Gymnotus paraguensis Albert and Crampton, 2003:34

Craig, Jack M., Malabarba, Luiz R., Crampton, William G. R. & Albert, James S., 2018, Revision of Banded Knifefishes of the Gymnotus carapo and G. tigre clades (Gymnotidae Gymnotiformes) from the Southern Neotropics, Zootaxa 4379 (1), pp. 47-73 : 70-72

Gymnotus paraguensis Albert and Crampton, 2003:34

Figure 16, Table 2

Material examined: Brazil: FMNH 108546 , 164 mm, Mato Grosso do Sul, Aquiduana, Brejo do Santa Sofia , Rio Novo (19°35’89”S, 056°20’47”W) ; MCP 13415, Santa Catarina, Rio Uruguai drainage, Rio Uruguai / Itá (27°17’60”S, 052°19’60”W) . Paraguay: NRM 42380, 240 mm, Canindeyú, Saltos da Guaira, Mulle Ytaipú, Río Paraná drainage (24°03’44”S, 054°18’W) ; NRM 42397, 171 mm, Central Province, Río Paraguay drainage, swamp close to Lago Ypacarai ; MNHNP 4169 , Department of Paraguay, Itapua, Capitan Meza Río de La Plata drainage, Río Paraná, Capitan Meza, Club de Caza y Pesca de Capitan Meza (26°57’44”S, 055°10’57”W) ; UMMZ 206155 (holotype), 222 mm, Department of Paraguay, Itapua, Río Paraná drainage, Arroyo Tembey , 7.4 km SW of San Rafael de Paraná (26°35’S, 055°34’W) ; UMMZ 240700 (paratype), 193 mm, same locality as UMMZ 206155 . Uruguay: ANSP uncat., Río Negro, Nuevo Berlín, Río de La Plata drainage, Río Uruguay , along shore near municipal pier (32°58’46”S, 058°3’48”W) .

Diagnosis. Gymnotus paraguensis differs from all sympatric members of the Gymnotus tigre clade ( G. inaequilabiatus ) on the following characters: 1, more precaudal vertebrae (PCV 32–35, median 34 vs. 45 in all specimens of G. inaequilabiatus ); 2, more ventral lateral-line rami (VLR 49055, median 50 vs. 23–38, median 32).

Description: Morphometric and meristic data in Table 1. Sexually monomorphic, including in breeding condition. Total length to 240 mm. Morphological maturity at roughly 110 mm. Scales rounded to slightly ovoid on anterior two thirds of body, ovoid on posterior one third. Gape large in mature specimens, to or beyond posterior nares. Mouth superior with lower jaw longer than upper, rictus decurved. Chin especially fleshy and protuberant with fleshy pad of electrosensitive organs overlying tip of snout and oral jaws. Anterior narial pore partially to entirely included within gape in narial fold. Anterior nares large, subequal to eye diameter. Circumorbital series ovoid. Ethmoid region broad between anterior nares, with rounded anterior margin. Eye position lateral, lower margin of eye dorsal or horizontal to rictus. Premaxilla with 12–13 teeth disposed in single row along outer margin, arrow-head shaped anteriorly, conical posteriorly. Straight 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 4–6 dentary teeth. Dentary with one row of 16–18 (median 17) teeth, none arrow-head shaped anteriorly. Posterodorsal and posteroventral dentary processes abut at midlength. Dentary posteroventral process shorter than posterodorsal, narrow distally. Dentary ventral margin lamella narrow, depth less than posterior process. Opercle dorsal margin straight to slightly convex. Dorsal opercular process lamellar or rugose, crest absent or small, posterior margin entirely smooth, without spines or processes. Preopercle with anteroventral notch, posterodorsal laterosensory ramus with two superficial pores, margin of medial shelf entire, median shelf large, more than one-half width of symplectic. Metapterygoid superior and inferior portions approximately equal in size, ascending process robust, long, base shorter than length, curved, tip simple. Interopercle dorsal margin ascending process broad. Subopercle dorsal margin concave. Retroarticular with an arched lamella posteriorly forming a small canal, posterior margin square. Anguloarticular process short, extending beyond ventral margin of dentary. Mandible long, extended, length greater than twice depth. Trigeminal nerve canals divided within the hyomandibula. Posterior lateral line fenestra not contacting posterodorsal margin of hyomandibula. 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 broad, more than two times width of supraorbital canal. Lateral ethmoid absent. Parietal rectangular, length less than width. Parasphenoid anteroventral portion robust, extending ventral to lateral margin of parasphenoid, posterior processes narrow. Prootic foraminae separate for cranial nerves Vp and V2–3 +VII. Adductor mandibula muscle undivided at insertion, intermuscular bones absent. All basibranchials unossified. Gill rakers not contacting gill bar. Pectoral with 17–21 (mode 19) rays, medial radial large. Mesocoracoid elongate, length more than four times width.

Cleithrum broad, ventral margin curved, anterior limb long, more than 1.8 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 long, with 32–35 (mode 34) precaudal vertebrae. Rib five robust along its entire extent, less than three times width of rib six. Hemal spines present. Displaced hemal spines absent. Length anal-fin pterygiophores equal to or longer than hemal spines. Anal fin with 214–390 (median 370) rays. Lateral line ventral rami 49–55 (median 50). Caudal appendage short, less one-half length of pectoral fin. Single hypaxial electric organ along entire ventral margin of body. Four rows of electroplates near caudal insertion of anal fin.

Color in Alcohol: Bands irregular in shape, width and color, on specimens and among individuals. Ground color tan to yellow. Obliquely-oriented, evenly-pigmented, chocolate-colored bands sharp margins on lateral surface from nape and to tip of caudal appendage (23–26 mode 24). Uniquely, three dark bands from either side meet at ventral midline between anus and anal-fin origin. Pale interband contrast similar along entire body axis. Head never banded, spotted, or blotched, dark grey dorsally grading to lighter grey ventrally. Numerous chromophores speckled over branchiostegal membranes and ventral surface of head. Pectoral-fin rays brown, interradial membranes hyaline. Anterior 40% of anal-fin brown, mid 40% black, posterior 20% translucent.