Gephyrocharax martae Dahl, 1943

Vanegas-Ríos, James A., 2016, Taxonomic review of the Neotropical genus Gephyrocharax Eigenmann, 1912 (Characiformes, Characidae, Stevardiinae), Zootaxa 4100 (1) : 47-52

Gephyrocharax martae Dahl, 1943

( Figs. 20– 21 )

Gephyrocharax martae Dahl, 1943: 218 –220, unnumbered fig. on page 5 [original description based on single specimen, holotype MZLU L939/3703, type locality: “Rio Batatal, tributary of Rio San Jorge, Magdalena system. Municipio of Ayapel, department of Bolivar, Republic of Colombia. Altitute approx. 800 m (= Colombia: Córdoba department, Municipio of Montelíbano, Magdalena River basin, Batatal or Ur River, tributary of San Jorge River, approximate altitude 800 m)]. Mojica, 1999: 557 [listed from Colombia, data compilation]. Weitzman, 2003: 224 [catalogue]. Maldonado- Ocampo, Vari & Usma, 2008: 181 [listed from Colombia]. Álvarez-León, Orozco-Rey, Páramo-Fonseca & Restrepo- Santamaría, 2013: 101 [listed from Colombia]. Vanegas-Ríos, Azpelicueta, Mirande & Gonzales, 2013: 282 [examined material, holotype catalogue number as ZMUL]. Thomaz, Arcila, Ortí & Malabarba, 2015: Add. File 5 [tentative classification].

Gephyrocharax marthae . Dahl, 1971: 134 –135, unnumbered figure on page 135 [listed, key, distribution data, name misspelled]. Bonilla-Rivero & López-Rojas, 2013: 489, fig. 1 [distribution map, name misspelled].

Diagnosis. Gephyrocharax martae differs from its congeners by the snout to pectoral-fin length (20.7 % SL vs. 22.8–31.2 % SL), the posteriormost unbranched anal-fin ray of adult male more expanded in sagittal plane than the anteriormost branched anal-fin ray (vs. posteriormost ray expanded in sagittal plane as the anteriormost branched ray), the anal-fin length (61.6 % SL vs. 13.2–25.2 % SL), the seven anterior branched anal-fin rays of adult male very developed, posteriorly projected beyond the midlength of fin (vs. these anal-fin rays not projected beyond the midlength of fin), the presence of a lobe on the posteroventral margin of the pouch scale in adult male, with numerous convergent radii (vs. lobe absent or, when present, radii not convergent to it), and five maxillary teeth (vs. 0–3, except in G. atracaudatus with 1–4 and G. intermedius with 1–5). The absence of bony hooks on caudalfin rays also distinguishes G. m a r t a e from all its congeners (vs. presence of bony hooks). From almost all its congeners, except G. melanocheir and G. t o r re s i, G. m a r t a e is differentiated by the presence of a small dark pigmented area on the last distal third of the outermost branched pectoral-fin ray of adult male (vs. absence of this pigmentation pattern). The possession of a terminal lateral line tube between caudal-fin rays 10 and 11 (vs. absence of this tube) also distinguishes the species from G. melanocheir , G. t o r re s i, and G. v a l e n c i a. Additionally, G. martae differs from G. atracaudatus , G. caucanus , G. chocoensis , G. intermedius , G. major , and G. venezuelae by the gillgland size of adult male (6.4 % SL vs. 0.5–5.4 % SL).

Description. Based on holotype, single specimen currently known. Morphometric data in Table 6 . Male 34.5 mm SL. Body laterally compressed, with maximum depth at vertical through pelvic-fin origin. Dorsal profile of head somewhat convex from margin of upper lip to distal tip of ascendant process of premaxilla, and straight from this point to tip of supraoccipital spine. Dorsal profile of body slightly convex from posterior end of supraoccipital spine to dorsal-fin origin, slanting posteroventrally along dorsal-fin base, and straight from posteriormost dorsalfin ray to caudal peduncle ( Fig. 20 ). Ventral profile of body convex from tip of dentary to pectoral-fin origin, slightly concave between this point and anal-fin origin, slanting posterodorsally and straight from this point to caudal peduncle origin. Anterior fontanel reduced to narrow opening anterior to epiphyseal bar. Anterior nostril rounded, separated by skin fold from larger posterior nostril. Two grooves on head with neuromasts, but poorly preserved in holotype; larger groove extending from half-length between posterior pore of nasal bone and nostrils to posterior portion of frontals; small groove extending between nostrils and nasal bones.

Characters MZLU FMNH Males Females and unsexed juveniles

L939/3703 125572

......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 3, tricuspid teeth. Inner row with 4 teeth; symphyseal tooth tetracuspid, remaining teeth penta- to hexacuspid. Maxilla with 5 teeth ( Fig. 21 A); dorsalmost tooth pentacuspid, middle teeth tricuspid, and ventralmost tooth conical. Maxilla posteriorly reaching vertical through anterior one-third of eye. Dentary with 12 teeth ( Fig. 21 B); three anteriormost teeth larger, pentacuspid, followed by one median-sized tooth pentacuspid, and 9 smaller conical or tricuspid teeth (anteriormost tooth of this series with higher number of cusps).

Dorsal-fin rays ii,8. Nine proximal pterygiophores on dorsal fin (rad). Dorsal-fin origin located at vertical crossing base of fifth anal-fin ray. Adipose-fin origin located at vertical through posteriormost anal-fin ray. Analfin rays v,28. Thirty-two proximal pterygiophores on anal fin (rad). Anal-fin origin closer to origin of hypural joint than to snout tip. Pectoral-fin rays i,10. Pectoral-fin distal tip posteriorly reaching one-quarter of pelvic-fin length. Pelvic-fin rays i,6. Pelvic-fin origin located at vertical on lateral-line scale 10 and anterior to body midlength. Caudal fin forked with 10/9 principal rays in all specimens.

Scales cycloid, with several radii along posterior margin. Lateral line complete, pored scales 40. Terminal lateral-line tube present. Predorsal scales 20. Scale rows between dorsal fin and lateral line 6. Scale rows between lateral line and anal fin 5. Scale rows between lateral line and pelvic fin 4. Circumpeduncular scales 14. One row of 3 large scales forming sheath along anal-fin base. Total number of vertebrae 39; 16 (7), 15 precaudal and 23 caudal (rad). Gill-rakers on dorsal and ventral limbs of first branchial arch severely damaged, counts not taken.

Color in alcohol. Holotype very faded, following color features tentative in waiting of further reassessment based on well-preserved specimens. Ground color pale brown, darker along mid-dorsal line and slightly lighter ventrally. Predorsal region pigmented by minute dark chromatophores. Minute dark chromatophores covering body, except ventral and lateral regions of abdomen and caudal peduncle. Dark midlateral stripe extremely diffuse. Dark chromatophores present along myosepta between lateral line and upper portion of anal fin. Humeral blotch absent. Blotch on caudal peduncle extremely diffuse. Dorsal fin light gray or faint yellow, with few scattered dark chromatophores on membranes. Anal fin light gray and faint yellow, with scattered dark chromatophores located on interradial membranes. Caudal fin light gray, with scattered dark chromatophores on rays. Pectoral and pelvic fins light gray, with few dark chromatophores on rays. Outermost branched pectoral-fin ray with disperse dark pigmentation on its last distal third. Head darker dorsally than ventrally. Opercle, infraorbitals, premaxilla, anterior portion of maxilla, dentary, and lips not pigmented.

Sexual dimorphism. Based on adult male holotype. Male with bony hooks on anal- and pelvic-fin rays. Pelvic-fin rays (unbranched ray broken) with short, slender, anteroventrally positioned hooks on almost entire length of rays; usually one or two per segment. Anal fin with slender, anterolaterally placed hooks with broad bases; from 4 to 11 pairs per ray located on segmented portion of posteriormost unbranched ray and up to five anterior branched rays. Unbranched and seven anterior branched anal-fin rays more flattened sagittally than laterally; posteriormost unbranched ray longer (distal half portion broken but preserved in jar with holotype), but all these rays posteriorly projecting as filament beyond caudal peduncle origin. Anal-fin base of male slightly concave or curved along its midlength. Male with hypertrophied scale forming pouch on lower caudal-fin lobe and with ventral procurrent rays 2 and 3 forming spur-shaped structure ( Figs. 21 C–D). Tissue of glandular appearance not observed. First ventral procurrent ray with a moderate concavity on its ventral margin. Second ventral procurrent ray somewhat longer than third ray, reaching posteriorly midlength of first ventral procurrent ray, and more expanded sagittally than third ventral procurrent ray. Posterior portion of third ventral procurrent ray scarcely developed laterally. Pouch scale with 37 radii located between caudal-fin ray 16 and third ventral procurrent ray. Pouch scale having posteroventral pointed lobe, marked by convergent radii, and extending from third ventral procurrent ray to point between first and second ventral procurrent rays ( Fig. 21 C). 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 lacking notches. Male with gill-gland length of 6.4 % SL; gill filaments damaged, not counted. Female unknown.

Distribution. Gephyrocharax martae is only known from its type locality in the San Jorge River basin, Colombia ( Fig. 1 ).

Remarks. The holotype of G. m a r t a e is currently in a poor state of conservation, being faded and dehydrated. The posteriormost unbranched anal-fin ray, portions of the caudal-fin lobes, and left-side opercle are broken and were carefully illustrated or photographed. Dahl (1943) reported the following color features for the species based on the holotype when it was in a better state of preservation: “ small dark spot on caudal peduncle, not extending on fin, prolonged by black lateral line, terminating above ventrals. Pectoral tipped with black. No Humeral spot. No dark spot at base of first dorsal ray. General colour silvery ”. Consequently, these characteristics, which could be partially observed in the holotype, constitute a better assessment of the color pattern for G. m a r t a e.

The type locality of G. martae was stated by Dahl (1943) as “ …Rio Batatal, tributary to Rio San Jorge, Magdalena system. Municipio de Ayapel, department de Bolivar, Republic de Colombia. Altitude approx. 800 m … ”. According to the political map of Colombia before 1951 (http://www.bolivar.gov.co), the Bolívar department included the currently known as the Sucre and Córdoba departments, whereas the Ayapel county (= “Municipio”) had a larger surface area at that time than it now does. Currently, the Batatal River (also called Uré River) belongs to the geopolitical limits of the Montelíbano county (near Ayapel) flowing from the Corregimiento of Uré across the Cerro Matoso to the Serranía of Ayapel. The upper San Jorge River is approximately defined about 800 m a. s. l. in the Córdoba department. Therefore, the type locality is located in the Corregimiento of Uré, Montelíbano county, southeast of the Córdoba department in the limits with the Antioquia department. The geographic coordinates of the type locality were estimated using the information provided by Dahl (1943), mainly following the river course and the altitude through maps. In the collection data of the holotype label, the collecting date is February 1939 (not informed in the original description).

Recent collecting efforts made on the San Jorge River basin (both middle and lower portions) failed to capture new specimens of G. m a r t a e, instead specimens of G. melanocheir were collected. The upper portion of the river, near Montelíbano, was not visited during these collecting events due to this is an unsafety area. Dahl (1971) commented that G. martae was abundant, occurring in small tributaries of the San Jorge River (where he also recorded G. melanocheir ). The fishes sampled by Dahl (1971) were not found in any of the collections visited during this study. Further expeditions to the upper San Jorge River basin are necessary to know the current conservation status of this possibly threatened species.

Dahl (1971) reported for G. m a r t a e a range between 45 and 47 lateral-line scales in his key of the Gephyrocharax species, which means that the author examined at least one more specimen of the species. Unfortunately, Dahl’s 1971 specimens were not associated to any scientific collection and consequently were not found; it is almost sure that this material is currently lost ( Cala 1987).

Material examined. Colombia: MZLU L939/3703, holotype of Gephyrocharax martae , 34.51 mm SL (rad), [Córdoba, Montelíbano, Uré], Bolívar, Ayapel, Magdalena River basin, Batatal River [or Ur River], tributary of San Jorge River, altitude 800 m, approximately 7°23'10.42"N 76°2'57.78"W, [Feb. 1939, G. Dahl].

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 20. Gephyrocharax martae, male, holotype, 34.5 mm SL, MZLU L 939 / 3703: (A) lateral view of body; (C) middle and distal portions of posteriormost unbranched anal-fin ray. Left side. Scale = 1 mm.

FIGURE 21. Gephyrocharax martae, male, holotype, 34.5 mm SL, MZLU L 939 / 3703: (A – B) upper and lower jaws, right side; (C – D) detail of lower caudal skeleton, associated pouch scale, and posteriormost ventral procurrent rays, left side. 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. Scale = 1 mm.

Tables

TABLE 6. Morphometric data of holotype of Gephyrocharax martae (A), neotype (B) by present designation and other examined specimens of G. melanocheir. Ranges of males including neotype values. M = mean; SD = standard deviation.

	A	B	n	Range	M	DS	n	Range	M	DS
Standard length (mm)	34.5	32.6	59	27.4–39.3	32.8	2.9	74	11.8–41.9	32.7	2.0
Percentages of standard length:
Depth at dorsal-fin origin	28.5	32.9	45	28.5–35.5	32.2	1.7	60	27.4–35.8	32.7	2.0
Snout to dorsal-fin origin	63.2	63.2	44	61.0–67.8	63.5	1.6	54	59.1–69.3	63.9	1.6
Snout to pectoral-fin origin	20.7	28.6	40	26.3–31.2	28.3	1.0	54	23.8–29.7	27.1	1.2
Snout to pelvic-fin origin	46.9	43.9	39	42.7–49.1	45.4	1.5	52	44.3–50.5	47.2	1.6
Snout to anal-fin origin	59.2	57.8	40	56.3–64.4	59.4	1.8	54	57.3–65.6	61.3	2.0
Dorsal fin to pectoral fin length	44.9	44.4	40	44.1–52.0	46.9	1.6	54	44.3–51.6	48.0	1.9