Gymnotus javari, 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 : 39-43

Gymnotus javari n. sp. Albert, Crampton and Hagedorn

(Fig. 9; Tables 2 and 3)

Holotype: UMMZ 224599, 197 mm, collected 15 May, 1993 at Quebrada Caraná nr. Buen Sucesso, Río Yavari (Rio Javarí), Loreto Department, Peru (04°22'S, 70°31'W) by J. Albert and T. DiBenedetto.

Paratypes: UMMZ 224596 (10), 45-175 mm, collected with holotype. UMMZ 240971, 162 mm, collected with holotype.

Nontypes: 11 lots with 40 specimens. IIAP uncat. (1), 201 mm, no date, nr. Iquitos Loreto Department, Peru (03°46'S, 73°15'W). MCZ 60005 (8), 70-208 mm, 19 September 1865, at Tabatinga, Rio Solimões, Amazonas State, Brazil (04°16'S, 69°56'W). MUSM 14480b (1), 85 mm, October 1993, at Río Aguarico, Río Napo drainage, Napo State, Ecuador (01°00'S, 75°12'W). MUSM 14481 (8), 72-124 mm, no date, same locality data as MUSM 14480b. MUSM 3234 (2), 51-102 mm, 16 February, 1992, at Jenaro Herrera, Río Ucayali, Loreto Department, Peru (05°03'S, 73°50'W). NRM 13521 (1), 93 mm, 12 July 1981, nr. Pebas in floating meadows, Río Ampiyacu, Loreto Department, Peru (03°20'S, 71°49'W). NRM 27702 (2), 47-51 mm, 31 July, 1984, at stream nr. Colonia Angamos, Río Yavari, Loreto Department, Peru (05°11'S, 72°53'W). UF 122824 (1), 141 mm, 21-28 May, 2002, nr. Iquitos, Loreto Department, Peru (03°46'S, 73°15'W). UMMZ 224601 (1), 132 mm, 4 May, 1993, at Río Tahwayo nr. Santa Ana, Loreto Department, Peru (04°5'S, 73°0'W). UMMZ 224607 (5, in part), 29-106 mm, 4 May, 1993, at Bora Indian village nr. Amazon camp, Río Momon, nr. Iquitos, Loreto Department, Peru (03°46'S, 73°15'W).

Diagnosis. Gymnotus javari can be distinguished from other species of the G. pantherinus species-group by a unique color pattern composed of narrow pale bands (about 1/4 width of dark bands) on anterior half of body, approximately equally narrow dorsally and ventrally, and 5-8 partially divided, often H-shaped dark bands on posterior half of body. Gymnotus javari can be further distinguished from other species of the G. pantherinus species-group by the following unique combination of characters: head depth moderate (HD 55.6-64.7% HL [mean 59.9, n=12] vs. 53-55% or 66-75%); and large scales, with 7-9 (mode 8, n=11) scale rows above lateral line to dorsal midline at midbody.

Gymnotus javari is most similar to G. coatesi from which it can be distinguished by: 1, a unique color pattern (see above) (vs. pale bands as broad as dark bands on anterior half of body, pale bands broader dorsally, and dark bands undivided on posterior half of body); 2, a more laterally compressed adult body (BW 61-77% BD [mean 69%, n=12] vs. 76- 86% [mean 83%, n=4]); 3, a wider head (HW 56-66% HL [mean 63%] vs. 50-56% [mean 53%]); 4, more scales over the anal-fin pterygiophores (APS 9-10 rows [mode 9, n=5] vs. 6-7 rows [mode 7, n=3]); and 5, fewer ventral lateral line rami (VLR 10-15 [mode 13, n=5] vs. 19-23 [mode 22, n=3]).

Gymnotus javari is also similar to G. jonasi from the Western Amazon and Rio Madeira basin, from which it can be distinguished by: 1, a unique color pattern (see above); 2, a larger maximum body size (201 mm vs. 150 mm); 3, a wider mouth (MW 32- 42% HL [mean 37%, n=12] vs. 31-33% [mean 33%, n=4]; 4, a shorter pectoral fin (P1R 40-48% [mean 42, n=12] vs. 52-55% [mean 54%, n=4]); 5, more anal-fin rays (AFR 180- 240 [mean 200, n=13] vs. 135-165 [mean 152, n=6]); 6, more scales above the anal-fin pterygiophores (AFP 9-10 [mode 9, n=2] vs. 5-6 [mode 5, n=6]); 7, more precaudal vertebrae(PCV 40-44 [mode 42, n=14] vs. 36-39 [mode 37, n=9]); 8, more pored scales to the first ventral lateral line ramus (PLR 52-67 [mean 59, n=11] vs. 31-40 [mean 36, n=6]); 9, more pored lateral line scales (PLL 88-108 [mean 98, n=5] vs. 73-76 [mean 75, n=5]); 10, fewer ventral lateral line rami (VLR 10-15 [mean 13, n=5] vs. 16-25 [mean 20, n=5]).

Gymnotus javari is also similar to G. stenoleucus from the Venezuelan Amazon, from which it can be distinguished by: 1, a unique color pattern (see above); 2, a larger maximum body size (201 mm [n=21] vs. 142 mm [n=9]); 3, fewer pale lateral bands (BND 13- 21 [mode 15, n=11] vs. 18-24 [mode 22, n=9]); 4, more pectoral-fin rays (P1R 12-14 [mode 13, n=8] vs. 13-15 [mode 14, n=11]); 5, more scales over anal-fin pterygiophores (AFP 9-10 vs. 7-8 rows).

Description. Fig. 9 illustrates head and body shape and pigment patterns. Morphometric data in Table 2 and meristic data in Table 3. Size up to 201 mm. Size at reproductive maturity and sexual dimorphism unknown. Circular scales present on entire post-cranial portion of body from nape to tip of caudal appendage. Gape size in mature specimens large, extending to or beyond posterior nares. Mouth position superior, rictus decurved. Eye position lateral, lower margin of eye dorsal to horizontal with rictus. Circumorbital series ovoid.

Mesethmoid anterior margin concave with small paired anterolateral processes. Mesethmoid neck broad, more than width of ventral ethmoid. Anterior narial pore partially or entirely included within gape. Maxilla-palatine articulation near anterior tip of mesopterygoid. Maxilla orientation vertical. Maxilla rod- or paddle-shaped with straight ventral margin. Maxilla length equal to width of 7-9 dentary teeth. Maxilla broad distally, paddleshaped. Premaxilla with 11-16 teeth along outer margin. Median margin of premaxilla curved. Premaxilla with two tooth rows, or one row with an inner patch anteriorly. Dentary with one or two tooth rows, including 5 or more needle-shaped teeth. Dentary outer tooth row with 16 or more teeth. Dentary with short inner row or patch of teeth anteriorly. Dorso- and ventro-posterior dentary processes abut, ventro- shorter than dorsoposterior process. Dentary dorsoposterior process narrow distally. Dentary ventral margin with a narrow lamella, less than posterior process. Dentary with pronounced ventroposteriorly oriented hook at mental symphysis. Dorsal margin of opercle straight or slightly convex. Texture of dorsal opercle process deeply pitted and cancellous. Dorsal opercular crest absent or small. Posterior margin of opercle smooth, entire, without spines or processes. Ventral ridge field of opercle broad. Dorsal ridge field of opercle short, less half opercular width. Dorsoposterior laterosensory ramus of preopercle with single superficial pore. Preopercle with anteroventral notch. Margin of preopercular medial shelf entire. Median shelf of preopercle small, less than half width of symplectic. Ascending process of mesopterygoid robust, long, its base shorter than its length. Mesopterygoid ascending process straight. Tip of mesopterygoid ascending process simple. Metapterygoid small, its superior portion less ossified than its inferior portion. Dorsal margin of interopercle with broad ascending process. Dorsal margin of subopercle concave. Posterior margin of retroarticular square. Retroarticular with an arched lamella posteriorly, forming a small canal. Anguloarticular process short, to ventral margin poster. Mandible long, extended, its length more than twice its depth. Hyomandibular trigeminal canals (supraorbital, infraorbitral), connected. Posterior lateral line fenestra contacting dorsoposterior margin of hyomandibula. Cranial fontanels closed in juveniles and adults. Anterior margin of frontal straight, continuous with margins of adjacent roofing bones. Frontal postorbital process narrow, less than two times width of supraorbital canal. Frontal broad, its width at fourth infraorbital subequal to that of parietal. Lateral ethmoid absent. Parasphenoid posterior processes narrow. Parasphenoid lateral process broad, triangular. Parietal rectangular, its length less than width. Pterosphenoid anteroventral portion robust, extending ventral to lateral margin of parasphenoid. Prootic foramen Vp combined with V2-3+VII. Adductor mandibula undivided at insertion. Adductor mandibula intermusculars absent. All basibranchials unossified. Gill rakers not contacting gill bar. Basibranchial 5 unossified. Pectoral fin of moderate size, with 14-16 rays. Pectoral fin, medial radial small. Mesocoracoid elongate, its length more than 4 times width. Postcleithrum thin, discoid or sickle-shaped. Cleithrum very narrow, ventral margin straight. Anterior limb of cleithrum long, more than 1.8 times ascending limb. Cleithrum anterior notch absent. Cleithrum without large facet for insertion of muscle from supracleithrum. Rib 5 broad, with a large medial triangular shelf. Hemal spines present. Displaced hemal spines absent. Multiple anal-fin ray branching posterior to rays 18 or more. Lateral line dorsal rami absent in adults. Length anal-fin pterygiophores equal to or longer than hemal spines. 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 with four phases away from baseline in adults.

Color in life and in alcohol. Ground color of body dark brown. Body with 13 to 21 (median 15, n=11) alternating pale-yellow (or cream) and dark chocolate brown pigment bands, vertically oriented on posterior half of body and slightly oblique on anterior half of body. Pale bands generally regular in form, width, and arrangement, although variable in number among individuals. Band-interband margins regular and straight. 5-8 dark bands partially or completely divided (H-shaped) on posterior half of body. Dark bands about four times as broad as pale bands on anterior half of body. Pale bands never branched, and extending to dorsal midline along entire extent of body. One or rarely two pale bands meet at ventral midline between anus and anal-fin origin. One or two pale bands posterior to last anal-fin ray.

Head not banded or blotched, its ground color dark brown dorsally grading to lighter brown ventrally, with numerous freckles and speckles distributed over entire surface. Pectoral-fin rays brown or gray, interradial membranes hyaline. Anal-fin membrane hyaline, anal-fin rays brown.

Ecology. The types of G. javari were collected from the lower reaches of meandering upland (non-floodplain) streams, in undercut banks and submerged vegetation. Other specimens pertaining to G. javari were collected from rootmats of whitewater floodplain floating meadows, near the margins of rivers channels and lakes. Specimens from the Río Aguarico, Ecuador, were caught in small streams with clay sides, silt or vegetation bottom, pH 5.5-6.0, conductivity 15 microsemens/cm, air temp, 34.8 °C, water temp 24.6°C, surface flow 4.6 cm/s, secchi depth 120 cm, stream depth, 1-4 m, width 4-8 m (M. Hagedorn pers. obs.).

Distribution. Known from the Western Amazon, from the Río Amazonas, the lower portions of the Napo, Javarí, and Ucayali basins (Fig. 10).

Common name. Macana (Peru), sarapó (Brazil). Etymology. Named for the Rio Javarí. A noun in apposition.