Gymnocorymbus ternetzi ( Boulenger, 1895 )

Benine, Ricardo C., Melo, Bruno F., Castro, Ricardo M. C. & Oliveira, Claudio, 2015, Taxonomic revision and molecular phylogeny of Gymnocorymbus Eigenmann, 1908 (Teleostei, Characiformes, Characidae), Zootaxa 3956 (1), pp. 1-28 : 14-17

Gymnocorymbus ternetzi ( Boulenger, 1895)

Fig. 11 , Table 4

Tetragonopterus ternetzi, Boulenger, 1895 . Type locality: “Descalvados, Matto Grosso”, ( Brazil).

Diagnosis. Gymnocorymbus ternetzi can be readily distinguished from all congeners by the presence of a dense field of dark chromatophores spread homogeneously over the posterior one half of the body vs. the lack of such pigmentation in all congeners; and by the shape of the first humeral mark (the absence of a wider densely pigmented region above the lateral line vs. the presence of such pigmented region in all congeners; Fig. 6 ). Gymnocorymbus ternetzi is also distinguished from all congeners by bearing premaxillary teeth in the inner row with three cusps vs. four to seven cusps ( Figs. 7–8 ). Gymnocorymbus ternetzi further differs from congeners, except G. flaviolimai , in having 5–6 vs. 2–4 scale series covering the anal-fin base and by bearing premaxillary teeth with three cusps vs. four to seven cusps ( Figs. 7–8 ). Gymnocorymbus ternetzi also differs from G. bondi and G. thayeri by its strongly convex distal margin of the anal fin vs. distal margin of the anal fin straight in G. bondi or slightly convex in G. thayeri ; and number of pelvic-fin rays (i,6 vs. i,7, respectively).

Description. Morphometric data for Gymnocorymbus ternetzi is summarized in Table 4 . Body deep. Relatively small-sized, largest specimen examined 53.1 mm SL. Greatest depth at origin of dorsal fin. Dorsal profile of head slightly concave. Dorsal profile of body convex from posterior tip of supraoccipital to end of dorsalfin base; slightly convex from rear of dorsal-fin base to end of adipose-base fin. Caudal peduncle profile slightly concave both dorsal and ventrally. Ventral profile of body convex from tip of lower jaw to caudal-peduncle origin. Prepelvic region slightly keeled medially but flattening proximate to pelvic-fin insertion. Postpelvic median keel extending from pelvic-fin insertion to anal-fin origin.

Supraoccipital process elongate; tip extends beyond vertical through posterior margin of opercle.

Mouth terminal. Maxillar extending beyond vertical through anterior margin of orbit nearly to vertical through middle of orbit. Premaxillary teeth in two rows. Outer row with 4 (77), 5* (32), or 6 (1) tricuspidate teeth, with middle cusp longest. Inner tooth row with 4 (18), 5* (84), or 6 (2) tricuspidate teeth, with middle cusp longest. One paralectotype (BMNH 1885.5.17.165) with six teeth in inner row of right premaxillar and five teeth in the inner row of left premaxillar. Maxillar lacking teeth (19) or with 1* (86) tricuspidate teeth. Dentary bearing five tri- to pentacuspidate teeth with central cusp usually longest, followed by one to three small conical or tricuspidate teeth.

Dorsal-fin rays ii, 9*. Pectoral-fin rays i,9,i (1), i,10,i (58), or i,11,i* (76). Tip of pectoral fin extends beyond midlength of adpressed pelvic fin. Adipose fin present. Pelvic-fin rays i,6. Tip of adpressed pelvic fin extends to first branched ray of anal fin. Anal-fin rays iv,32 (1), 34 (13), 35* (50), 36 (42), 37 (26), 38 (12), 39 (4), or 40 (1). Caudal fin forked with i,17,i principal caudal-fin rays.

Scales cycloid. Lateral line complete, 31 (6), 32 (53), 33 (66), 34* (21), or 35 (4). Scale rows between lateral line and dorsal-fin origin 7 (7), 8* (104), or 9 (7). Scale rows between lateral line and pelvic-fin origin 8* (79), or 9 (62). Circumpeduncular scale rows 12* (11), 13 (15), or 14 (18). Scale sheath along anal-fin base consisting of 5-6 scale series, extending across fin base.

First gill arch with 8 (28), 9 (28), or 10 (1) gill rakers on upper limb and 13 (33) or 14 (24) gill rakers on lower limb. Total vertebrae 32 (two c&s specimens, MZUSP 18720; 6 radiographed specimens, LBP 3762) or 33 (one radiographed specimen, LBP 3762). Supraneurals 4.

Color in alcohol. Overall coloration yellow tan. Homogeneous field of scattered dark chromatophores extending over posterior half of body. Dark chromatophores more densely concentrated along entire dorsal midline. Dense field of dark chromatophores extending over both lips, and dorsal third of maxilla. Infraorbital and opercular series with silvery pigmentation due to the presence of guanine. Vertical dark stripe as wide as eye crossing orbits. Two conspicuous vertical dark blotch in humeral region. Anterior blotch narrower than posterior. Anterior humeral blotch, located over second to fourth lateral-line scales and vertically extending over from five horizontal scale rows above lateral line to four to five horizontal scale rows below lateral line. Posterior humeral blotch located over ninth to twelfth lateral-line scales and vertically extending from six horizontal scale rows above lateral line to four to five horizontal scale rows below lateral line. The first humeral blotch roughly in the shape of an inverted isosceles triangle, located immediately posterior to the opercle, covering second to fourth lateral line scales and extending five scale rows above and three and a half scale rows below lateral line. Second humeral blotch liner mat with the first blotch ( Figs. 6 a and 11). Dorsal and anal fins homogenously darkly pigmented. Paired fins and caudal fin with few scattered dark chromatophores, more prominently along unbranched rays. Adipose fin densely dark pigmented, especially on its dorsal border ( Fig. 11 ).

Sexual dimorphism. Mature males bear a pair of small hooks per segment on the posterior branch of the first five to eight branched anal-fin rays.

Distribution. Gymnocorymbus ternetzi is known from the Río Paraguay basin as well as by isolated populations that were most likely introduced in the upper Rio Paraná and Rio Paraíba do Sul ( Fig. 9 ).

Remarks. According to the original description, Tetragonopterus ternetzi Boulenger, 1895 was described based on several specimens from Descalvados, Mato Grosso, Brazil. From the known type-material (five syntypes) deposited at the Natural History Museum (BMNH), we herein designate BMNH 1885.5.17.163 as the lectotype. The remaining four syntypes (BMNH 1885.5.17.164–167) accordingly become paralectotypes.

Material examined. Types: BMNH 1885.5.17.163, 1, lectotype (by present designation), 42.0 mm SL, Descalvados, Mato Grosso, Rio Paraguay, 16º46’S 57º44’W, C. Ternetz . BMNH 1885.5.17.164, 1, paralectotype (by present designation), 29.6 mm SL, same data as lectotype. BMNH 1885.5.17.165, 1, paralectotype (by present designation), 33.4 mm SL, same data as lectotype. BMNH 1885.5.17.166, 1, paralectotype (by present designation), 40.4 mm SL, same data as lectotype. BMNH 1885.5.17.167, 1, paralectotype (by present designation), 37.7 mm SL, same data as lectotype. Non-types: 187 specimens (21.2–53.1 mm SL). Brazil: Mato Grosso: ANSP 85396, 1, 46.5 mm SL, Rio Paraguay (no additional data). ANSP 101414, 1, 42.8 mm SL, Rio Paraguay (no additional data). LBP 3959, 1, 31.5 mm SL, Baía do Poço, Rio Cuiabá, Santo Antônio do Laverger, 15°54’03”S 56°01’17”W. LBP 5642, 1, 40.8 mm SL, Rio Coxipó, Rio Cuiabá, Cuiabá, 15°37’49.2”S 56°03’47.0”W. LBP 8443, 13, 21.2–45.3 m SL, Rio Paraguai, Cáceres, 16°03’13.6”S 57°48’31.8”W. LBP 8579, 1, 31.4 mm SL, Rio Paraguai, Barra do Bugres, 15°04’33.4”S 57°11’04.3”W. LBP 12143, 2, 33.5–35.5 mm SL, Rio Paraguay, Cáceres, 16°03’51.1”S 57°50’27.3”W. LBP 14005, 1, 35.0 mm SL, Rio Paraguay, Poconé, 17°49’26.7” S 57°31’03.0”W. FMNH 54656, 6, 37.9–41.0 mm SL, Rio Jauru. MZUSP 18720, 8, 2 c&s, 42.7–53.1 mm SL, Santo Antônio do Leverger, Ranchão da Lagoa, 15º56’S 56º07’W. MZUSP 18753, 4, 38.2–40.3 mm SL, Descalvados, Rio Paraguay, 16º46’S 57º44’W. MZUSP 27097, 11, 40.2–51.6 mm SL, Poconé, Campo do Jofre, Rio Cuiabá, Rio Paraguay, 17º18’S 56º50’W. MZUSP 28084, 8, 36.0– 41.8 mm SL, Porto Esperidião, Rio Jauru, 15º50’S 58º27’W. MZUSP 35911, 1, 45.6 mm SL, Itiquira, lagoons between Rio Piquiri and Rio Itiquira, Fazenda Santo Antônio do Paraíso. MZUSP 51019, 5, 35.5–42.7 mm SL, Poconé, Campo do Jofre, Rio Cuiabá, Rio Paraguay, 17º18’S 56º50’W. Mato Grosso do Sul: LBP 30, 17, 26.8–40.6 mm SL, Rio Miranda, Rio Paraguay, Corumbá, 19°34,630’S 57°01,123’W. LBP 3737, 9, 26.5–33.5 mm SL, marginal lagoon of Rio Negro, Rio Paraguay, Aquidauana, 19°34’54.6”S 56°15’16.5”W. LBP 3762, 32, 32.4–38.2 mm SL, marginal lagoon of Rio Negro, upper Rio Paraguay, Aquidauana, 19°34’02.3”S 56°14’09.1”W. LBP 3797, 3, 31.2–38.3 mm SL, marginal lagoon of Rio Negro, upper Rio Paraguay basin, Aquidauana, 19°34’02.3”S 56°14’09.1”W. LBP 9827, 5, 29.5– 31.3 mm SL, Rio Miranda, Miranda, 19°34’58.3”S 57°01’18.9”W. FMNH 71035, 3, 37.9–41.9 mm SL, Conceição, Rio Paraguay, 21º45’S 57º05’W. MZUSP 36420, 5, 28.5–46.6 mm SL, Corumbá, Nhecolândia, Fazenda Nhumirim, 18º59’S 56º39’W. São Paulo: LBP 4966, 5, 36.2–42.5 mm SL, Lagoa do Diogo, Rio Mogi- Guaçu, upper Rio Paraná basin, Luis Antônio, 21°37’26.7”S 47°48’22.6”W. LBP 5078, 13, 37.8–46.0 mm SL, Lagoa do Diogo, Rio Mogi-Guaçu, upper Rio Paraná, Luis Antônio, 21°37’26.7”S 47°48’22.6”W. LBP 5159, 5, 32.0– 38.6 mm SL, marginal lagoon of Rio Tamanduá, Rio Mogi-Guaçu, upper Rio Paraná, Cravinhos, 21°20’48.9”S 47°37’59.4”W. LBP 17712, 2, 29.6–29.7 mm SL, marginal lagoon of Rio Mogi-Guaçu, upper Rio Paraná, Pirassununga, 21°52’32.9”S 47°24’34.7”W. LIRP 367, 20, 32.2–45.9 mm SL, Luís Antônio, Reserva de Jataí, Lagoa do Diogo, Rio Mogi-Guaçu, 21º37’26”S 47º48’28”W. LIRP 3490, 1, 23.6 mm SL, Miguelópolis, Córrego do Matão, Rio Sapucaí, Rio Grande, 20°11’50.0”S 48°13’43.0”W. Paraguay: FMNH 15027, 1, 38.7 mm SL, Departamento Central, Distrito de Areguá, Lake Ypacaraí, 25º18’S 57º22’W. FMNH 54655, 3, 38.5–41.0 mm SL, Departamento Central, Distrito de Areguá, Lake Ypacaraí, Río Areguá, 25º18’S 57º22’W.

Figures

FIGURE 6. Graphical representation of the differences in the pattern of the humeral mark pigmentation in (a) Gymnocorymbus ternetzi and (b) G. bondi and G. thayeri.

FIGURE 7. Representation of the posterior view of the premaxillar showing (a) pentacuspidate to heptacuspidate teeth of Gymnocorymbus thayeri, MZUSP 6280, 40.3 mm SL; and (b) tricuspidate teeth of G. ternetzi, MZUSP 18720, 39.4 mm SL.

FIGURE 8. Anterior view of a premaxillary tooth of (a) Gymnocorymbus flaviolimai, INPA 11098, 46.7 mm SL, relatively smaller, pentacuspidate tooth; (b) G. ternetzi, LIRP 367, 37.7 mm SL, tricuspidate tooth; and (c) G. thayeri, LBP 17756, 40.2 mm SL, relatively larger, pentacuspidate tooth. Scale bar = 0.25 mm.

FIGURE 9. Distribution map showing collecting localities of examined specimens of Gymnocorymbus bondi (white circles), G. flaviolimai (red circles), G. ternetzi (blue circles) and G. thayeri (yellow circles). White lines represent country boundaries.

FIGURE 11. Gymnocorymbus ternetzi. a) Lectotype of Tetragonopterus ternetzi, BMNH 1885.5. 17.163, 42.0 mm SL, Descalvados, Mato Grosso, Rio Paraguay, Brazil, photo by Sandra J. Raredon; b) Gymnocorymbus ternetzi, LBP 3762, 38.2 mm SL, Aquidauana, Mato Grosso do Sul, Rio Paraguay, Brazil.

Tables

TABLE 4. Morphometric data for Gymnocorymbus ternetzi; N includes lectotype.

	N	Lectotype	Range	Mean
Standard length (mm)	160	42.0	21.2–53.1	–
Percentage of standard length
Greatest depth	160	56.7	51.0–67.2	59.6
Snout to dorsal-fin origin	155	49.7	41.9–59.3	54.2
Snout to pectoral-fin origin	160	32.4	24.7–38.3	32.0
Snout to pelvic-fin origin	160	47.9	46.3–56.7	49.6
Snout to anal-fin origin	160	58.0	55.3–70.3	61.1
Caudal peduncle depth	160	10.8	7.6–12.8	10.8
Caudal peduncle length	160	9.7	5.8–11.5	8.0
Pectoral-fin length	160	22.2	19.0–29.6	25.7
Pelvic-fin length	160	16.1	11.2–20.2	17.0
Dorsal-fin length	155	–	25.4–36.9	32.5
Dorsal-fin base	160	18.7	13.8–22.2	18.9
Anal-fin length	160	17.3	17.3–31.5	25.0
Anal-fin base	160	53.4	46.7–63.2	53.0
Eye to dorsal fin origin	160	39.2	30.4–48.1	41.5
Head length	160	29.0	23.0–34.3	29.9
Head depth	160	22.7	18.5–32.1	24.4
Percentage of head length
Snout length	160	24.4	17.2–30.8	24.6
Upper jaw length	160	44.7	39.8–49.6	44.7
Horizontal orbital diameter	160	40.5	31.7–48.9	41.2
Least interorbital width	160	32.8	29.0–40.5	33.3