Gymnotus coropinae Hoedeman, 1962

Craig, Jack M., Correa-Roldán, Vanessa, Ortega, Hernán, Crampton, William G. R. & Albert, James S., 2018, Revision of Gymnotus (Gymnotiformes: Gymnotidae) from the Upper Madeira Basin of Bolivia and Peru, with descriptions of two new species, Zootaxa 4413 (1), pp. 111-132 : 119-120

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Gymnotus coropinae Hoedeman, 1962


Gymnotus coropinae Hoedeman, 1962

Figure 6C View FIGURE 6 , Table 1

G. anguillaris in part: Nijssen and Isbrücker, 1968

Diagnosis: Gymnotus coropinae is the only representative of the G. coatesi clade sensu Tagliacollo et al. (2016) present in the Upper Madeira, and can be easily differentiated from members of the G. carapo clade on the following characters: one, small maximum adult body size up to 135 mm TL in the G. coropinae of the Upper Madeira, vs. large (237–360 mm TL) in the G. carapo clade of the Upper Madeira; two, single laterosensory pore in the posterior corner of the preopercle vs. two in the G. carapo clade of the Upper Madeira; three, teeth all small and needle shaped teeth, vs. two to seven arrowhead-shaped in the G. carapo clade of the Upper Madeira; four, cylindrical body profile, vs. laterally-compressed in the G. carapo clade of the Upper Madeira.

Description: Sexually monomorphic. Size up to 162 mm TL with adult body proportions attained at 90–120 mm TL. Adult body shape subcylindrical with a mean ratio of body width to depth of 75%. Head length moderate, 7.9–11.6% total length. Snout length moderate, 29.3–34.5% head length. Mouth width intermediate, 33.2–46.1% head length. Preanal distance long, 88.4–120.3% head length. Anal-fin intermediate, 70.6–84.2% total length. Cycloid or ovoid scales present on entire post-cranial portion of body from nape to caudal appendage. Scales above lateral line intermediate, seven to eight, mode seven. Gape moderate, extending three quarters distance from anterior tip of snout to posterior nares. Mouth position superior, lower jaw longer than upper, rictus decurved. Chin round in lateral, dorsal profiles, fleshy and bulbous with mental electroreceptive organ overlying lower jaw. Anterior narial pore partially or entirely included within gape, pipe-shaped. Anterior nares large, half diameter of eye. Eye below horizontal with mouth. Circumorbital series ovoid. Anterior margin of ethmoid region rounded. Premaxilla with 11–12 (mode 12, n=2) teeth disposed in single row along outer margin, and four to five (mode five, n=2) in inner row. Outer row teeth large and needle shaped, inner teeth short and needle shaped, no arrowhead shaped teeth present. Curved median margin of premaxilla. Maxilla-palatine articulation near anterior tip of endopterygoid. Maxilla vertical, rod-shaped, broad distally with a straight ventral margin, length equal to roughly width of four to six dentary teeth. Dentary with outer row of 19–21 (mode 21, n=2) teeth, and inner row of 10–12 (mode 11, n=2), none arrowhead shaped. Outer row with one to 10 slender recurved needle-shaped teeth anteriorly, those posteriorly larger and less slender. Inner tooth row extending about two-thirds along the tooth-bearing portion of dentary bone. Teeth longer, more needle-shaped and closer-spaced anteriorly. Posterodorsal and posteroventral dentary processes abut at midlength. Dentary posteroventral process nearly as long as posterodorsal, narrow distally. Dentary ventral margin lamella wide, depth greater than posterior process. Dentary anteroventral margin rounded in lateral view, without a hook. Mandible long, extended, length greater than twice depth. Anguloarticular process long, extending beyond ventral margin of dentary. Retroarticular with an arched lamella posteriorly forming a small canal, posterior margin square. Metapterygoid superior and inferior portions approximately equal in size, ascending process robust, long, base shorter than length, curved, tip complex. Posterior lateral line fenestra contacting posterodorsal margin of hyomandibula. Preopercle with anteroventral notch, posterodorsal laterosensory ramus with two superficial pores, margin of medial shelf entire, median shelf small, less than half width of symplectic. Interopercle dorsal margin ascending process broad. Opercle dorsal margin straight to slightly convex, its posterior margin smooth. Opercular posterior margin entirely smooth. Subopercle dorsal margin concave. Cranial fontanels closed in juveniles and adults. Frontal shape broad, width at fourth infraorbital greater than that of parietal, anterior margin of straight, continuous with margins of adjacent roofing bones, postorbital process narrow, less than two times width of supraorbital canal. Adductor mandibula undivided at insertion, intermusculars absent. All basibranchials unossified. Gill rakers not contacting gill bar.

Cleithrum very narrow, ventral margin straight, anterior limb long, more than one-point-eight times ascending limb, deeply incised on its anteroventral margin, without large facet for insertion of muscle from supracleithrum. Postcleithrum thin, discoid or sickle shaped. Rib 5 robust along its entire extent, less than three times width of rib 6. Displaced hemal spines absent. Length anal-fin pterygiophores equal to or longer than hemal spines. Pectoral fin intermediate, with 13–14 rays, mode 13. Anal fin of moderate length, with 210–230 rays, mode 230. Single hypaxial electric organ, extending along entire ventral margin of body with 3 rows of electroplates near caudal insertion of anal fin.

Color in alcohol: Ground color dark brown in adults and juveniles. four to 20 (median 17, n =6) white or cream bands on lateral surface. In anterior one to two thirds of body of adults, bands absent, restricted to the ventral part of the lateral surface such that the dark interbands fuse into a uniform dark coloration anteriorly, or highly reduced in width. More anterior bands may extend onto dorsal part of lateral surface, but never meet bands from the other side of body. Pale bands with high-contrast margins, dark ground color, extending to mid-dorsum along posterior one quarter of body. Two to three pale bands posterior to last anal-fin ray. Pale bands never completely divided, but fainter coloration in middle of posterior-most three to six bands. Pale bands oriented vertically or obliquely in anterior-inferior to posterior-superior orientation. Pale bands irregular in shape, width, arrangement, both on and among individuals. Pale bands narrow and shorten anteriorly, only rarely extending to midline anteriorly. No pale bands meet on ventral midline, between anus and anal-fin origin. Area between pale bands infrequently marked by cream colored patch near ventral margin of anal-fin pterygiophores, especially posteriorly. Pale bands of juveniles resemble adults, sometimes extend further dorsally in anterior portion of body. Head never banded, characterized by dense speckling dorsally fading to pale yellow ventrally. Pectoral-fin rays dark brown, inter-radial membranes hyaline. Anal-fin membrane charcoal gray anteriorly, black posteriorly. No unpigmented patch at the caudal end.

Material Examined: Peru, Madre de Dios: MUSM 17596 (3), 90–112 mm TL , Río Madre de Dios (12°36’S, 069°11’W) GoogleMaps ; MUSM 20146 , 76 mm TL, Río Madre de Dios, Río Los Amigos, Parque Nacional Manu (12°34’36”S, 070°04’14"W) GoogleMaps ; MUSM 20264 (8), 50–118, Rio Los Amigos, CRA, Quebrada Moro Blanco, abajo Aguajal ; MUSM 20272 , 140 mm TL, Tambopata, Tambopata National Reserve, nr. Explorer’s Inn (12°50’12.01’S, 069°17’38.12’W) ; MUSM 3013 , 105 mm TL, Río Tambopata, Cochachica (~ 12°44’S, 069°11’W) GoogleMaps ; MUSM 4176 , 81 mm TL, same locality as MUSM 3013 GoogleMaps ; MUSM 4503 (2), 66–70 mm TL, Río Tambopata, cuenca del Río Heath, Quebrada San Antonio (~ 12°44’S, 69°11’W) GoogleMaps ; MUSM 535 (13), 79–136 mm TL; MUSM 7594, 76 mm TL; USNM 264102 View Materials (2), 112–114 mm TL, Río Tambopata, nr. Cochachica (~ 12°50’30”S, 069°17’31”W) GoogleMaps ; USNM 264108 View Materials (2), 117–121 mm TL, Río Tambopata, nr. Río la Torre (~ 12°49’40”S, 069°18’00”W) GoogleMaps ; USNM 366207 View Materials (3), 86–142 mm TL, Río Tambopata, nr. Cochachica (~ 12°49’45”S, 069°16’15”W) GoogleMaps ; USNM 366208 View Materials , 97 View Materials mm TL, Río Tambopata, nr. Río la Torre (12°50’S, 069°18’W) GoogleMaps .