Ancistrus gymnorhynchus Kner 1854
Creators: name: Taphorn, Donald C.
name: Armbruster, Jonathan W.
name: Rodríguez-Olarte, Douglas
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Siluriformes
Loricariidae
Ancistrus
Ancistrus gymnorhynchus

description: Ancistrus gymnorhynchus Kner, 1854
Figures 1 and 2. Table 1.
Ancistrus gymnorhynchus Kner, 1854:275. Type locality: Puerto Cabello [Venezuela, approximately 10o 28’ N, 68o 00’ W]. Holotype: NMW 43495. Originally as Anc. gymnorhynchus. Steindachner 1917:93, pl. 9, figs. 7–8, redescription of holotype. Schultz 1944:305 synonymy with Xenocara rothschildi. Mago L. 1970: (list). Fisch Muller in Reis et al. (2003:376), summary of status. Lasso et al. 2004a:131 (list of Orinoco Basin species). Lasso et al. 2004b:172; Rodríguez-Olarte et al. 2009:75 (list).
Hypostomus karstenii Lütken (ex Kröyer), 1874: 204. Not available, name published in the synonymy of Chaetostomus gymnorhynchus (Kner, 1854).
Xenocara rothschildi Regan, 1905: 242. Type locality: San Esteban, near Puerto Cabello, Venezuela. Syntypes: BMNH 1904.11.9.27–31 (5).
Lasiancistrus nationi Fernández-Yépez 1972:23, Pl. 23 Type locality: Río Yaracuy drainage, Venezuela: Holotype and paratypes were lost along with most of the personal collection of AFY. Lasso et al. 2004b:174 (list).
Ancistrus nationi Rodríguez-Olarte et al. 2006a:110 (list), Rodríguez-Olarte et al. 2007: 43 (list).
Diagnosis. Ancistrus gymnorhynchus differs from Venezuelan congeners in having an unspotted color pattern of gray, brown or tan. Although it does have a black spot or dark area at the base of the first dorsal-fin membrane, it lacks either dark or light spots on the remainder of that and all other fins, as well as the dorsum, sides and abdomen (we have observed light colored spots in a few individuals of only one population of A. gymnorhynchus, from near Totoremo, middle Tocuyo River) in preserved specimens. A few live specimens have been observed with faint light spots on the dorsum, but these disappear upon preservation. Within its known range of distribution, it might occur with Ancistrus triradiatus, which has rows of black spots on the dorsal and caudal fins. Ancistrus martini occurs in the Maracaibo Basin to the west of the range of A. gymnorhynchus and is easily distinguished by having rows of dark spots on the dorsal and caudal fins, and a dark abdomen with large bold white spots or vermiculations. Ancistrus brevifilis occurs in the Tuy River drainage just to the east of A. gymnorhynchus, and is distinguished by dark fins with light colored spots. See the diagnosis of A. falconensis n. sp. described below for morphological differences.
Description. Morphometrics are given in Table 1. Head and body robust but relatively narrow, greatest body depth near dorsal-fin origin. Greatest width of body between opercles and pectoral-fin origins, then narrowing progressively to end of caudal peduncle. Dorsal profile of head and body convex from tip of snout tip to dorsal-fin origin, from there, nearly straight and sloping gradually down to dorsal procurrent caudal-fin rays, then angled dorsally ~45o to caudal fin. Ventral profile convex from tip of snout to below pectoral-fin insertions, abdomen slightly concave to pelvic-fin insertions, from there, straight and sloping gently up towards caudal fin. Caudal peduncle deep and robust. Snout broadly rounded with large broad naked margin in males, less developed in females and juveniles. As in all species of Ancistrus the tentacles are better developed in males (Figure 1) and present in all areas defined by Sabaj et al. (1999): cheek, posterior and anterior margins, anteromedial and posteromedial regions of the unplated snout. Tentacles absent in females, or if present much smaller and only along posterior and anterior snout margins. Eye moderate, dorsal margin of orbit not elevated, interorbital area slightly concave.
Hypertrophied cheek odontodes eight to 17 (mode 12), stout with tips hooked anteriorly, strongly evertible, the longest reaching beyond pectoral fin insertion, bases encased in thick fleshy sheaths. Oral disk slightly ovate, wider than long. Lips covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching pectoral girdle, its border covered with very small papillae. Maxillary barbel short, slightly longer than buccal papilla. Dentary tooth row curved, slightly narrower than premaxillary tooth row. Teeth unevenly bifid, medial cusp much larger and spatulate, lateral cusp minute and pointed, usually not reaching more than half length of medial cusp, but equal in worn teeth.
Exposed part of opercle roughly triangular and bearing short stout odontodes. Three to five dermal plates present in postopercular area. Supraoccipital with margins between surrounding bones and plates usually clearly visible. Nuchal plate small and curved posterolaterally. Five series of lateral plates anteriorly, middorsal and mid-ventral plate series end on caudal peduncle. Mid-dorsal plates 10(1),14(2) 15(8) 16(17), 17(19), 18(17), 19(2); median plates 21(5), 22(38), 23(23); mid-ventral plates 16(8), 17(35), 18(22), 19(1); plates bordering dorsal-fin base 6(39), 7(26), 8(1); plates between dorsal and adipose fins 6(23), 7(43); preadipose plates: 1(63), 2(3). Mid-dorsal and mid-ventral plate series ending at point near vertical through adipose-fin origin. Last plate in median series slightly smaller than penultimate plate, base of caudal fin with about four small platelets after main series, then about eight roughly triangular platelets covering bases of caudal-fin rays. Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays. Abdomen entirely devoid of plates; no exposed platelets anterior to anal-fin spine.
Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion. Dorsal fin short, tip of adpressed fin falling just short of single median preadipose plate. Adipose fin with stout spine and welldeveloped adnate membrane that adheres to plate just anterior to first procurrent caudal-fin ray. Pectoral spine long and slender, extending to middle of pelvic spine. Anal fin well developed, short; first anal-fin pterygiophore covered by skin. Caudal fin with straight oblique posterior margin, spines and first dorsal and ventral rays slightly longer than others, base not visible as plate-like structure. Ventral caudal-fin ray extends posteriorly following horizontal profile of caudal peduncle, not angled downward. Fin-ray formulae (N=66): dorsal i,7; pectoral i,6; pelvic i,5; anal i,4; caudal i,14,i. Caudal procurrent spines: dorsal: 5(64), 4(2) ventral: 3(45), 4(20), 5(1).
Color in alcohol. Body gray, brown or tan, without dark or light spots; some plates outlined with lighter or darker tones. Ventral portions of head, abdomen and caudal peduncle usually paler, not spotted. The one observed exception is in two specimens from Totoremo, in the middle Tocuyo River drainage, where we observed light spots on the abdomen. In nearby localities of the same tributary no spots were observed. Morphologically these two specimens grouped with A. gymnorhynchus in the PCA analysis. Dorsal fin usually with black pigment at base of first membrane. Caudal fin sometimes very dark gray. A few specimens have numerous inconspicuous pale spots on rays of paired fins upon close inspection. Lips cream color or light gray to whitish.
Distribution. (Figure 2.) South America: central Venezuela: coastal rivers of Falcón, Lara, Yaracuy and Carabobo States. An all brown color morph (vs. gray) has been found in the Chirgua River and tributaries (upper Pao River drainage) in Cojedes state. This is the only population known from the Orinoco River Basin.
Specimens examined. We examined photographs of the holotype of Ancistrus gymnorhynchus NMW 43495.
The following lots include specimens of Ancistrus gymnorhynchus that were counted and measured for Table 1: (All from Venezuela) INHS: 28865, 2, Lara, Río Curarigua at bridge, (Puente Torres), 6 January 1993, D. Taphorn, L. Page, K. Cummings, C. Mayer, P. Ceas, J. Armbruster, C. Laird and M. Sabaj; 28906, 3, Yaracuy, tributary of Río Yaracuy, East of Marin, 7 January 1993, D. Taphorn, L. Page, K. Cummings, C. Mayer, P. Ceas, J. Armbruster, C. Laird and M.H. Sabaj; 28921, 5, Carabobo, Río Capa, Canoabo, 10° 18' N, 68° 17' W, 7 January 1993, D. Taphorn, L. Page, K. Cummings, C. Mayer, P. Ceas, J. Armbruster, C. Laird and M. Sabaj; 34951, 1, Falcón, Río Aroa, Palma Sola, 10° 35' 58" N, 68° 33' 03" W, 21 January 1995, D. Taphorn, L. Page, K. Cummings, C. Mayer, P. Ceas and J. Armbruster; 60097, 4, Yaracuy, Río Tupe, ca. 12 km N of Aroa on highway 3, 10 ° 30.31' N, 68° 52.55' W, 31 December 1990, D. Taphorn, L. Page, P. Ceas and M. Retzer; 60122, 4, Yaracuy, Río Guarataro, Carabobo, 10° 34' N, 68° 44' W, 30 December 1990, D. Taphorn, L. Page, P. Ceas and M. Retzer. CPUCLA: 442, 1, Yaracuy, río Guarataro, Aroa, Sector Guaratarito, 15 km SE of Carabobo, Yumare-Aroa highway, 0 5 July 2002, D. Rodríguez-O, J. Coronel, A. Amaro, E. Lucena, J. Lopéz, A. Pichardo; 1018, 1, Yaracuy, Río Carabobo-Aroa, upstream of Barlovento, Aroa- Carabobo highway, 15 January 2004, D. Rodríguez-Olarte, A. Amaro; 1741, 4, Carabobo, río Alpargatón- Urama, Urama-Moron highway, Sector Alpargaton, 2 km from the entrance of the sand extraction plant, 20 April 2006, D. Rodríguez-O, A. Amaro, H. Agudelo; 1870, 1, Falcón, río Totoremo-Tocuyo, Totoremo village, 10 November 2006, D. Rodríguez-Olarte, A. Amaro, J. L. Coronel, H. Rivera, H. Agudelo; 1871, 1, Falcón, río Cararapa-Tocuyo, Cararapa village, 10 November 2006, D. Rodríguez-Olarte, D. Rodríguez- Olarte, D. Taphorn, A. Amaro, J. L. Coronel, H. Agudelo and H. Rivera; 1872, 2, Carabobo, río Alpargatón- Urama, Urama-Moron highway, Sector Alpargaton, 2 km from entrance to sand extraction plant, 0 1 November 2006, D. Rodríguez-Olarte, D. Taphorn, A. Amaro, J. L. Coronel, H. Agudelo and H. Rivera; 1873, 2, Yaracuy, Quebrada Guáquira, Cerro Zapatero, 0 7 November 2006; D. Rodríguez-Olarte, D. Taphorn, A. Amaro, J. L. Coronel, H. Agudelo and H. Rivera; MCNG 14257, 80, Cojedes, Río Chirgua, between Tinaquillo and Campo Carabobo, 09° 58' 20"N, 68° 12' 40"W, 4 August 1985, D. Taphorn et al.; 15289, 15, Carabobo, Río Chirgua, tributary of Río Pao, 10° 08' 30"N, 68° 11' 30"W, 19 October 1985, D. Taphorn et al.; 24543, 9, Carabobo, Río Chirguita at the bridge, 23 December 1990, M. Retzer et al.; 24660, 9, Carabobo, Río Capa in Canoabo (tributary of Río Urama). 10° 18' 00"N, 68° 17' 00"W, 30 December 1990, D. Taphorn et al.; 24661, 2, Yaracuy, Creek in Guayabito, at the bridge, 10° 28' 00"N, 68° 39' 00"W, 31 December 1990, D. Taphorn et al.; 24694, 4, Yaracuy, Río Tupe, N of Aroa, 01° 30' 31"N, 68° 52' 55"W, 31 December 1990, D. Taphorn et al.; 24713, 7, Yaracuy, Río Guarataro between Aroa and Yumare, at bridge, 10° 34' 00"N, 68° 44' 00"W, D. Taphorn et al., 27620, 3, Yaracuy, Río Yurubí near entrance to Guayabito 10° 29' 08"N, 68° 39' 40"W, 7 January 1993; 27625, 5, Carabobo, 10° 18' 49"N, 68° 16' 55"W, Creek in Canoabo, 7 January 1993; 32117, 4, Yaracuy, Caripial Creek, Aroa dr., at bridge SE of Yumare 10° 33' 42"N, 68° 37' 37"W, 21 January 1995 D. Taphorn et al.; 32120, 3, Falcon, Creek called ”El 26” or Minapo, Aroa dr., north of Palma Sola 10° 36' 48"N, 68° 33' 46"W, 21 January 1995, D. Taphorn et al.; 52073, 3, Yaracuy, Río Carabobo, sector Barlovento, 15 January 2004, D. Rodriguez et al.; 54572, 16, Carabobo, El Samán en el río Alpargatón, 10° 15' 13"N, 68° 15' 45"E, 21 October 2005, D. Taphorn et al.; 54593, 13, Yaracuy, Stream on Hacienda Guáquira, 21 October 2005, D. Taphorn et al.; 54614, 7, Yaracuy, Sarare Creek, 1 km from Hacienda Corozal, 23 October 2005, D. Taphorn et al.
The following material examined was not measured but was used for the distribution map: MCNG 14068, 2, Yaracuy, Quebrada Cupa, near Aroa, 10° 29' 50"N, 68° 52' 20"W, 7 July 1985, D. Taphorn et al.; 25079, 4, Lara, creek at bridge SE of Goajira near Las Palmas, 11 January 1991, D. Taphorn et al.; 25090, 1, Lara, Río Tocuyo at bridge (Puente Torres), old highway, 12 January 1991, D. Taphorn et al.; 27590, 1, Lara, Río Curarigua at bridge on highway 12, between Carora and Barquisimeto, 10° 04' 07"N, 69° 56' 19"W, 6 January 1993, D. Taphorn et al.; 27609, 1, Yaracuy, Río Yurubí near Guayabito, 10° 29' 08"N, 68° 39' 40"W, 1 July 1993, D. Taphorn et al.; 49643, 3, Yaracuy, Río Crucito, Marin-Yumare Hwy., 10° 33' 39"N, 68° 37' 37"E, 4 February 2001, D. Rodríguez O. et al.; 49657, 1, Yaracuy, Río Tesorero, sector Santa Rosa, 4 February 2002, D. Rodríguez O. et al.; 52088, 1, Yaracuy, Río Crucito, 1 km from Guayabito bridge, 16 March 2004, D. Rodríguez O. et al.; 55731, 14, Yaracuy, Río Urama, Urama – Moron Hwy., sector Alpargaton, 11 November 2006, D. Rodríguez O. et al.
description: Published as part of Taphorn, Donald C., Armbruster, Jonathan W. & Rodríguez-Olarte, Douglas, 2010, Ancistrus falconensis n. sp. and A. gymnorhynchus Kner (Siluriformes: Loricariidae) from central Venezuelan Caribbean coastal streams, pp. 19-32 in Zootaxa 2345 on pages 21-25, DOI: 10.5281/zenodo.193371