Gephyrocharax sinuensis Dahl, 1964

Vanegas-Ríos, James A., 2016, Taxonomic review of the Neotropical genus Gephyrocharax Eigenmann, 1912 (Characiformes, Characidae, Stevardiinae), Zootaxa 4100 (1) : 60-65

Gephyrocharax sinuensis Dahl, 1964

( Figs. 25–27 )

Gephyrocharax sinuensis Dahl in Dahl & Medem, 1964: 64 –66, unnumbered fig. on page 64 [original description, designation

of type material without catalogue number, holotype ICNMHN lost, type locality: “de Esmeraldas, Alto Sinú” ( Colombia:

upper Sinú River in Esmeraldas]. Dahl, 1971: 134–135 unumbered fig. on page 135 [key, distributional data]. Mojica,

1999: 557 [listed from Colombia, data compilation]. Weitzman, 2003: 225 [catalogue]. Maldonado-Ocampo, Vari &

Usma, 2008: 180 [listed from Colombia]. Álvarez-León, Orozco-Rey, Páramo-Fonseca & Restrepo-Santamaría, 2013: 101

[listed from Colombia]. Bonilla-Rivero & López-Rojas, 2013: 489, fig. 1 [distribution map]. Vanegas-Ríos, Azpelicueta,

Mirande, Gonzales, 2013: 283 [examined material]. Thomaz, Arcila, Ortí & Malabarba, 2015: Add. File 5 [tentative

classification].

Diagnosis. Gephyrocharax sinuensis is distinguished from its congeners by having the unbranched pelvic-fin ray hypertrophied and distally curved in adult males (vs. this pelvic-fin ray straight along its length, not hypertrophied, similar to remaining rays) and an intense pigmentation of dark chromatophores extending around the pelvic-fin origin in adult males (vs. absence of this pigmentation pattern, usually this area with variably present scattered distributed chromatophores, except in G. caucanus and G. valencia ). From G. caucanus , G. intermedius , G. m a r t a e, G. valencia , and G. venezuelae , the species can be further differentiated by the greater pelvic-fin length of males (17.1–26.8 % SL vs. 12.2–17.5 % SL). The presence of a humeral blotch (vs. absence of this blotch) differentiates G. sinuensis from G. caucanus , G. valencia , and G. m a r t a e, and the lack of bony hooks on the pectoral-fin rays in adult males (vs. presence of hooks on this fin) distinguishes it from G. melanocheir and G. t o r re s i. Gephyrocharax sinuensis also differs from G. t o r re s i and G. valencia by the possession of a rhinosphenoid bone (vs. absence of this bone) and from G. atracaudatus , G. chocoensis , G. intermedius , G. major , and G. venezuelae by the externally developed urogenital papillae in adult females (vs. this papillae not developed externally). From G. m el a n o c h ei r, G. torresi , G. v a l e n ci a, and G. venezuelae it is distinguished by having the pouch scale of adult males posteriorly extending beyond the vertical through the distal tip of the second ventral procurrent ray of caudal fin (vs. pouch scale not extending beyond this vertical).

Description. Morphometric data in Table 7 . Largest male 35.1 mm SL, largest female 40.8 mm SL. Body laterally compressed, with maximum depth at vertical through midpoint between pelvic- and anal-fin origins. Dorsal profile of head somewhat convex from margin of upper lip to tip of supraoccipital spine. Dorsal profile of body slightly convex from that point to dorsal-fin origin, slanting posteroventrally along dorsal-fin base, and straight from posteriormost dorsal-fin ray to caudal peduncle ( Fig. 25 ). Ventral profile of body convex from tip of dentary to vertical crossing anal-fin origin, and slanting posterodorsally and straight from this point to caudal peduncle origin. Anterior fontanel present, sometimes reduced to narrow or medium-sized opening anterior to epiphyseal bar. Anterior nostril rounded and separated by skin fold from larger posterior nostril. Groove with at least three rows of neuromasts extending from half-length between posterior pore of nasal bone and nostrils to posterior portion of frontals. Small groove with few neuromasts between nostrils and nasal bones.

Characters Males Females and unsexed juveniles ......continued on the next page Characters Males Females and unsexed juveniles Mouth superior, lower jaw projecting anterior to tip of upper jaw. Premaxilla with two rows of teeth. Outer row with 1 (1), 2 (4), 3 (10), 4* (36), or 5 (5) teeth, usually tricuspid. Inner row with 4 (35), 5* (21), or 6 (1) teeth; symphyseal tooth and remaining teeth tri- to pentacuspid. Maxilla rarely toothless (2), usually with 1* (45) or 2 (9) teeth, tri- to pentacuspid (often tetracuspid) ( Fig. 26 A). Maxilla posteriorly reaching vertical through anterior onethird of eye. Dentary with 9 (1), 10 (4), 11 (16), 12 (17), 13 (6), 14* (6), or 15 (2) teeth; three anteriormost teeth larger, tetra- or pentacuspid, followed by one median-sized tooth pentacuspid, and 5 (1), 6 (1), 7 (16), 8 (17), 9 (6), 10* (6), or 11 (2) smaller conical to tricuspid teeth ( Fig. 26 B).

Dorsal-fin rays ii,8* (55) or 9 (2). Nine* proximal pterygiophores on dorsal fin (1 rad, 2 c&s). Dorsal-fin origin located at vertical between anal-fin rays 6–11. Adipose-fin origin located at vertical through base of posteriormost anal-fin ray. Anal-fin rays iii (1), iv (39), or v* (17), 22 (1), 24 (4), 25 (9), 26 (18), 27 (15), or 28* (8). Twenty-six to 30 proximal pterygiophores on anal fin (1 rad, 2 c&s). Anal-fin origin closer to origin of hypural joint than to snout tip. Pectoral-fin rays i,8 (11), 9* (32), or 10 (13). Pectoral-fin distal tip posteriorly reaching onequarter to one-half of pelvic-fin length. Pelvic-fin rays i,6 (56) or i,7 (1). Pelvic-fin origin located at vertical between pored lateral-line scales 8–10 and anterior to body midlength. Caudal fin forked with 10/9 principal rays in all specimens.

Scales cycloid, with numerous radii along posterior margin. Lateral line complete, pored scales 37 (1), 38 (10), 39 (10), 40 (20), 41 (9), 42* (5), or 43 (1). Terminal lateral-line tube present, atypically absent in two males. Predorsal scales 16 (1), 17 (12), 18* (11), 19 (16), 20 (11), or 21 (5). Scale rows between dorsal fin and lateral line 5* (15) or 6 (39). Scale rows between lateral line and anal fin 4* (19) or 5 (37). Scale rows between lateral line and pelvic fin 3 (3), 4* (32), or 5 (21). Circumpeduncular scales 14* (18), 15 (30), or 16 (4). One row of 11 (7), 12 (1), 13 (3), 14* (12), 15 (9), 16 (9), 17 (4), 18 (1), or 19 (1) scales forming sheath along anal-fin base. Total number of vertebrae 39 (2) or 41* (1); 16* (3) precaudal and 23 (2) or 25* (1) caudal (1 rad, 2 c&s). Gill-rakers on dorsal limb of first branchial arch 5* (3), 6 (36), 7 (9), or 8 (1); ventral limb with 11* (19), 12 (27), or 13 (3).

Color in alcohol. Ground color pale brown, darker along mid-dorsal line, slightly lighter ventrally. Minute scattered dark chromatophores covering body, less so or absent on lateral and ventral regions of abdomen and ventral region of caudal peduncle. Dark midlateral stripe diffuse, extending from vertical through midpoint between anal and pelvic-fin origins to posterior region of caudal peduncle. Dark chromatophores present along myosepta between lateral line and upper portion of anal fin. Dark humeral blotch vertically elongate. Dark blotch on caudal peduncle, horizontally elongate, and extending from posterior region of peduncle across interradialis muscles to midlength of middle caudal-fin rays. Dorsal fin light gray, with scattered dark chromatophores on rays and membranes. Anal fin light gray, with dark chromatophores mostly concentrated on interradial membranes. Caudal fin light gray, with scattered dark chromatophores on rays and membranes. Pectoral and pelvic fins light gray, with dark chromatophores mainly on rays. Head darker dorsally than ventrally. Dark chromatophores more concentrated on opercle and on margins of infraorbitals bordering eye. Premaxilla, anterior portion of maxilla, dentary, and lips with concentrated dark chromatophores. Variations in color pattern between males and females described under sexual dimorphism.

Sexual dimorphism. Males with bony hooks on anal-, caudal-, and pelvic-fin rays. Caudal fin with short, slender, anterodorsally oriented hooks, especially on branched portions of rays 13–18 ( Fig. 26 C). Pelvic-fin rays, except unbranched and innermost rays, with short, slender, anteroventrally oriented hooks on nearly entire length of rays; hooks usually paired or one per segment, fewer and unpaired on bases of rays. Anal fin with slender, anterolaterally placed hooks with broad bases; from 2 to 19 pairs per ray located from posteriormost unbranched ray and up to eight anterior branched rays (larger hooks on middle rays of this range). In adult males, usually posteriormost unbranched anal-fin ray up to 12 or 13 anterior branched rays slightly longer than remaining rays, resulting in convex-shaped margin. In females, anal-fin rays gradually decreasing in length from anteriormost branched ray to posteriormost branched ray, resulting in concave or straight anal-fin margin. Anal-fin base of adult males slightly concave or curved along its midlength, this base straight in females. Unbranched pelvic-fin ray of adult males hypertrophied, longer and thickener than other rays; distal portion somewhat curved and expanded ( Fig. 25 ). Innermost pelvic-fin ray often slightly longer than other rays except unbranched ray. Females not having this unbranched ray as hypertrophied as males, but usually slightly longer and thicker than other pelvic-fin rays. Adult females with external, ventrally oriented urogenital papillae.

Adult males with dark pigmentation extending mainly ventrally from urogenital pore to vertical through posterior half of pectoral fin; more intense around and anterior to pelvic-fin origin. Mature males with hypertrophied scale forming pouch on lower caudal-fin lobe and with ventral procurrent rays 2 and 3 forming spurshaped structure. Scarce small aggregations of apparent glandular tissue located on caudal-fin rays and medially to pouch scale. First ventral procurrent ray with moderate concavity on its ventral margin ( Fig. 26 C). Second ventral procurrent ray somewhat longer than third ray, posteriorly reaching midlength of first ventral procurrent ray, and flattened in sagittal plane, especially on its posterior portion. Posterior portion of third ventral procurrent ray weakly developed laterally. Pouch scale with 21–43 radii, usually between caudal-fin ray 16 and third ventral procurrent ray. Posteroventral pouch-scale lobe well developed, extending posteriorly along third ventral procurrent ray ( Figs. 26 C–D). Dorsal surface of pouch scale attached via soft tissue (apparently connective) to caudal-fin rays 11–14. Posterior margin of pouch scale located between caudal-fin ray 14 and third ventral procurrent ray. Four scales in vertical series situated ventral to terminal lateral-line scale, overlapping posterior portion of pouch scale. Dorsal margin of pouch scale slightly convex. Females with large scale with 21 (2), 22 (1), 23 (3), or 26 (1) radii on lower caudal-fin lobe.

Mature males with gill gland, formed by fusion of 7 (1), 10 (2), 11 (2), 12 (3), 13 (4), 14 (1), 15* (2), 16 (2), or 17 (1) anterior gill filaments of ventral limb of first gill arch. Total number of ventral limb gill filaments 21 (1), 22 (1), 23 (1), 24* (6), 25 (2), 26 (5), or 27 (1). Gill-gland length 3.0–7.5 % SL (mean = 6.0 % SL), 6.9* % SL. Regression comparisons of morphometric data by sex with more pronounced differences for pelvic-fin length (higher values in males than in females) in larger specimens as function of SL ( Fig. 27 ).

Distribution. Gephyrocharax sinuensis is only known from the Sinú River basin in Colombia ( Fig. 1 ).

Remarks. The holotype of G. sinuensis (ICNMHN with unknown catalogue number) is considered lost. Cala (1987) commented that George Dahl was retired as curator of the fish collection at ICN (Instituto de Ciencias Naturales, Colombia) in 1961 and then he moved to INDERENA (= CVM, Cartagena), where the type specimens designated by Dahl were deposited. Later on, Cala (1987) affirmed that he transferred to ICN these types or at least the specimens that could be recovered (several types were destroyed). According to this, the holotype of G. sinuensis was not cited anymore in the last version of the types catalogue from ICNMNH ( Mojica & Castellanos 2007). After some personal visits made to ICNMNH, the holotype neither could be found. Therefore, a neotype is designated (ICNMHN 18999) based on the article 75.3.4 of the ICZN (1999). This specimen is an adult male selected from the 78 paratypes (ICNMHN 749) examined for G. s i n u e n s i s, following the recommendation 75A of the ICZN (1999). The paratypes of G. sinuensis are relatively in a good condition but slightly depigmented. As the paratypes were loaned to Stanley H. Weitzman in 1984, the neotype is currently located at NMNH (USNM) while all the material is returned to ICNMHN.

Material examined. All specimens from Colombia, Córdoba, Sinú River basin: CAR 403, 7, 30.5–36.0 mm SL (2 c&s 35.1–35.9 mm SL), Tierra Alta, La Oscura creek, tributary of Tai River, approximately 8°0'15.97"N 76°7'27.44"W 86 m a. s. l. CAR 446, 5, 28.2–34.0 mm SL, Tierra Alta, Tigre River upstream of El Carmen creek, approximately 8°15'2.90"N 75°58'9.79"W 36 m a. s. l. ICNMHN 749, 78 paratypes, 16.1–40.8 mm SL, collected with the neotype. Dahl. ICNMHN 6843, 10, 30.7–39.6 mm SL, Sinú River, approximately 7°48'27.83"N 76°19'52.52"W 253 m a. s. l. (coordinates estimated for map of distribution). ICNMHN 6915, 13, 24.0– 34.2 mm SL, Sinú River, approximately 7°48'27.83"N 76°19'52.52"W 253 m a. s. l. ICNMHN 18999 (previously ICNMHN 749), neotype of Gephyrocharax sinuensis by present designation, 32.1 mm SL (rad), male, upper Sinú River, approximately 7°49'17.73"N 76°17'32.05"W 196 m a. s. l. (in Dahl’s original description cited as Sinú between Manso and Chobogadó rivers). NRM 36890, 2, 32.9–34.1 mm SL, Tierra Alta, unnamed creek emptying the about 3 km downstream of Urrá Hidropower station, approximately 8°2'59.07"N 76°10'13.62"W 68 m a. s. l. NRM 16275, 2, 30.4–33.1 mm SL, Tierra Alta, Manso River, tributary of Sinú River, approximately 7°39'53.06"N 76°9'43.64"W 182 m a. s. l. NRM 39614, 11, 20.2–32.5 mm SL, Tierra Alta, unnamed creek emptying about 3 km downstream Urrá Hydropower station, approximately 8°3'4.98"N 76°10'3.64"W 67 m a. s. l.

Figures

FIGURE 1. Geographic distribution of Trans-Andean species of Gephyrocharax occurring west from eastern versant of Andean Cordillera in northwestern South America to southern Central America.

FIGURE 25. Gephyrocharax sinuensis, (A) male, neotype by present designation, 32.1 mm SL, ICNMHN 18999; (B) male, 34.0 mm SL, CAR 446; (C) female, 36.0 mm SL, CAR 403. White arrows indicate urogenital papillae and unbranched hypertrophied pelvic-fin ray.

FIGURE 26. Gephyrocharax sinuensis, (A – B) upper and lower jaws, female, 35.9 mm SL, CAR 403; (C – D) detail of lower caudal skeleton and associated pouch scale, male, 35.1 mm SL, CAR 403. Anguloarticular: aa, dentary: dt, maxilla: mx, premaxilla: pm, pouch scale: ps, posteroventral lobe: pvl, principal caudal-fin ray: pcr, retroarticular: ra, spur-shaped structure: sss, ventral procurrent ray: vpr. Lateral view, left side. Scale = 1 mm.

FIGURE 27. Regression plot by sex of pelvic-fin length as function of SL for Gephyrocharax sinuensis (females, r = 0.89, r 2 = 0.80, ɑ = 0, β = 0.180, n = 31; males, r = 0.81, r 2 = 0.65, ɑ = 0, β = 0.216, n = 23).

Tables

TABLE 7. Morphometric data of neotype (A) by present designation (ICNMHN 18999), paratypes, and other examined specimens of Gephyrocharax sinuensis. Ranges of males including neotype values. M = mean; SD = standard deviation.

	Neotype	n	Range	M	SD	n	Range	M	SD
Standard length (mm)	32.1	36	24.2–35.1	30.3	2.5	61	20.2–40.8	30.3	4.8
Percentages of standard length:
Depth at dorsal-fin origin	32.1	23	28.3–36.3	32.4	1.9	34	27.2–36.0	32.0	2.5
Snout to dorsal-fin origin	65.3	23	63.7–67.5	66.4	0.8	34	64.2–71.0	66.5	1.4
Snout to pectoral-fin origin	27.0	23	25.6–29.4	28.0	1.0	34	26.0–29.3	27.5	0.7
Snout to pelvic-fin origin	44.3	23	41.1–47.8	44.4	1.5	34	43.5–48.8	45.5	1.3
Snout to anal-fin origin	56.0	23	55.9–61.5	58.8	1.8	34	57.9–63.3	60.5	1.2
Dorsal fin to pectoral fin length	47.7	23	46.9–50.7	49.0	1.1	34	46.0–53.7	49.8	1.9
Dorsal fin to adipose fin length	26.2	23	22.9–26.4	25.2	1.0	34	22.6–27.5	25.0	1.2