Revision of Banded Knifefishes of the Gymnotus carapo and G. tigre clades (Gymnotidae Gymnotiformes) from the Southern Neotropics
Craig, Jack M.
Malabarba, Luiz R.
Crampton, William G. R.
Albert, James S.
Zootaxa
2018
2018-02-13
4379
1
47
73
3HVMK
94173
Valenciennes, 1847
Valenciennes
1847
[151,712,1906,1933]
Actinopterygii
Gymnotidae
Gymnotus
GBIF
Animalia
Gymnotiformes
20
67
Chordata
species
inaequilabiatus
Materialexamined: Argentina: MACN 5979, 250mm, Rosario, Río La Plata(~ 32°56’S, 060°38’W); MLP 3353, 250mm, Misiones, Río Paraná(~ 26°49’S, 055°00’W); MNHN 4615 (neotype), 920 mm( 600 mmaccording to the original description, 850 mmaccording to the label), Argentina, Buenos Aires, Rio de La Plata (~30°40’S, 058°30’W according to MNHN database or ~34°37’S, 058°23’W). Brazil, Mato Grosso:LBP 12616, ~ 650 mm, Corumbá, Rio Paraguaidrainage, Rio Cuiabá(~ 18°09’S, 057°33’W). Brazil, Mato Grossodo Sul: MCP 15818, 535mm, Rio Paraguainear Cáceres; USNM 1643, 791mm, Rio Paraguaidrainage (~ 17°53’S, 057°29’W). Brazil, Rio Grande do Sul: MCP 6059(3), 173–355 mm, Iraí, Rio Uruguaidrainage, Sanga das Águas Frias, 100 mfrom Rio Uruguai( 27°12’00”S, 053°16’60”W); MCP 6956, 602mm, Rio Uruguaiat Santana Velha, near Uruguaiana(~ 29°45’S, 057°50’W); MCP19552 (3), 145–336 mm, Rosário do Sul, pool next to Olariain the floodplain along Rio Santa Maria, Northside of BR290 (30°14’16”, 054°53’33”W); MCP 31177, 560mm, Roque Gonzales, Rio Uruguaidrainage, Rio Ijuínear small hydroelectric power station ( PCH) Pirapó(~ 28°30’S, 055°10’W); MCP 39375, 550mm, same locality as MCP31177; UFRGS 14457, 498 mm, (~27°11’S, 053°06’W). Brazil, Santa Catarina: MCP 19044, 440mm, Itá, Rio Uruguai, Rio do Engano, road between Itá and Seara(27°08’60”S, 52°13’00”W); MCP 20683, 410mm, Itapiranga, Rio Uruguai, near Fortaleza( 27°11’42”S, 053°38’34”W). Brazil, São Paulo: MZUSP 22246(3), 130–282 mm, Represa do Boa, Corumbataí, Rio Paranádrainage, Rio Tietê(~ 21°46’S, 048°58’W); MZUSP 22862, 238mm, Corumbataí, Rio Paranádrainage, Rio Tietê, Lagoa Ponte Seca(~ 21°46’S, 048°58’W); MZUSP 46001, 998mm, Rio Paranádrainage, Porto Primavera(~ 22°31’S, 053°10’W).
Diagnosis. Gymnotus inaequilabiatusdiffers from all sympatric members of the Gymnotus tigreclade ( G. paraguensis) on the following characters: 1, more precaudal vertebrae ( 45 inall specimens vs. 32–35, median 34); 2, fewer ventral lateral-line rami (VLR 23–38, median 32 vs. 49–55, median 50). Gymnotus inaequilabiatusfurther differs from sympatric Gymnotusspecies on the following characters: 1, total length (max. 998 mmvs. max. 419 mmin G. c. australisand max. 305 mmin G. cuiathe next two largest species); 2, a color pattern characterized by 21–29, mode 22 obliquely-oriented, chocolate-colored bands in juveniles (< 400 mm), replaced in adults by large, irregular spots and blotches.
Description:Morphometric and meristic data in Table 1. Sexually monomorphic, including in breeding condition. Total length to 1 m.Morphological maturity at roughly 130 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 11 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 12–15 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 13–21 (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 45 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 23–38 (median 32). 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, spots and blotches irregular in shape, width and color, on specimens and among individuals. Ground color tan to yellow. In juveniles ( 250–400 mm), obliquely-oriented, 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 (21–29 mode 22). In adults, bands replaced by spots and blotches. 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. Anal-fin membrane with irregular broken horizontal stripes on posterior 20%.
1806563206
[151,1296,2008,2033]
MACN
Rosario
Argentina
-32.933334
Rio La Plata
1207
-60.633335
Material
20
67
MACN 5979, 250
1
1806563198
MLP
Argentina
21
68
-26.816668
Rio Parana
1240
-55.0
20
67
MLP 3353, 250
1
Misiones
1806563201
Corumba
Brazil
-18.15
Rio Cuiaba
1276
-57.55
Rio Paraguai
21
68
1
Mato Grosso
1806563196
MCP
Caceres
Brazil
Rio Paraguai
21
68
535
1
Mato Grosso do Sul
1806563204
[569,1350,294,319]
USNM
Paraguay
-17.883333
Rio Paraguai
1277
-57.483334
21
68
USNM 1643, 791
1
1806563200
MCP
Irai & Sanga das Aguas Frias
Brazil
100
-27.2
Rio Uruguai
Rio Uruguai
21
68
MCP 6059
1
Rio Grande do Sul
1806563213
MCP
Santana Velha & Uruguaiana
Uruguay
-29.75
Uruguai
1225
-57.833332
21
68
MCP 6956, 602
1
1806563199
MCP
Olaria & North
Uruguay
Rio Santa Maria
-54.8925
21
68
1
Rosario do Sul
1806563205
MCP, PCH
Roque Gonzales
Uruguay
-28.5
Pirapo
1232
-55.166668
Rio Ijui
21
68
560
1
1806563208
MCP
Roque Gonzales
Uruguay
-28.5
Pirapo
1232
-55.166668
Rio Ijui
21
68
550
1
1806563212
MCP
Ita
Brazil
Rio do Engano
-52.216667
Rio Uruguai
21
68
440
1
Santa Catarina
1806563211
[318,1349,580,605]
MCP
Itapiranga & Fortaleza
Uruguay
-27.195
Uruguai
20
-53.64278
21
68
410
1
1806563203
MZUSP
Corumbatai
Brazil
Represa do Boa
-21.766666
Rio Tiete
1262
-48.966667
Rio Parana
21
68
MZUSP 22246
1
Sao Paulo
1806563210
MZUSP
Corumbatai & Lagoa Ponte Seca
Brazil
-21.766666
Rio Tiete
1262
-48.966667
21
68
MZUSP 22862, 238
1
Parana
1806563202
[422,1408,687,712]
MZUSP
Porto Primavera
Brazil
-22.516666
Parana
1259
-53.166668
21
68
MZUSP 46001, 998
1
Parana