Gephyrocharax chocoensis Eigenmann 1912
Creators: name: Vanegas-Ríos, James A.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Characiformes
Characidae
Gephyrocharax
Gephyrocharax chocoensis

description: Gephyrocharax chocoensis Eigenmann, 1912
(Figs. 10–13)
Gephyrocharax chocoensis Eigenmann, 1912: 23 –24 [designated as type species of genus, original description, holotype FMNH 56016 (CM 4806), type locality: “Istmina” (= Colombia: Chocó, San Juan River basin, Istmina)]. Eigenmann, 1914: 41 [listed, key]. Meek & Hildebrand, 1916: 289 [compared with G. intermedius]. Myers in Eigenmann & Myers, 1929: 477 –479, pl. 53, fig. 1, pl. 97, fig. 3 [key, redescription]. Schultz, 1944: 323 [key]. Weitzman & Fink, 1985: 103 [examined material]. Román-Valencia, 1990: 206, [listed from Atrato River]. Burns, Weitzman, Grier & Menezes, 1995: 133 –135 [spermatozoid morphology, evidence of insemination]. Mojica, 1999: 557 [listed from Colombia, data compilation]. Bushmann, Burns & Weitzman, 2002: 189 [gill gland morphology]. Weitzman, 2003: 224 [catalogue]. Mojica, Usma & Galvis, 2004: [listed from Chocó, recorded for Baudó River but not substantiated by specimens]. Maldonado-Ocampo, Villa-Navarro, Ortega-Lara, Prada-Pedreros, Jaramillo, Claro, Usma, Rivas, Chaverra, Cuesta & García-Melo, 2006: 149 [listed from Atrato River]. Maldonado-Ocampo, Vari & Usma, 2008: 180 [listed from Colombia]. Maldonado-Ocampo, Usma, Villa-Navarro, Ortega-Lara, Prada-Pedreros, Jaramillo, Claro, Arango, Rivas & Sánchez, 2012: 28, 145–146, [listed from Chocó, color in life, recorded for Baudó River but not substantiated by specimens]. 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: 282 [examined material]. Thomaz, Arcila, Ortí & Malabarba, 2015: 5, 10, table 2, fig. 5, Add. Files 2, 5 [comments on insemination strategy, phylogenetic relationships, placed in Stevardiinae, Stevardiini, sampled specimens].
Gephyrocharax chocoënsis. Eigenmann, 1922: 155 [catalogue, name misspelled].
Gephyrocharax cf. sinuensis. Román-Valencia & Acero, 1992: 122, table 5 [in part, misidentified].
Diagnosis. Gephyrocharax chocoensis differs from its congeners by having the posteriormost section of hypaxialis and epaxialis muscles of caudal peduncle well developed and laterally extending over flexor ventralis in adult males (vs. posteriormost section of these muscles reduced, nearly absent, and not laterally extending over flexor ventralis, except in G. major) and by not having the distal portion of the fourth ventral procurrent ray of caudal fin in adult males flattened in sagittal plane (vs. distal portion strongly flattened sagittally, except in G. m a j o r and G. valencia). The species is also distinguished from most congeners by the position and extent of the caudal peduncle blotch which is more concentrated on the middle caudal-fin rays than on caudal peduncle, reaching the midlength of those rays (vs. caudal peduncle blotch situated more on caudal peduncle than on middle caudal-fin rays, not reaching midlength of these rays, except in G. sinuensis and G. m a r t a e) and the dorsal margin of the pouch scale in adult males located on the caudal-fin ray 12 or ventral to it (vs. dorsal margin of pouch scale located dorsal to this ray, except in G. atracaudatus and G. venezuelae). The possession of a lobe on the posteroventral margin of the pouch scale in adult males differentiates Gephyrocharax chocoensis from G. atracaudatus, G. intermedius, and G. major. Additionally, Gephyrocharax chocoensis is distinguished from G. major by the absence of accessory scales on the pouch scale of adult males (vs. presence of these scales) and by having the second and third ventral procurrent rays strongly curved dorsally and ventrally in adult males (vs. second and third rays straight). It can be distinguished from G. melanocheir, G. t o r re s i, and G. valencia by the possession of a terminal lateral-line tube between caudal-fin rays 10 and 11 (vs. absence of this tube). Gephyrocharax chocoensis differs from G. caucanus, G. sinuensis, and G. valencia by not presenting dark pigmentation around pelvic-fin origin in adult males (vs. presence of this pigmentation) and from G. martae by the snout to pectoral-fin length (24.5–28.6 % SL vs. 20.7 % SL).
Description. Morphometric data in Table 3. Largest male 48.2 mm SL, largest female 52.1 mm SL. Body laterally compressed, with maximum depth at vertical through midpoint between pelvic- and anal-fin origins or slightly anterior to anal-fin origin. 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, straight from posteriormost dorsal-fin ray to caudal peduncle (Fig. 10). Ventral profile of body convex from tip of dentary to vertical through distal half of pectoral fin, straight or slightly concave from this point to anal-fin origin, straight and slanting posterodorsally along anal-fin base. Anterior fontanel absent or reduced to narrow opening anterior to epiphyseal bar. Anterior nostril rounded, 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.
Caracteres Males Females and unsexed juveniles ......continued on the next page
Caracteres Males Females and unsexed juveniles Mouth superior, lower jaw projecting slightly anterior to tip of upper jaw. Premaxilla with two rows of teeth. Outer row with 2 (2), 3 (18), 4* (65), or 5 (2) teeth; usually tricuspid, rarely conical or bicuspid teeth. Inner row with 4 (70) or 5* (19) teeth; symphyseal tooth tetracuspid, remaining teeth pentacuspid (rarely tetracuspid). Maxilla rarely toothless (1), usually with 1* (74) or 2 (14) teeth; tri- to pentacuspid (Fig. 11 A), larger specimens with greater number of cusps. Maxilla posteriorly reaching vertical through anterior one-third of eye. Dentary with 9 (1), 10 (2), 11 (15), 12 (27), 13 (26), 14 (4), 15 (1), 16 (1), or 17 (1) teeth; three anteriormost teeth larger, tetra- to pentacuspid, followed by one median-sized tooth usually tri- to pentacuspid, and 5 (1), 6 (1), 7 (15), 8 (27), 9 (26), 10 (4), 11 (1), 12 (1), or 13 (1) smaller conical to tricuspid teeth (Fig. 11 B).
Dorsal-fin rays ii,7 (2), 8* (86), or 9 (1). Nine* proximal pterygiophores on dorsal fin (4 rad, 6 c&s). Dorsalfin origin located at vertical between anal-fin rays 6–10. Adipose-fin origin located at vertical through base of posteriormost anal-fin ray. Anal-fin rays iv* (39), v (49), or vi (6), 24 (1), 25 (6), 26 (17), 27 (28), 28* (15), 29 (16), 30 (6), or 31 (1). Twenty-seven to 31 proximal pterygiophores on anal fin (4 rad, 6 c&s). Anal-fin origin closer to origin of hypural joint than to snout tip. Pectoral-fin rays i,8 (1), 9 (45), 10* (40), or 11 (1). Pectoral-fin distal tip posteriorly reaching one-quarter to one-half of pelvic-fin length. Pelvic-fin rays i,6 (7) or 7* (81) (one atypical specimen with 8 branched rays) (Fig. 6). Pelvic-fin origin located at vertical between pored lateral-line scales 10–11 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 (22), 39 (18), 40 (23), 41* (19), 42 (5), or 43 (1). Terminal lateral-line tube present. Predorsal scales 17 (22), 18 (27), 19 (28), 20* (12), or 21 (1). Scale rows between dorsal fin and lateral line 5 (31) or 6* (59). Scale rows between lateral line and anal fin 4 (58) or 5* (32). Scale rows between lateral line and pelvic fin 3 (2), 4 (78), or 5* (10). Circumpeduncular scales 13 (24), 14* (56), or 15 (6). One row (one specimen with two rows) of 11 (2), 12 (4), 13 (5), 14 (9), 15 (15), 16 (12), 17 (15), 18 (3), 19 (5), 21 (1), or 22 (1) scales forming sheath along anal-fin base. Total number of vertebrae 39 (3) or 40* (6); 16* (9) precaudal and 23 (3) or 24* (6) caudal (4 rad, 6 c&s). Gill-rakers on dorsal limb of first branchial arch 5* (8), 6 (57), or 7 (6); ventral limb with 11* (37), 12 (33), or 13 (2).
Color in alcohol. Ground color pale yellowish, darker along mid-dorsal line, slightly lighter ventrally. Minute dark chromatophores covering body except on lateral and ventral regions of abdomen and caudal peduncle. Dark midlateral stripe diffuse (silvery in specimens retaining guanine: IMCN 4830), extending from humeral region or at vertical through pelvic-fin origin to caudal peduncle. Dark chromatophores present along myosepta between lateral line and upper portion of anal fin. Humeral blotch absent (populations from San Juan River basin) or, when present (populations from Atrato and León rivers basins), vertically elongate and somewhat diffuse. Dark blotch on caudal peduncle, roughly ovoid, horizontally elongate, extending from posterior region of peduncle across interradialis muscles to midlength of middle caudal-fin rays. Dorsal fin light gray or faint yellow, with scattered dark chromatophores on rays and membranes. Anal fin light gray, with dark chromatophores concentrated on interradial membranes. Caudal fin light gray, with dark chromatophores mostly concentrated on rays. Pectoral and pelvic fins light gray, chromatophores absent or reduced on rays. Head darker dorsally than ventrally. Chromatophores absent or reduced on opercle and infraorbitals. Premaxilla, anterior portion of maxilla, dentary, and lips with faint concentrated dark chromatophores. Variations in color pattern between males and females not observed.
Color in life. Based on specimens from IMCN 4830. Dorsum of body golden or somewhat yellowish, with one faint row of black chromatophores on predorsal region. Whitish or silvery midlateral stripe extending from posterior region of opercle to caudal peduncle. Ventral region of midlateral stripe with whitish or greenish iridescence. Humeral blotch absent. Dark blotch on caudal peduncle, reaching midlength of middle caudal-fin rays. Anal and dorsal fins with reddish or yellowish iridescence. Caudal fin yellowish on lobes and grayish on tips. Pectoral and pelvic fins hyaline. Head golden dorsally, with concentrated dark chromatophores on frontoparietal region. Premaxilla, anterior portion of maxilla, dentary, and lips (especially on lower jaw) with dark pigmentation and somewhat golden iridescence. 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 14–18 (Fig. 11 C). Pelvic-fin rays (rarely first ray without hooks) with short, slender, anteroventrally oriented hooks, more numerous on branched portion of rays; hooks usually paired or one per segment (few and unpaired on bases of rays). Anal fin with slender, anterodorsally or anterolaterally placed hooks with broad bases; from 3 to 24 pairs per ray located from posteriormost unbranched ray and up to ten anterior branched rays, larger hooks on middle rays of this range (one male with pair of minute hooks on posteriormost ray). In adult males, usually middle anal-fin rays slightly longer than remaining rays, resulting in convex-shaped anal-fin margin. In females, anal-fin rays gradually decreasing in length from anteriormost branched ray to posteriormost branched ray; anal-fin margin somewhat concave or straight. Anal-fin base of adult males slightly concave or curved along its midlength, this base straight in females. Adult females without externally developed urogenital papillae.
Males with anal and dorsal fins reddish in life; these fins yellowish and grayish in females. 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 or strong concavity on its ventral margin (Fig. 11 c). Second ventral procurrent ray somewhat longer than third ray, reaching distally two thirds of first ventral procurrent ray, and flattened in sagittal plane (especially on its distal portion). Posterior portion of third ventral procurrent ray weakly developed laterally. Pouch scale with 22–39 radii, usually located between caudal-fin ray 16 and third ventral procurrent ray. Posteroventral pouch-scale lobe well developed, extending along third ventral procurrent ray (Figs. 11 C–D). Dorsal margin of pouch scale attached via soft tissue (apparently connective) to caudal-fin rays 11 or 12 to 14. Posterior margin of pouch scale located between caudal-fin ray 14 or 15 and third ventral procurrent ray. Four scales in vertical series situated ventral to terminal lateral-line scale, overlaying posterior portion of pouch scale. Dorsal margin of pouch scale usually with small notch. Females with large scale with 19 (1), 21 (1), 21 (1), 23 (1), 24 (1), 26 (1), 29 (2), or 34 (1) radii on lower caudal-fin lobe.
Mature males with gill gland, formed by fusion of 2 (1), 7 (3), 8 (4), 9 (3), 10 (8), 11 (7), or 12 (4) anterior gill filaments of ventral limb of first gill arch. Total number of ventral limb gill filaments 21 (1), 22 (1), 23 (1), 24 (1), 25 (3), 26 (5), 27 (5), 28 (6), 29 (4), 30 (1), or 31 (2). Gill-gland length 2.5–4.0 % SL (mean = 3.2 % SL). Regression comparisons of morphometric data by sex with more pronounced differences in pectoral fin to pelvic fin length (higher values in females than in males), larger specimens separating on SL axis (Fig. 12).
Distribution. Gephyrocharax chocoensis is distributed in numerous drainages of the Atrato, León, and San Juan rivers basins in Colombia (Fig. 1).
Remarks. Eigenmann (1912) stated that the holotype of G. chocoensis was collected in Istmina (Chocó region), but he did not provide the precise river or creek where the fish was captured. According to the expedition itinerary provided by Eigenmann (1912: 7–8), he collected fishes in Istmina at night (within the limits of the San Juan River basin) and then he travelled northward arriving at Tambo (within the limits of the Atrato River basin). From these observations, it is possible to infer that the holotype could be collected in some drainage within the San Juan River basin or more probably in this river itself, since Istmina is located near the river. However, the precise drainage cannot be ascertained on the basis of this information.
Gephyrocharax chocoensis has a geographic variation in the presence/absence of humeral blotch, which is unique in the genus. The populations of the Atrato and León rivers basins possess a humeral blotch (although not intensely pigmented), whereas the populations of the San Juan River basin (e. g. holotype) lack this blotch. This difference between the populations is herein considered intrapopulational variation due to the fact that the presence/absence of the humeral blotch does not seem to be a sufficient reason for distinguishing two populations as distinct species. In the SPCA of the morphometric data, the populations were not differentiated along its components (Fig. 13). Additionally, the meristic, osteological, and myological data of both populations greatly overlap, which again reveal little evidence for the recognition of more than one species.
Material examined. All specimens from Colombia: AMNH 5330, 4, 39.6–45.1 mm SL, Chocó, San Juan River, Istmina, approximately 5°9'17.26"N 76°41'0.21"W 52 m a. s. l. STRI 1309, 1, 35.1 mm SL, Chocó, Atrato River basin, unknown creek, 5°37'8"N 76°44'11"W 43 m a. s. l. CAR 320, 6, 35.5–40.6 mm SL (2 c&s 38.5–40.6 mm SL), Chocó, Cabi River, tributary of Atrato River, approximately 5°40'0.15"N 76°37'58.39"W 46 m a. s. l. CAS 44278, 9 paratypes (previously IU 12671a–j in part), 42.6–52.1 mm SL, Chocó, San Juan River basin, upper San Juan River, Istmina, approximately 5°9'24.24"N 76°40'51.00"W 50 m a. s. l. CI-FML 6103, 5, 27.9–34.1 mm SL (2 c&s 29.9–34.1 mm SL), Antioquia, Carepa, Corpoica Farm, León River system, small creek, approximately 7°45'45.15"N 76°39'15.60"W 35 m a. s. l. CI-FML 6104, 3, 31.2–39.5 mm SL, Antioquia, Carepa, Corpoica Farm, León River system, small creek of slow waters, approximately 7°45'30.61"N 76°38'35.83"W 35 m a. s. l. FMNH 56016* (previously CM 4806), holotype of Gephyrocharax chocoensis, 48.2 mm SL (rad), male, [Chocó, San Juan River basin], Istmina, approximately 5°9'12.79"N 76°41'13.61"W 50 m a. s. l. IAvH-P 2228, 4, 28.5–39.7 mm SL, Chocó, Unguía, Atrato River basin, Ipeti creek, 8°4'29.1"N 77°5'51"W, 31 m a. s. l. IAvH-P 7233, 29, 22.8–43.2 mm SL, Chocó, Sucio River, Atrato River basin, Tendal creek, Vereda Sautata, Los Katios Nationals Natural Park, 7°51'0.1"N 77°8'44.5"W 36 m a. s. l. ICNMHN 1615, 47, 12.5–42.2 mm SL, Chocó, Quibdó, Atrato River basin, mouth of Quito River, approximately 5°41'4.77"N 76°40'1.46"W 36 m a. s. l. ICNMHN 2218, 3, 29.2–36.90 mm SL, Chocó, Atrato River basin, creeks at Quibdó-Istmina route, approximately 5°31'50.49"N 76°40'1.46"W 66 m a. s. l. ICNMHN 2265, 1, 41.5 mm SL, Chocó, San Juan River basin, Profundó, unknown drainage, approximately 5°11'36.02"N 76°36'51.08"W 85 m a. s. l. ICNMHN 2953, 4, 37.7–39.6 mm SL, Chocó, Lloró, Atrato River 2 km upstream mouth of Capa, approximately 5°32'28.67"N 76°29'34.44"W 68 m a. s. l. ICNMHN 3098, 1, 32.0 mm SL, Antioquia, León River system, Porroso River on Medellín-Urabá route, approximately 7°25'47.14"N 76°33'29.92"W 49 m a. s. l. ICNMHN 3378, 10, 38.0– 42.4 mm SL, Chocó, Lloró, La Vuelta, Atrato River basin, creek tributary to right side, third turn, approximately 5°28'4.37"N 76°32'1.14"W 86 m a. s. l. ICNMHN 3395, 11, 33.8–40.0 mm SL, Chocó, Quibdó, Atrato River basin, Samurindo River system, Carmelita creek, road Yutó- Quibdo km 15, approximately 5°34'49.50"N 76°37'35.28"W 82 m a. s. l. IMCN 4830, 12, 29.9–42.6 mm SL (2 c&s 38.9–39.4 mm SL, 2 ds 32.4–40.1 mm SL), Valle del Cauca, Calima, lower San Juan River basin, La Brea creek on lower portion of Calima River, approximately 3°59'59.89"N 76°59'0.13"W 28 m a. s. l. MCZ 30956*, 1, 49.4 mm SL (rad), Chocó, San Juan River, Istmina, approximately 5°10'60.00"N 76°39'0.00"W 71 m a. s. l. NRM 23834, 4, 22.8–30.3 mm SL, Chocó, Atrato River basin, creek crossed by Tutunendo-San Francisco de Ichó route, 1 km from San Francisco de Ichó, 5°45'N 76°32'W approximately 90 m a. s. l. NRM 23835, 30, 20.4–33.5 mm SL, Chocó, Atrato River basin, creek at Tutunendo-San Francisco de Ichó route, 1.5 km from San Francisco de Ichó, 5°47'N 76°32'W approximately 59 m a. s. l. NRM 23836, 25, 33.4–43.5 mm SL, Chocó, Atrato River basin, Taridó creek at Pan-American highway, 5°28'N 76°44'W approximately 43 m a. s. l. NRM 23837, 7, 27.8–37.4 mm SL, Chocó, San Juan River basin, Condoto River, bank on right beach below bridge at Condoto, 5°6'N 76°40'W approximately 58 m a. s. l. USNM 76973 (possibly IU 12671a–j in part), 12 paratypes, 29.3–47.6 mm SL, [Chocó, San Juan River basin], Istmina, approximately 5°9'12.79"N 76°41'13.61"W 50 m a. s. l. USNM 79208 (possibly CM 4807a–j in part) 2 paratypes, 46.2–48.1 mm SL (2 rad), [Chocó, San Juan River basin] Istmina, approximately 5°9'12.79"N 76°41'13.61"W 50 m a. s. l.
description: Published as part of Vanegas-Ríos, James A., 2016, Taxonomic review of the Neotropical genus Gephyrocharax Eigenmann, 1912 (Characiformes, Characidae, Stevardiinae) in Zootaxa 4100 (1) on pages 22-30, DOI: 10.11646/zootaxa.4100.1.1, http://zenodo.org/record/261565