Hemiancistrus guahiborum, Werneke & Armbruster & Lujan & Taphorn, 2005

Werneke, David C., Armbruster, Jonathan W., Lujan, Nathan K. & Taphorn, Donald C., 2005, Hemiancistrus guahiborum, a new suckermouth armored catfish from Southern Venezuela (Siluriformes: Loricariidae), Neotropical Ichthyology 3 (4), pp. 543-548 : 544-548

Hemiancistrus guahiborum , new species Figs. 1–2

Holotype. MCNG 51994 , 106.9 mm SL, Venezuela, Amazonas, río Ventuari at raudales Tencua 56 km ESE of San Juan de Manapiare, 05.04968°, -065.62722°, 20-21 Apr 2004, D. C. Werneke, N. K. Lujan, O. León, & R. Pajua.

Paratypes. Venezuela, Amazonas, río Ventuari - río Orinoco drainage: ANSP 180214 , 4 (1, 89.8 mm SL), AUM 39311, 71 (13, 73.1–98.9 mm SL), CAS 222236 , 4 (1, 82.9 mm SL), CU 90879, 4 (1, 84.1 mm SL), FMNH 116464 , 4 (1, 81.8 mm SL), MBUCV-V 32685 , 4 (1, 80.4 mm SL), MCNG 51995 , 4 (1, 80.2 mm SL), UF 148421, 4 (1, 87.0 mm SL), USNM 382415 , 4 (1, 73.0 mm SL), río Manapiare 14.5 km NW of San Juan de Manapiare, 05.42863°, -066.13616°, 12 Apr 2004, N. K. Lujan, M. H. Sabaj, L. S. de Souza, & D. C. Werneke. ANSP 180215 , 4 (4, 83.7–93.8 mm SL), AUM 39505, 4 (4, 96.8–105.5 mm SL), and MCNG 51997 , 3 (3, 68.5–75.5 mm SL), same data as Holotype. ANSP 180216 , 1 , AUM 39282 34 (28, 51.6-93.3 mm SL), MCNG 51998 , 8 , río Parucito at raudales Salomon 2.7 km NE of San Juan de Manapiare,05.34637°, -066.03347°, 16Apr 2004, D. C.Werneke, N. K. Lujan, & O. León. ANSP 180217 , 1 , AUM 39239 8 (8, 69.5-125.53 mm SL), MCNG 51996 , 2 , río Ventuari bedrock outcrop 83 km ENE of Macuruco 153 km ENE of San Fernando deAtabapo, 04.25346°, -066.34466°, 6 Apr 2004, N. K. Lujan, D. C. Werneke, M. H. Sabaj, L. S. de Souza, & O. León. ANSP 180223 , 7 , AUM 42211, 13 , MCNG 52926 , 7 , río Ventuari near ornamental fish market in the river, 04.07565°, -066.89285°, 3 Apr 2005, N. K. Lujan, M. Arce, E. L. Richmond, M. B. Grant, & T. E. Wesley. AUM 37979, 1 (1, 91.7 mm SL), río Guapuchi first major riffle complex, 04.11667°, -066.76667°, 16April 2003, N. K. Lujan & O. León. AUM 39541, 1 (1, 104.5 mm SL), río Ventuari at raudales Tencua 56 km ESE of San Juan de Manapiare,05.04968°, -065.62722°, 20Apr 2004, D. C.Werneke, N. K. Lujan, O. León, & R. Pajua. UF 77850 , 16 (5, 70.9–101.7 mm SL), 2 c&s, río Ventuari at Tencua just below Tencua Falls , 20 Mar 1981, C. R. Gilbert and S. Reid .

Non-type material. VENEZUELA, Amazonas, río Casiquiare - río Negro drainage : ANSP 180220 , 3 , AUM 42178, 4 , MCNG 52927 , 3 , río Siapa rapids 154 km E of San Carlos de río Negro , 01.60339°, -065.71587°, 11 Mar 2005 . ANSP 180221 , 5 , AUM 42183, 8 , MCNG 52928 , 5 , río Siapa raudales Gallineta 142 km E of San Carlos de río Negro , 01.81679°, -065.79473°, 17 Mar 2005 . ANSP 180222 , 2 , AUM 42200, 4 , MCNG 52929 , 1 , río Casiquiare 153 km NE of San Carlos de río Negro , 02.79877°, -066.00652°, 24 Mar 2005 . AUM 42129, 3 , río Casiquiare bedrock in stream 73 km NE of San Carlos de río Negro , 02.35258°, -066.57521°, 9 Mar 2005 . MCNG 26074 , 1 (1, 92.4 mm SL), río Siapa 176 river km from the río Casiquiare , 01.41667°, -065.68333°, 14 Apr 1991 . MCNG 26124 , 1 (1, 94.8 mm SL), río Siapa from 10–15 km below coordinates, 01.50000°, -065.71667°, 20 Apr 1991 . MCNG 37045 , 2 (2, 100.0–106.5 mm SL), base camp on río Siapa below raudal Gallineta, 11 Jan 1998 . MCNG 37063 , 1 (1, 83.7 mm SL), río Siapa immediately below raudal Gallineta, 01.81667°, -065.78333°, 14 Jan 1998 . MCNG 38319 , 1 (1, 98.0 mm SL), base camp on río Siapa below raudal Gallineta, 11 Jan 1998 . Río Orinoco drainage: ANSP 162173 , 5 (9, 66.0–87.0 mm SL), 2 c&s, río Orinoco at rocks circa 1 km above La Esmeralda, 14 Mar 1987 . ANSP 162177 , 26 (5, 33.4–38.6 mm SL), río Orinoco raudales de Atures at Culebra circa 7 km S of Puerto Ayacucho, 11 Nov 1985 . ANSP 180218 , 2 , AUM 42116, 3 , MCNG 52930 , 1 , río Orinoco 117 km W of La Esmeralda, 03.28998°, -066.60004°, 29 Mar 2005 . ANSP 180219 , 3 , AUM 42123, 7 , MCNG 52931 , 3 , río Orinoco 33.9 km W of La Esmeralda at Punto Piaroa, 03.14744°, -065.85381°, 28 Mar 2005 . AUM 42093, 2 , río Orinoco beach 16.1 km E of La Esmeralda, 03.15842°, -06569482°, 25 Mar 2005 . AUM 42103, 1 , río Orinoco beach and bedrock outcropping 50 km E of San Fernando de Atabapo, 03.97029°, -067.25506°, 2 Mar 2005 . AUM 42166, 1 , río Orinoco bedrock outcrop 52.9 km SE of San Antonio 102 km W of La Esmeralda, 03.10036°, -066.46277°, 4 Mar 2005 . AUM 42192, 2 , río Orinoco Punto de Maraya 80.8 km W of San Fernando deAtabapo at Isla Maraya , 04.02303°, -066.97189°, 31 Mar 2005 . AUM 42941, 2 (1, 69.6 mm SL), río Orinoco at Puerto Venado 4.3 km S of Samariapo 56,4 km SSW of Puerto Ayacucho, 05.21060°, - 067.80495°, 26 Feb 2005 . MCNG 25793 , 6 (4, 58.4–86.1 mm SL), 1 c&s, río Ocamo en raudal Arata, 03.13333°, -064.56667°, 24 Jan 1980 . MCNG 47576 , 2 (2, 93.5–107.4 mm SL), río Orinoco rocks near Macuruco , 23 Sep 2002 . MCNG 47577 , 1 (1, 122.3 mm SL), río Orinoco rocks near Macuruco , 23 Sep 2002 . VENEZUELA, Bolivar, río Caura – río Orinoco drainage: ANSP 149689 , 13 (5, 36.5–77.6 mm SL), Surapire Rapids on río Caura circa 2 hrs upstream from río Caura– río Nichare junction, 23 Jan 1977 . MCNG 20878 , 3 (5, 58.3–87.4 mm SL), 2 c&s, río Nichare at a creek behind a small island, 06.22917°, -064.93861°, 19 Mar 1989 . MCNG 22521 , 3 (3, 53.3–91.0 mm SL), upper río Nichare , on a beach above caño Icutú, 06.81944°, -064.91667°, 15 Mar 1989 . MCNG 22701 , 5 (4, 75.9–114.8 mm SL), 1 c&s, caño Tabaro tributary of río Nichare , 06.36667°, -064.96667°, 21 Mar 1989 . MCNG 22795 , 1 (1, 42.2 mm SL), caño Tabaro in a stream entering the Serrania, 22 March 1989 . MCNG 22867 , 7 (7, 49.8–83.1 mm SL), 1 c&s, upper río Nichare , 06.87500°, -064.93417°, 18 Mar 1989 . MCNG 22933 , 1 (1, 70.6 mm SL), caño Tabaro to 3 km from río Nichare , 06.36667°, -064.96667°, 25 Mar 1989 . río Orinoco drainage: ANSP 162176 , 2 (2, 51.9–105.3 mm SL), río Orinoco at El Burro, 06.20000°, - 067.43333°, 26 Nov 1985 .

Diagnosis. Hemiancistrus guahiborum can be separated from all other Hemiancistrus and all Peckoltia except P. braueri and P. cavatica by having an orange edge to the dorsal and caudal fins ( Fig. 1). Hemiancistrus guahiborum can be separated from the H. annectens group of Armbruster (1998) ( H. annectens , H. aspidolepis , H. holostictus , H. maracaiboensis , H. panamensis , and H. wilsoni ), H. fuliginosus , H. hammarlundi , H. landoni , H. medians , H. megalopteryx , H. micrommatos , H. punctulatus , H. spilomma , H. spinosissimus , P. oligospila , P. sabaji , and P. snethlagae by having large tan blotches on a dark body with the blotches sometimes faded so that the body is entirely dark (vs. with black spots); from H. chlorostictus and H. votouro by having large light blotches (vs. small white spots); from H. chlorostictus , H. meizospilos , and H. votouro by having a forked caudal fin (vs. an emarginate caudal fin); from H. macrops by having the white markings diffuse (vs. discreet spots); from the H. annectens group by having more than 10 relatively straight hypertrophied odontodes on the evertible cheek plates (vs. usually less than five strongly recurved hypertrophied odontodes); and from the remainder of Peckoltia by having the dorsal fin with light spots or uniformly colored and the sides either solidly colored or with tan blotches (vs. dorsal fin with bands or dark spots and sides with saddles dorsally).

In addition Hemiancistrus guahiborum can be separated from all ancistrins except Baryancistrus , other Hemiancistrus , Hypancistrus , Panaque , Parancistrus , Peckoltia , and some Pseudancistrus by lacking odontodes on the opercle; from Ancistrus , Dekeyseria , Lasiancistrus , Neblinichthys , and Pseudolithoxus by having five rows of plates on the caudal peduncle (vs. three); from Hopliancistrus by having more than five hypertrophied odontodes on the evertible cheek plates; from Exastilithoxus and Lithoxus by having 28 or more teeth per jaw ramus (vs. 10 or fewer) and oval lips (vs. round); from Acanthicus , Chaetostoma , Cordylancistrus , Dolichancistrus , Leptoancistrus , Leporacanthicus , Megalancistrus , and Pseudacanthicus by having seven dorsal-fin rays (vs. eight or more); from Acanthicus , Dekeyseria , Leporacanthicus , Megalancistrus , and Pseudacanthicus by lacking keels on the lateral plates; from most Pseudancistrus by lacking hypertrophied odontodes around the snout; from Pseudancistrus sidereus and P. megacephalus by having diffuse spots when present (vs. round spots); from Baryancistrus by not having the posterior portion of the dorsal-fin membrane expanded; from Parancistrus , Spectracanthicus , and most Baryancistrus by not having the dorsal fin connected to the adipose fin; from Panaque by having viliform teeth (vs. spoon-shaped teeth or elongated teeth); and from Hypancistrus by having the teeth of the dentary and premaxillary of equal size (vs. dentary teeth longer than premaxillary teeth).

Description. Member of Hypostominae , Ancistrini as diagnosed by Armbruster (2004). Morphometrics in Table 1. Medium-sized loricariids, largest specimen 125.5 mm SL. Body stout. Head sloped at 45° angle to point above anterior portion of eye. Nape ascending slightly to insertion of dorsal fin. Dorsal slope decreasing to insertion of dorsal procurrent caudal rays then ascending to caudal fin. Body depth greatest below anterior insertion of dorsal fin. Ventral profile flat to caudal fin. Caudal peduncle triangular in cross section with dorsal surface slightly rounded. Body widest at insertion of pectoral fins, narrowest at insertion of caudal fin. Snout rounded.

Eyes moderately sized. Interorbital space flat. Slight ridge formed between anterodorsal margin of orbit and nares. Supraoccipital pointed posteriorly, not elevated above nuchal plate. Infraorbitals, frontal, nasal, pterotic-supracleithrum, and supraoccipital supporting odontodes. Preopercle and opercle not supporting odontodes.

Lips covered with short, wide papillae. Lower lip wide, upper lip narrow. Maxillary barbel only barbel present, reaching one third of distance to gill opening. Iris with small dorsal flap.

Medial plates 22–26 (mode = 24). Plates unkeeled. Five caudal peduncle plate rows. Plates on all surfaces of body except for anteroventral margin of snout, throat, and abdomen from pectoral girdle to anus. Some small embedded plates ventral to pectoral girdle and along ventromedial insertion of pectoral fin. Evertible cheek plates supporting hypertrophied odontodes that can be everted perpendicular to head. Cheek odontodes 9–84 (mode = 45); number of cheek odontodes increases ontogenetically. Longest evertible cheek odontode reaching cleithrum. Hypertrophied cheek odontodes relatively weak. Moderately hypertrophied odontodes present along dorsal-, adipose-, pelvic-, caudal-, and pectoral-fin spines; larger individuals with hypertrophied odontodes at tip of pectoral spine.

Dorsal fin II,7; dorsal-fin spinelet V-shaped, dorsal-fin locking mechanism present, dorsal fin free from adipose fin, distal margin of dorsal fin reaching insertion of adipose spine when adpressed. Adipose fin with single preadipose plate and moderately long spine. Caudal fin i,14,i; caudal fin forked, lower lobe longer than upper, dorsal and ventral procurrent caudal rays four to five (mode four). Pectoral fin I,6; pectoral-fin spine reaching beyond insertion of pelvic-fin spine when adpressed ventral to pelvic fin. Pelvic fin I,5; adpressed pelvic-fin spine extending beyond base of anal fin. Anal fin I,4; anal-fin spine slightly shorter than first ray.

Teeth bicuspid with median lobe one third longer and twice as wide as lateral lobe. Worn teeth with lobes approaching equal lengths. 30–64 left dentary teeth (mode = 43). 28–72 left premaxillary teeth (mode = 39).

Color in Life. Base color of head and body mottled gray and tan, with dermal plates outlined with dark gray. Pattern irregular and varies among individuals, but between and behind eyes tan spots are smaller and rounded. Behind dorsal fin, upper half of flank gray with irregular tan blotches, lower half of flank mostly tan. Lips tan. Eye light reddish-brown. Dorsal fin with smoky charcoal membranes, spine gray on anterior margin but tan laterally, not spotted; rays with series of gray and tan blotches, more or less aligned to form alternating rows with three or four gray blotches of each contrasting color; fin edged with very thin margin of brick red or orange, wider on first three or four rays. Adipose fin tan with distal gray edge. Caudal-fin rays dark gray, membranes in between transparent, basal plate on base of fin gray; distal margin edged with orange, widest on upper rays. Pectoral fin spine gray, rays tan, sometimes spotted. Pelvic-fin spine and rays tan on distal two thirds of fin, dark gray on distal third. Abdomen tan to cream.

Color in alcohol. Base color brown or gray ( Figs. 1–2). Small faint light gray-tan spots on head, becoming larger and more irregularly shaped on body. Sizes of spots vary between individuals and absent in some specimens. Dorsal-fin spine lacking spots. Dorsal-fin rays and membranes typically with spots, spots on dorsal-fin membranes difficult to discern in some specimens. Adipose-fin spine with only one or two spots if present, membrane dusky. Caudal fin dusky, occasionally with lighter narrow bands in some specimens. Pectoral and pelvic fins sometimes with spots dorsally, rays and membranes lacking spots dusky. Anal fin dusky near insertion, fading distally. Lips, barbels, and throat tan. Small embedded plates below pectoral girdle gold. Venter behind pectoral girdle to anus translucent white, internal musculature and organs visible through skin. Venter behind anus tan with scattered melanophores.

Range. Found in middle and upper río Orinoco and its tributaries including the río Caura, río Ventuari, and río Ocamo, also found in río Casiquiare ( Fig. 3).

Etymology. Named for the Guahibo, a tribe of people inhabiting parts of southern Venezuela and western Colombia for the help some members of the tribe provided in collecting specimens in the upper río Ventuari.

Gut Morphology and Ecology. Gastrointestinal tract brown with yellow fat deposits loosely attached to intestinal wall with viscera packed tightly into peritoneal cavity. Esophagus turns 90° to right upon entering the peritoneal cavity, extends short distance (~ 10 mm in specimens examined), then turns 90° to posterior before transitioning into stomach. Stomach extends straight to posterior for two thirds of total stomach length then turns 180° to right for final one third. Length of stomach 15 mm.Volume of stomach highly variable. From stomach, intestines turn 90° to left, crossing dorsally over esophagus, then turn 90° to posterior, continuing towards anus. Proximal and distal portions of intestine spiral clockwise in parallel, with coils accruing ventral to stomach. Total length of intestines plus stomach ranged from 15–18 times SL. External diameter of intestines ranged from 1.0–1.5 mm.

Hemiancistrus guahiborum were most frequently encountered in cracks and interstitial spaces of granitic and lateritic rocks in flow. Gut contents of all individuals consisted largely of small grained (<0.001mm diameter) mineral matrix. Identifiable organic material embedded in the gut matrix of three individuals surveyed was limited to midge larvae ( Chironomidae , n=3), a fly pupa ( Diptera , n=1), an unidentified insect exoskeleton (n=1), and a shed tooth (n=1).