark brown chromatophores with even pigment densities. 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, with an irregularly arranged set of hyaline and dark stripes extending obliquely to fin base along posterior most 10% of anal fin.

Distribution. Known from two rivers on the Pacific Slope of Colombia; the Río Calima, Valle de Cauca Department, and the Río Juradó, Chocó Department (Fig. 4).

Common name. Mayupa.

Etymology. Named for Arthur W. Henn, a pioneer in Neotropical ichthyology, who collected the types specimens of this species. An adjective.