Gephyrocharax torresi, Vanegas-Ríos & Azpelicueta & Mirande & Gonzales, 2013

Vanegas-Ríos, James Anyelo, Azpelicueta, María de las Mercedes, Mirande, Juan Marcos & Gonzales, María Dolly García, 2013, Gephyrocharax torresi (Characiformes: Characidae: Stevardiinae), a new species from the río Cascajales basin, río Magdalena system, Colombia, Neotropical Ichthyology 11 (2), pp. 275-284 : 276-280

Gephyrocharax torresi , new species

Figs. 1-6

Holotype. UIST 1767 , 36.7 mm SL, male, Colombia, Santander, El Carmen, río Magdalena basin, río La Colorada basin, río Cascajales system, río Sucio basin, Caño Volador , 6°39’56.44”N 73°34’47.36”W, approximately 338 m a.s.l., 17 Dec 2009, M. Torres.

Paratypes. All from Colombia, Santander: AI 293 , 1 male c&s, 34.7 mm SL, AI 294 , 2 , 34.0-36.0 mm SL, and UIST 1751 , 19 , 26.3-37.3 mm SL (1 c&s, 36.0 mm SL), El Carmen, río Magdalena basin, río La Colorada basin, río Cascajales system, río Sucio under bridge to Vereda Islandia, 6°41’14.6”N 73°35’15.10”W, approximately 280 m a.s.l., 16 Dec 2009, M. Torres. AI 295 , 2 , 35.1 -39.0 mm SL, and UIST 1766 , 12 , 32.0-42.0 mm SL, collected with holotype .

Diagnosis. Gephyrocharax torresi is readily distinguished from its congeners (except G. melanocheir ) by the absent or vestigial adipose fin (vs. the presence of a well developed adipose fin), the form of lateral branched pectoral-fin ray of males which has a highly developed branching pattern that distally forms a fan-shaped structure with minute branches (vs. less extensive branching pattern not distally forming a fan-shaped structure with such minute branches), and the distal portion of this pectoral-fin ray in males with minute bony hooks (vs. hooks absent) and a dark blotch or a few scattered dark brown chromatophores along its branches (vs. blotch or chromatophores absent). Gephyrocharax torresi differs from G. melanocheir by lacking intense black pigmentation at the base of the anterior five dorsal-fin rays (vs. the presence of such pigmentation), the number of vertebrae (40-41 vs. 38-39), the frontals contacting each other anterior to epiphyseal bar in adults (vs. the absence of contact), the posterior margin of the mesethmoid straight in its central portion (vs. strongly concave at this point), the pouch scale of mature males reaching caudal-fin ray 11 or the area between caudal-fin rays 11 and 12 (vs. reaching only to caudal fin ray 10 or the area between caudal-fin rays 9 and 10), the number of minute terminal branches of the lateral branched pectoral-fin ray of mature males (60-88 vs. 28-54), the longer midlateral black body stripe in males (reaching to the base of the caudal-fin rays vs. reaching to the middle of the caudal peduncle), and the snout length (28.3-31.8% HL vs. 22.1-28.0% HL).

Description. Morphometric data in Table 1. Largest male 37.3 mm SL and largest female 42.0 mm SL. Body laterally compressed, with maximum depth at vertical through pelvic-fin origin. Dorsal profile of head slightly convex from margin of upper lip to tip of supraoccipital spine. Dorsal profile of body straight from posterior portion of supraoccipital spine to dorsal-fin origin, slanting posteroventrally along dorsal-fin base, straight from posterior most dorsal-fin ray to caudal peduncle ( Fig. 1). Ventral profile of body convex from tip of snout to pectoral-fin origin, slightly convex between vertical through pectoral-fin and pelvic-fin origins, slanting posterodorsally and straight from this point to caudal peduncle. Anterior fontanel absent or reduced to narrow 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 point half way between posterior pore of nasal bone and nostrils to posterior portion of frontals. Smaller groove with few neuromasts between nostrils and nasal bones.

Dorsal-fin rays ii,7* (14) or 8 (23); proximal pterygiophores 9. Dorsal-fin origin located at vertical through base of anal-fin rays 5 to 8. Adipose fin reduced in size (6) or absent* (31). When present, adipose fin located at vertical through base of four or five posterior most anal-fin rays. Anal fin with 4* (30) or 5 (7) unbranched rays followed by 26 (1), 27 (4), 28 (9), 29* (14), or 30 (9) branched rays.Anal-fin proximal pterygiophores 29-30. Anal-fin origin closer to origin of hypural joint than to snout tip. Pectoral-fin rays i,8 (5), 9 (25), 10* (6), or 11 (1). Pectoral fin long, extending posteriorly to one-third or more of vertical through pelvic-fin origin. Pelvic-fin rays i,6* (37). Pelvic-fin origin located at vertical through lateral-line scales 9 to 11 and slightly anterior to midpoint of body. Caudal fin forked with 10/9 principal rays in all specimens.

Mouth superior, lower jaw projecting slightly anterior to tip of upper jaw. Premaxilla with two rows of teeth. Outer row with 3* (30) or 4 (7) usually tricuspidate, rarely bicuspidate teeth. Inner row with 4* (33) or 5 (4) teeth; symphyseal tooth tetracuspidate and remaining teeth pentacuspidate. Maxilla with 1 (23), 2 (13), or 3* (1) teeth; all teeth tricuspidate or tetracuspidate ( Fig. 2a ). Maxilla long, reaching posteriorly to vertical through anterior one-third of eye. Dentary with 9 (1), 10 (1), 11 (7), 12 (8), 13* (7), or 14 (2) teeth: three anterior most teeth large and pentacuspidate and followed by one median sized, usually tricuspidate tooth and 5 (1), 6 (1), 7 (7), 8 (8), 9* (7), or 10 (2), tricuspidate or conical smaller teeth ( Fig. 2b ).

Scales cycloid, with several radii along posterior field. Lateral line complete. Pored scales 40 (1), 41 (10), 42 (15), 43* (10), or 44 (1); one specimen with lateral line interrupted, with several scales lacking pores. Terminal lateral-line tube absent. Predorsal scales 18* (9), 19 (20), 20 (5), or 21 (3). Scale rows between dorsal fin and lateral line 5 (3) or 6* (34). Scale rows between lateral line and anal fin 4 (13) or 5* (24). Scale rows between lateral line and pelvic fin 4* (1) or 5 (26). Circumpeduncular scales 14 (16), 15* (18), or 16 (3). One row of 14 (3), 15 (3), 16 (8), 17* (5), 18 (3), 19 (3), 20 (8), 21 (1), or 22 (3) scales forming sheath along anal-fin base. Total number of vertebrae 40-41 (in two c&s specimens). Gill-rakers on dorsal limb of first branchial arch 5 (1) or 6* (21); ventral limb with 11 (1), 12 (18), or 13* (3).

hyaline with few scattered, dark brown or black chromatophores on rays and membranes. Pectoral and pelvic fins hyaline with scattered black chromatophores on rays. Head darker dorsally. Few dark brown chromatophores distributed on opercle and infraorbitals. Premaxilla, anterior portions of maxilla, dentary, and lips with dark brown chromatophores. Snout heavily pigmented by dark brown chromatophores. Variations in color pattern between males and females discussed under sexual dimorphism.

Sexual dimorphism. Male, but not female, specimens of Gephyrocharax torresi with bony hooks on rays of anal, caudal, pectoral and pelvic fins. Caudal fin with short, slender anterodorsally oriented hooks on unbranched Color in alcohol. Ground color pale yellowish, darker along mid-dorsal line and slightly lighter ventrally. Minute brown chromatophores completely covering body. Black lateral stripe extending from posterior region of opercle to central or posterior portion of caudal peduncle. Dark brown chromatophores present along myosepta between lateral line and upper portion of anal fin. Humeral spot vertically elongate. Large dark brown spot on caudal peduncle. Dorsal fin dusky with dark brown chromatophores concentrated on rays and membranes. Anal fin dusky with dark brown and black chromatophores located on membranes: chromatophores on anterior and distal portions of fin usually more densely concentrated in males. Caudal fin portions and dorsal branches of rays 14-18 ( Fig. 4). All rays of pelvic fin with slender, anterolaterally oriented hooks along nearly entire length of each ray; usually one pair per segment. Pectoral fin with few scattered, minute bony hooks on distal portion of lateral branched ray. Anal fin with slender, anterodorsally placed hooks with broad bases, one pair per segment. From three to 12 pairs of hooks located on posterior most unbranched and up to first seven branched rays. Posterior most unbranched and first 18 branched anal-fin rays gradually decreasing in length in males; females with posterior most unbranched and anterior 1-3 branched anal-rays longer than remaining rays. Mature females with large, usually posteroventrally oriented, conical urogenital papilla ( Fig. 1b).

Caudal spot of males only reaching base of caudal-fin rays but extending over middle caudal-fin rays in females. Males with caudal spot chromatophores bounding pouch scale dorsally but leaving clear area in lower portion of caudal peduncle, whereas females with that spot extending completely onto caudal peduncle. Lateral stripe of males bounding caudal spot dorsally versus ending on anterior or middle portions of caudal spot in females. Males differ from females in presence of dark blotch or few scattered dark brown chromatophores on distal portion of lateral branched pectoral-fin ray but rarely on contiguous proximal ray. Distal portion of lateral branched pectoral-fin ray modified in both sexes; branching more complex in males. In males, posterior half of external branched pectoral-fin ray thicker, splitting into two equal branches; each branch dividing into three smaller branches and each one of these six branches splitting further to form distal structure with 60 (1), 61 (1), 62 (2), 64 (1), 70 (3), 72* (1), 78 (1), or 88 (1) minute branches ( Fig. 3 ). In females, lateral branched pectoral-fin ray splits into two principal branches; outer branch divides into four short branches and inner into three short branches. Each of these seven slender branches usually splits one more time.

Males with modified scale forming pouch on lower lobe of caudal fin and with ventral procurrent rays 2 and 3 in form of a claw-shaped structure immediately ventral to ray 9 of lower lobe of caudal fin (lower caudal fulcra free and forming peculiar spur described by Eigenmann, 1912). Tissue of glandular appearance located on caudal-fin rays and medially to pouch scale. Second ventral procurrent ray somewhat longer than third ray. Claw-shaped structure incompletely ossified distally; claw reaching half length of first ventral procurrent ray ( Fig. 4). Hypertrophied pouch scale usually with 26 or 30 radii; first 22 radii often located between caudal-fin rays 17 or 18 and second ventral procurrent ray, remaining radii distributed from that point to lateral border of third ventral procurrent ray. Posteroventral portion of pouch scale fused to third ventral procurrent ray. Dorsal surface of pouch scale attached via soft tissue to caudal-fin rays 9 to 15. Posterior margin of pouch scale located between caudal-fin ray 15 and third ventral procurrent ray. Four or five scales in vertical series just below posterior most lateral-line scale and on posterior portion of pouch scale. Median scale with undulated margin located between these scales and pouch scale. Series of minute spinous processes forming patch on dorsal portion of pouch scale. Females with large scale with 20 (1), 21 (3), 22 (2), 24 (2), 26 (2), 27 (1), 28 (2), or 29 (3) radii on lower caudal-fin lobe.

Mature males with long gill gland (two juvenile males with poorly developed gill gland excluded from following counts). Gill gland formed by modified ventral 11 (1), 12 (1), 14 (1), 20 (2), 21 (3), 22* (3), 23 (3), or 24 (2) gill filaments of ventral limb of first functional branchial arch. Total gill filaments on ventral limb 23 (2), 24 (1), 25 (3), 26 (2), 27 (2), 28 (2), 29 (2), or 30* (2), n = 16. Gill-gland length 6.0-10.3% SL (mean = 8.6% SL), 8.7% SL*. Standard and gill-gland lengths positively correlated (normality test, respectively: W = 0.89, p = 0.055, n = 16, W = 0.88, p = 0.038; Spearman test: r = 0.83, p <0.001). Caudal-peduncle depth, pectoral-fin to pelvic-fin length, pelvic-fin length, and caudal-peduncle length sexually dimorphic as function of SL and with differences more pronounced in larger specimens ( Fig. 5 ). Males with higher values than females in all these measurements except pectoral-fin to pelvic-fin length.

Distribution. Gephyrocharax torresi is known from two localities of the río Sucio basin, río Cascajales system, río La Colorada basin, río Magdalena basin, Colombia ( Fig. 6 ).

Etymology. The species name torresi is treated as a patronym in gratitude and recognition of Mauricio Torres who collected the material on which the description is based.

Figures

Fig. 2. Lateral view of jaws and dentition of Gephyrocharax torresi, UIST 1751, paratype female, 36.7 mm SL, right side. (a) Premaxilla and maxilla. (b) dentary, anguloarticular, and retroarticular bones.

Fig. 3. Lateral view of lateral branched pectoral-fin ray of Gephyrocharax torresi, AI 293, paratype male, 34.7 mm SL, left side. Scale bar = 1 mm.

Fig. 5. Comparative regression plots of males (n = 18) and females (n = 19) of Gephyrocharax torresi.All variables as function of SL: (a) Caudal-peduncle depth (females: r2= 0.95; males: r2= 0.94), (b) caudal-pedunclelength (females: r2= 0.87; males: r2= 0.73), (c) pectoral fin to pelvic fin length (females:r2= 0.87; males: r2= 0.74), (d) pelvic-fin length (females: r2 = 0.89; males:r2= 0.94).

Fig. 6. Geographic distribution of Gephyrocharax torresi (black rhomboids).