Gymnotus carapo madeirensis Craig, Crampton and Albert, 2017 :428

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 : 116-117

Gymnotus carapo madeirensis Craig, Crampton and Albert, 2017:428

Figure 6A , Table 1

Description: Gymnotus carapo madeirensis differs from all sympatric members of the G. carapo clade on the following characters: one, large maximum adult body size (up to 360 mm TL vs. 237–275 mm TL in the G. carapo clade of the Upper Madeira; two, a color pattern consisting of 16–25, mode 24 obliquely-oriented dark bands with wavy, irregular margins from nape and to tip of caudal appendage vs. dark bands greater than twice width of pale bands in G. eyra and G. riberalta and anteriormost two to three pale interbands crescent-shaped in G. chaviro . Sexually monomorphic. Size up to 360 mm TL with adult body proportions attained at about 130 mm TL. Adult body shape subcylindrical with a mean ratio of body width to depth of 67%. Head length moderate, 17.8–27.5% total length. Snout length moderate, 32.3–34.9% head length. Mouth width narrow, 38.6–49.0% head length. Preanal distance long, 65.2–84.0% head length. Anal-fin long, 74.9–83.8% total length. Cycloid or ovoid scales present on entire post-cranial portion of body from nape to caudal appendage. Scales above lateral line intermediate, five to seven, mode seven. Scales over anal-fin pterygiophores large, with eight rows. Gape large, extending to or beyond 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, in small narial fold. Anterior nares large subequal to eye diameter. Eye below horizontal with mouth. Circumorbital series ovoid. Premaxilla with 11–16 (mode 14, n=10) teeth disposed in single row along outer margin, arrowhead shaped anteriorly, conical posteriorly. Curved median margin of premaxilla. Maxilla-palatine articulation near anterior tip of endopterygoid. Maxilla vertical, rod-shaped, narrow distally with a straight ventral margin, length equal to roughly width of four to six dentary teeth. Dentary with one row of 16–19 (mode 17, n=4) teeth, two to four arrowhead shaped anteriorly, all others conical posteriorly. Posterodorsal and posteroventral dentary processes abut at midlength. Dentary posteroventral process nearly as long as posterodorsal, narrow distally. Dentary ventral margin lamella narrow, depth less than posterior process. Dentary anteroventral margin rounded in lateral view, without a hook. Mandible long, extended, length greater than twice depth. Retroarticular with an arched lamella posteriorly forming a small canal, posterior margin square. Anguloarticular process long, extending beyond ventral margin of dentary. Metapterygoid superior and inferior portions approximately equal in size, ascending process robust, long, base shorter than length, curved, tip simple. Hyomandibular trigeminal canals connected. Dorsal region of hyomandibula with four lateral foramenae, supraorbital and infraorbital nerves divided. 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 large, more 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 narrow, width at fourth infraorbital less than that of parietal, anterior margin of straight, continuous with margins of adjacent roofing bones, postorbital process broad, more than two times width of supraorbital canal. Lateral ethmoid unossified. Parietal rectangular, length less than width. Parasphenoid anteroventral portion robust, extending ventral to lateral margin of parasphenoid, posterior processes narrow. Prootic foramen Vp separate from V2-3 +VII. Adductor mandibula undivided at insertion, intermuscular bones absent. All basibranchials unossified. Gill rakers not contacting gill bar.

Cleithrum 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. Body cavity of moderate length, with 32–36 precaudal vertebrae, mode 33, n=41. 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 13–16 rays, mode 13. Anal fin of moderate length, with 210–268 rays, median 228. Single hypaxial electric organ, extending along entire ventral margin of body with three to four rows of electroplates near caudal insertion of anal fin.

Color in Alcohol: Body ground color tan ventrally grading to darker brown dorsally in adults, pale yellow throughout in smaller specimens. Bands variable in number among individuals and in shape and arrangement within individuals, uncorrelated with sex. Adults (TL> 200 mm TL) with 16–25 (mode 24, n=8) obliquelyoriented, chocolate-colored bands with wavy, irregular margins on lateral surface from nape and to tip of caudal appendage, occurring singly or as band-pairs (increasingly divided and irregular with size). Band-interband contrast increases ventrally and caudally, fades with growth (juveniles> 150 mm TL with distinct margins, specimens 200–300 mm TL faintly banded, and some specimens over 250 mm TL unbanded except very faintly in posterior one third of body). Band-interband contrast increases ventrally and caudally, fades with growth (juveniles with distinct margins, adults faintly banded, some specimens over 250 mm TL unbanded except very faintly in posterior one third of body). Bands may be divided dorsally or ventrally to form X - or inverted Y -shaped patterns. Pale inter-bands roughly one third width of dark bands at mid-body. Head never banded, characterized by dense speckling dorsally fading to pale yellow ventrally. Numerous chromatophores speckled over branchiostegal membranes and ventral surface of head. Pectoral-fin rays brown, interradial membranes hyaline. Anterior 80% of anal fin membrane dark brown, gray or black, posterior 20% translucent.

Materials Examined: Bolivia: UF 82191, 187 mm, Santa Cruz, Río Guaporé, Río San Pablo , Río San Diablo, Velasco, 71 km N. San José de Chiquitos (17°18’S, 60°35’W) ; UF 82211 (2), 196–205 mm, same locality as UF 82191; UF 82345 (3) 111–360 mm, Santa Cruz, Río Jorge, W. of Warnes, Río Piray (17°34’12”S, 63°12’36”W) ; UF 82470 (2), 170–218 mm, Beni, Río Mamoré, Río Ibaré , Cercado, Arroyo San Javier (14°38’S, 64°53’W) ; UF 82485, 360 mm, Beni, Río Mamoré, Río Ibaré , Cercado, 20 km N San Javier (14°28’S, 64°56’W) ; UF 82510, 241 mm, Beni, Río Mamoré, Río Ibaré , Cercado, 25 km N San Javier (14°24’S, 64°56’W) ; UMMZ 66433 (2), 215–331 mm, Beni, Río Beni, Lago Rogoagua (13°57’S, 66°58’W) ; UMSS 0 6962, 108 mm, Beni, Río Madeira, Arroyo Tres Cuchillas (10°49’23.02”S, 66°4’50.300” W) ; UMSS 0 6963, 121 mm, same locality as UMSS 06962 ; UMSS 0 6964, 174 mm, same locality as UMSS 06962 ; UMSS 0 6964, 177 mm, Beni, Río Madeira, Arroyo Tres Cuchillas (10°49’23.02”S, 66°4’50.30”W) ; UMSS 0 6965, 145 mm, same locality as UMSS 06962 ; UMSS 0 6966, 179 mm, same locality as UMSS 06962 ; UMSS 0 6969, 302 mm, same locality as UMSS 06962 ; UMSS 0 6970, 119 mm, same locality as UMSS 06962 ; UMSS 0 6977, 202 mm, Río Beni aff. Río Madeira (11°01’41.20”S, 66°5’58.80”W) . Peru: MUSM 60285 (holotype), 227 mm TL, Puno, Sandia, Río Candamo (13°31’S, 069°41’W) ; MUSM 60286 (2; paratypes), 101–121 mm TL, same locality as MUSM 60285 .

Figures

FIGURE 6. All five valid Gymnotus species from the Upper Madeira Basin, Bolivia and Peru. Scale bars = 10 mm TL. A. Gymnotus carapo madeirensis holotype, UMSS 06964, 178 mm TL. B. Gymnotus chaviro holotype, MUSM 33715, 233 mm TL. C. Gymnotus coropinae, MUSM 20264, 118 mm TL. D. Gymnotus eyra n. sp., INHS 37119, 178 mm TL. E. Gymnotus riberalta n. sp. holotype,CBF 10248, 199 mm TL.