Gephyrocharax atracaudatus ( Meek & Hildebrand, 1912 )

Vanegas-Ríos, James A., 2016, Taxonomic review of the Neotropical genus Gephyrocharax Eigenmann, 1912 (Characiformes, Characidae, Stevardiinae), Zootaxa 4100 (1) : 9-15

Gephyrocharax atracaudatus ( Meek & Hildebrand, 1912)

( Figs. 4–5 )

Deuterodon atracaudata Meek & Hildebrand, 1912: 68 [original description based on single specimen, incorrect original spelling, holotype FMNH 7573, type locality: “Rio Frijoles, C. Z., Panama ” (= Panama: Canal Zone, Frijoles River)].

Gephyrocharax atricaudata . Eigenmann, 1914: 41 [new combination, key, name misspelled]. Meek & Hildebrand, 1916: 226, 229, 231–232, 277–278 [key, morphological data, name misspelled]. Eigenmann, 1920b: 15 [listed from east of Panama]. Eigenmann, 1922: 156 [catalogue, name misspelled]. Breder, 1927: 125, 148, 150, 158, 163, 168 [color variation in juveniles, distributional records for eastern Panama, key, name misspelled]. Hildebrand, 1938: 252 –253 [diagnostic characters, expanded distributional range, name misspelled]. Weitzman & Fink, 1985: 24, 29, 116 [comments on morphology and behavior in aquarium, name misspelled].

Gephyrocharax atracaudatus . Breder, 1925: 144 [ Panama: Tapia River]. Myers in Eigenmann & Myers, 1929: 477, 482–483, pl. 63, fig. 4 [key, redescription]. Schultz, 1944: 322 [key]. Bushmann, Burns & Weitzman, 2002: 189 [gill gland morphology]. Burns & Weitzman, 2005: 121, fig. 14 [sexual dimorphism comments]. Oliveira, Abelino, Abe, Mariguela, Benine, Ortí, Vari & Castro et al., 2011: 16, fig. 12 [phylogenetic relationships, placed in Stevardiinae ]. Tagliacollo, Souza-Lima, Benine & Oliveira, 2012: 302, fig. 2 [combined phylogeny, placed in Stevardiinae ]. Bonilla-Rivero & López- Rojas, 2013: 489, fig. 1 [distribution map]. Thomaz, Arcila, Ortí & Malabarba, 2015: 5, table 2, Add. File 5 [comments on insemination strategy, tentative classification]. [correct spelling]

Gephyrocharax atricuadata . Breder, 1927: 144 –145, 149 [listed from Chucunaque and Tuquesa rivers, name misspelled].

Gephyrocharax atricaudatus . Miller, 1966: 137 [recorded for several drainages in Pacific and Caribbean versants from Panama, data compilation, name misspelled]. Weitzman & Fink, 1985: 18, 29, 96, 103, 116, fig. 17 [illustration of caudal skeletal, comments on morphology of males and behavior in aquarium, name misspelled]. Burns, Weitzman, Grier & Menezes, 1995: 133–138, figs. 1–3 [evidence of insemination, spermatozoid morphology, name misspelled]. Burns, Quagio-Grassioto & Jamieson, 2009: 329–330, fig. 11.29 [details on spermatozoids, name misspelled].

Gephyrocharax atracaudata . Bussing, 1974: 139 [compared with Pterobrycon myrnae Bussing , examined material, name misspelled]. Weitzman, 2003: 224 [catalogue, name misspelled]. Ferreira, Menezes & Quagio-Grassiotto, 2011: 283, 290 [phylogenetic relationships, examined material, name misspelled]. Thomaz, Arcila, Ortí & Malabarba, 2015: 5, 10, table 2, fig. 5, Add. Files 2, 5 [comments on sperm morphology, name misspelled].

Diagnosis. Gephyrocharax atracaudatus differs from its congeners by the presence of an intense dark pigmentation extending onto the dorsal and ventral procurrent rays and onto the principal caudal-fin rays 1 to 6 and 14 to 19 (vs. absence of this pigmentation, with hyaline, light gray or slightly yellowish rays) and by having the first ventral procurrent ray of caudal fin strongly concave and associated to a strong sagittal expansion on the distal portion of the second ventral procurrent ray in adult males (vs. first ventral procurrent ray straight or slightly concave, and weakly associated to the distal portion of the second ray, except in G. intermedius ). The lack of a lobe on the posteroventral margin of the pouch scale in adult males (vs. presence of this lobe) differentiates G. atracaudatus from almost all its congeners (except G. intermedius and G. major ). Gephyrocharax atracaudatus differs from G. m e l a n o c h ei r, G. t o r re s i, and G. valencia by having a terminal-lateral line tube between caudal-fin rays 10 and 11 (vs. absence of this tube). From G. caucanus , G. melanocheir , G. sinuensis , G. v a l e n c i a, and G. venezuelae it is also distinguished by having the anterior fontanel completely occluded by the contact between frontals in adult specimens (vs. fontanel well developed or reduced to a small opening). Gephyrocharax atracaudatus differs from G. chocoensis , G. m a r t a e, G. s i n u e n s i s, and G. torresi by the number of pouch-scale radii in adult males (11–20 vs. 21–43). The species is distinguished from G. m a r t a e, G. melanocheir and G. torresi by the gill-gland length (0.5–3.4 % SL vs. 6.0-11.4 % SL). Additionally, Gephyrocharax atracaudatus is distinguished from G. m a r t a e by the snout to pectoral-fin origin length (23.0–30.1 % SL vs. 20.7 % SL) and from G. caucanus by the fewer number of lateral-line scales (36–41 vs. 42–47), branched anal-fin rays (24–29 vs. 29–36), and vertebrae (37–39 vs. 41–42).

Description. Morphometric data in Table 1 . Largest male 48.8 mm SL, largest female 46.2 mm SL. Body laterally compressed, maximum depth at vertical through pelvic-fin origin or slightly anterior to this point. Dorsal profile of head slightly convex from margin of upper lip to tip of supraoccipital spine. Dorsal profile of body straight or somewhat convex from that point to dorsal-fin origin, slanting posteroventrally along dorsal-fin base, straight from posteriormost dorsal-fin ray to caudal peduncle ( Fig. 4 ). Ventral profile of body convex from tip of dentary to vertical crossing posterior half of pectoral fin, slightly convex from this point to anal-fin origin, slanting posterodorsally and straight (or sometimes slightly concave) from this point to caudal peduncle origin. 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 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

Mouth superior, lower jaw projecting slightly anterior to tip of upper jaw. Premaxilla with two rows of teeth. Outer row with 2 (1), 3 (13), 4* (50), 5 (6), or 6 (1) teeth; usually tricuspid, rarely bicuspid. Inner row with 4 (58) or 5* (13) teeth; symphyseal tooth tetracuspid, remaining teeth pentacuspid. Maxilla with 1* (38), 2 (28), 3 (4), or 4 (1) teeth; usually tri- to pentacuspid, rarely bicuspid ( Fig. 5 A). Maxilla posteriorly reaching vertical through anterior one-third of eye. Dentary with 10 (8), 11 (9), 12 (13), 13* (10), 14 (7), 15 (4), 16 (3), or 18 (1) teeth; three anteriormost teeth larger, pentacuspid, followed by one median-sized tooth usually pentacuspid, and 6 (10), 7 (9), 8 (13), 9* (10), 10 (7), 11 (4), 12 (3), or 14 (1) smaller conical, tri- or tetracuspid teeth ( Fig. 5 B).

Dorsal-fin rays ii,7 (10), 8* (65), or 9 (1). Nine* proximal pterygiophores on dorsal fin (8 rad, 2 c&s). Dorsalfin origin located at vertical between anal-fin rays 5–10. Adipose-fin origin located at vertical through base of two or four posteriormost anal-fin rays or caudal peduncle origin. Anal-fin rays iv (15), v* (60), vi (1), or vii (1), 24 (2), 25* (18), 26 (25), 27 (21), 28 (10), or 29 (1) (one deformed specimen with v, 23 rays not included in counts). Twenty-six* to 28 proximal pterygiophores on anal fin (8 rad, 2 c&s). Anal-fin origin closer to origin of hypural joint than to snout tip. Pectoral-fin rays i,8 (2), 9 (45), 10 (20), or 11* (4). Pectoral-fin distal tip posteriorly reaching one-third to one-half of pelvic-fin length. Pelvic-fin rays i,6* (12) or 7 (59). Pelvic-fin origin located at vertical between pored lateral-line scales 8–10 and slightly anterior to body midlength. Caudal fin forked with 10/9 principal rays in all specimens.

Scales cycloid, with variable number of radii along posterior region. Lateral line complete, pored scales 36 (1), 37* (6), 38 (10), 39 (25), 40 (11), or 41 (3) ( Fig. 6 ). Terminal lateral-line tube present. Predorsal scales 17 (5), 18 (17), 19* (25), 20 (8), or 21 (2). Scale rows between dorsal fin and lateral line 6* (46) or 7 (11). Scale rows between lateral line and anal fin 5* (46) or 6 (11). Scale rows between lateral line and pelvic fin 4 (5) or 5* (52). Circumpeduncular scales 14 (3), 15 (17), 16 (34), or 17 (1) (scales lost in holotype). One row of 12 (1), 13 (4), 14 (5), 15 (5), 16 (2), 17 (5), 18 (3), 19 (1), 20 (22), or 21 (1) scales forming sheath along anal-fin base. Total number of vertebrae 37 (3), 38* (4), or 39 (3); 15* (5) or 16 (5) precaudal and 21 (1), 22 (3), or 23* (6) caudal (8 rad, 2 c&s). Gill-rakers on dorsal limb of first branchial arch 5 (1), 6 (47), or 7* (17); ventral limb with 11 (13) or 12* (51).

Color in alcohol. Ground color pale yellowish or dark brown, darker along mid-dorsal line, slightly lighter ventrally. Minute dark chromatophores covering body, less numerous on lateral and ventral regions of abdomen and ventral region of caudal peduncle. Dark midlateral stripe diffuse, extending from posterior region of humeral blotch to middle or posterior portion of caudal peduncle. Dark chromatophores present along myosepta between lateral line and upper portion of anal fin. Dark humeral blotch vertically elongate. Large dark blotch on caudal peduncle, conspicuous especially on its posterior portion, and slightly reaching base of middle caudal-fin rays and interradialis muscles. Anal and dorsal fins light gray, faintly darkened by concentration of chromatophores on rays and/or membranes. Bicolored caudal fin; middle rays light gray or light yellow, with few dark chromatophores on its membranes; dorsal and ventral procurrent rays plus principal rays 1–6 and 14–19 intensely pigmented by dark chromatophores. Pectoral and pelvic fins light gray, with scattered dark chromatophores on rays. Head darker dorsally than ventrally. Few dark chromatophores on opercle and infraorbitals. 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 13–17 ( Fig. 5 C). Pelvic-fin rays with short, slender, anterolaterally or anteroventrally oriented hooks, more numerous on branched portion of each ray (sometimes reduced in number on unbranched and innermost rays); hooks usually paired or one per segment (frequently unpaired and fewer on bases of rays). Anal fin with slender, anterodorsally or anterolaterally placed hooks with broad bases; from two to 32 pairs per ray located from posteriormost unbranched ray and up to ten anterior branched rays (larger hooks on middle rays of this range). In adult males, posteriormost unbranched analfin ray and 18 anterior branched rays 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 straight or slightly concave. Anal-fin base of adult males concave or curved on its midlength, this base straight in females. Adult females without externally developed urogenital papillae.

Second and third ventral procurrent rays of caudal fin more intensely pigmented with dark chromatophores in females than in males. Anal-fin chromatophores of males slightly more concentrated on rays bearing bony hooks than on remaining rays. Mature males with hypertrophied scale forming pouch on lower caudal-fin lobe, with ventral procurrent rays 2 and 3 forming spur-shaped structure. Scarce small aggregations of apparent glandular tissue located on caudal-fin rays, medially to pouch scale. First ventral procurrent ray with strong concavity on its ventral margin ( Fig. 5 C). Second ventral procurrent ray somewhat longer than third ray, reaching midlength of first ventral procurrent ray distally, and strongly flattened in sagittal plane. Distal portion of third ventral procurrent ray more developed laterally than sagittally. Pouch scale with 11–20 radii, usually located between caudal-fin rays 16 or 17 and second ventral procurrent ray. Posteroventral pouch-scale lobe absent ( Figs. 5 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 second ventral procurrent ray. Three or four scales in vertical series situated ventral to terminal lateral-line scale, overlapping posterior portion of pouch scale. Dorsalmost scale of this vertical series with somewhat undulated margin and with minute, medial spiny patch oriented toward dorsal margin of pouch scale. Anterodorsal margin of pouch scale usually with small notch. Females with large scale with 14 (1), 18 (1), or 21 (1) radii on lower caudal-fin lobe.

Mature males with gill gland, usually well developed in specimens with bony hooks on caudal fin (weakly developed in two adult specimens of 36.5 mm SL and 44.1 mm SL). Gill gland formed by fusion of 2 (1), 4 (3), 5 (1), 6 (3), 9 (1), or 11 (1) anterior gill filaments of ventral limb of first gill arch. Total number of ventral limb gill filaments 23 (1), 24 (1), 25 (5), 26 (1), 27 (1), or 28 (1). Gill-gland length 0.5–3.4 % SL (mean = 1.7 % SL). Regression comparisons of morphometric data by sex with major differences in pectoral fin to pelvic fin length (higher values in females than in males) and caudal-fin depth (higher values in males than in females), but larger specimens not completely separating on SL axis.

Distribution. Gephyrocharax atracaudatus is distributed in numerous drainages from the Canal Zone of Panama across the Pacific and Caribbean versant to the Pear islands in the Gulf of Panama ( Fig. 1 ).

Ecological notes. Kramer (1978) published some reproductive data of populations from the Canal Zone system in Panama, Kramer & Bryant (1995a, b) described the diet of populations from the Chagres River basin, and Zaret & Rand (1971) reported some data on ecological competition.

Remarks. The specific epithet “ atracaudata ” is an adjective in apposition originated from combining the words atra (Latin = dark ) and cauda (Latin = tail of an animal), which denote the characteristic dark pigmentation of caudal fin in the species. Both Deuterodon and Gephyrocharax are masculine genders, but the ending “ caudata ” is a feminine declination. According to the ICZN (1999: articles 31.2, 34.2), the epithet must agree in gender with the generic name when it is used as adjective, for this reason, the correct spelling should be “ atracaudatus ”, which represent a masculine declination.

The holotype of G. atracaudatus is a female with body partially scaleless and poorly colored (except caudal-fin pigmentation), but fins and teeth are in good conditions. This single specimen was used for the species description ( Meek & Hildebrand 1912), which neither included diagnosis nor illustration. Meek & Hildebrand (1916) redescribed this species based on a larger number of specimens, and then Myers (in Eigenmann & Myers 1929) and Hildebrand (1938) concluded that the bicolored caudal fin was useful to differentiate G. atracaudatus from G. intermedius and G. whaleri .

Gephyrocharax atracaudatus is recorded for the first time from the Palenque River in the Pearls islands, Pacific coast of Panama (STRI 1161). This is the second record of the genus confirmed for a freshwater insular drainage (see also G. valencia ).

Material examined. Panama: AMNH 11233, 4, 24.5–28.3 mm SL, Tapia, Tapia River, approximately 9°5'50.50"N 79°24'52.82"W 60 m a. s. l. AMNH 11488, 2, 24.8–25.1 mm SL, Darién, mouth of Metiti River on Chucunaque River, approximately 8°31'28.41"N 77°53'57.15"W 34 m a. s. l. AMNH 11518, 5, 23.2–28.5 mm SL, Darién, mouth of Membrillo River on Chucunaque River, approximately 8°35'25.19"N 77°54'57.73"W 39 m a. s. l. AMNH 37808, 20, 29.1–38.2 mm SL, Panama, Canal Zone, Juan Grande creek near Gamboa, approximately 9°7'0.00"N 79°42'0.00"W 39 m a. s. l. AUM 32108, 10, 30.4–45.6 mm SL, Colón, Caribbean versant, Chagres River system, Frijoles River, Pipeline highway at 4.6 km, 9°9'8.35"N 79°44'5.28”W 68 m a. s. l. AUM 31666, 8, 22.6–39.4 mm SL, Pacific versant, Chepo River system (Bayano), Cañita River, 27 km ENE Chepo on Pan- American highway, 9°13'7.72"N 78°50'41.09"W 38 m a. s. l. FMNH 7573, holotype of Deuterodon atracaudatus , 39.7 mm SL (rad), female, Frijoles, Canal Zone, Frijoles River, approximately 9°9'8.35"N 79°44'5.28"W 68 m a. s. l. INHS 68120, 19, 24.0– 42.8 mm SL, Colón, Chagres River system, Frijoles River, Soberania National Park, approximately 9°4'27.47"N 79°39'35.31"W 90 m. a. s. l. LACM 56197.005, 4, 19.6–32.1 mm SL, Panama, Cardenas River, at the bridge and up Fort Clayton, 9°0'18.72"N 79°34'12.00"W 26 m a. s. l. MCZ 32827*, 2, 21.2– 24.1 mm SL (2 rad), Darién, Jesusito River, approximately 7°59'28.82"N 78°17'26.17"W, 49 m a. s. l. MCZ 32828*, 1, 42.2 mm SL (rad), Darién, Esnape River, possible tributary of Taimati River, approximately 8°9'0.00"N 78°13'59.79"W, 14 m a. s. l. MCZ 57071*, 1, 34.4 mm SL (rad), Panama, in Culvert 11 km from the Bayano bridge at Pan-American highway, small dried creek, approximately 9°9'21.88"N 78°41'47.50"W, 86 m a. s. l. MCZ 57072*, 1, 38.0 mm SL (rad), Panama, Bayano drainage, tributary of Cañita River, small tributary from mainstream on left about 0.75 km upriver of the bridge on Pan-American highway, near to camps and constructions places, approximately 9°12'36.80"N 78°50'55.96"W 35 m a. s. l. MCZ 57070*, 1, 29.6 mm SL (rad), Panama, Bayano drainage, a small stream about 3km W of El Llano on the Chepo-El Llano road, approximately 9°13'9.54"N 78°59'56.05"W 29 m a. s. l. MCZ 57073*, 1, 30.4 mm SL (rad), Panama, possibly Parti River (Bayano system), off Pan-American highway about 30km E of the Bayano bridge, approximately 9°3'16.16"N 78°39'19.81"W 107 m a. s. l. STRI 1161, 1, 35.7 mm SL, The Pearl islands, Palenque River, 8°20'27"N 78°55'36"W 23 m a. s. l. STRI 1168, 2, 37.7–37.8 mm SL, Darién, Tuira River basin, Yape River, 8°06'8.41"N 77°31'9.82"W 126 m a. s. l. STRI 1174, 2, 28.9–29.0 mm SL, Darién, Tuira River basin, Membrillo River about 1.5 hrs. toward north of Sinai, 8°37'33"N 77°49'01"W 41 m a. s. l. STRI 1178, 2, 37.7–39.6 mm SL, Panama, Chagres River basin, Cerro Azul, Indio River, 9°11'5.61"N 79°26'6.08”W 482 m a. s. l. STRI 1185, 2, 38.8–41.2 mm SL, Bayano River basin, Mamoni River, 9°12'59"N 79°04'59"W 43 m a. s. l. STRI 1190, 2, 40.3–41.2 mm SL, Panama, Bayano River basin, creek on Aguas Claras River, 9°16'25.7"N 78°40'52.8"W 104 m a. s. l. STRI 7228, 2 c&s, 43.5–44.1 mm SL, Panama, Chagres River, 9°21'36.3"N 79°19'20.1"W 328 m a. s. l. USNM 226469, 2, 40.0–43.0 mm SL, Panama, Canal Zone, Chagres River basin, Juan Grande creek on Pipeline road approximately 9°7'42.62"N 79°42'55.06"W 66 m a. s. l. USNM 226470, 7 c&s, 28.4–48.8 mm SL, Panama, Canal Zone, Chagres River basin, Juan Grande creek on Pipeline Road approximately 9°7'42.62"N 79°42'55.06"W 66 m a. s. l. USNM 236086*, 1 c&s, 47.4 mm SL, creek by road, 8 miles to north of Cerro Azul, 9°11'60.00"N 79°26'60.00"W, 397 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 4. Gephyrocharax atracaudatus, (A) female, holotype, 39.7 mm SL, FMNH 7573; (B) male, 37.7 mm SL, STRI 1178; (C) female, 38.2 mm SL, AMNH 37808. Additional illustration in Burns & Weitzman (2005: fig. 14).

FIGURE 5. Gephyrocharax atracaudatus, (A – B) upper and lower jaws, female, 43.5 mm SL, STRI 7228; (C – D) detail of lower caudal skeleton and associated pouch scale, male, 44.1 mm SL, STRI 7228. Anguloarticular: aa, dentary: dt, maxilla: mx, premaxilla: pm, pouch scale: ps, principal caudal-fin ray: pcr, retroarticular: ra, spur-shaped structure: sss, ventral procurrent ray: vpr. Lateral view, left side. Scale = 1 mm.

FIGURE 6. Tukey box plots of (A) number of maxillary teeth, (B) number of branched anal-fin rays, (C) number of branched pelvic-rays, and (D) number of lateral-line scales comparing among Gephyrocharax species. Number of specimens between brackets.

Tables

TABLE 1. Morphometric data of holotype and examined species of Gephyrocharax atracaudatus. Range of females and juveniles including holotype values. M = mean; SD = standard deviation.

	Holotype	n	Range	M	SD	n	Range	M	SD
Standard length (mm)	39.7	43	24.9–48.8	35.9	5.7	50	21.2–46.2	33.4	6.7
Percentages of standard length:
Depth at dorsal-fin origin	36.3	36	27.9–38.3	32.6	2.4	47	27.5–38.5	30.9	6.9
Snout to dorsal-fin origin	68.3	36	59.9–66.5	64.4	1.7	47	62.1–68.7	62.5	13.1
Snout to pectoral-fin origin	23.0	36	25.7–29.5	27.7	1.0	47	23.0–30.1	26.6	5.7
Snout to pelvic-fin origin	43.5	36	42.7–48.6	45.3	1.5	47	43.5–50.1	45.0	9.5
Snout to anal-fin origin	65.6	36	55.9–62.5	59.4	1.5	47	58.2–65.6	58.9	12.5
Dorsal fin to pectoral fin length	50.9	36	44.6–52.1	48.6	2.0	47	42.5–53.4	46.7	10.0