Baryancistrus demantoides, Werneke & Sabaj & Lujan & Armbruster, 2005

Werneke, David C., Sabaj, Mark H., Lujan, Nathan K. & Armbruster, Jonathan W., 2005, Baryancistrus demantoides and Hemiancistrus subviridis, two new uniquely colored species of catfishes from Venezuela (Siluriformes: Loricariidae), Neotropical Ichthyology 3 (4), pp. 533-542 : 535-537

Baryancistrus demantoides , new species Figs. 1a,b and 2

Holotype. MCNG 54029, 150.5 mm SL, Venezuela, Amazonas, río Orinoco drainage, río Ventuari near ornamental fish market in river, 04.07565°, -066.89285°, 3 Apr 2005, N. K. Lujan, M. Arce, E. L. Richmond, M. B. Grant, & T. E. Wesley.

Paratypes. Venezuela, Amazonas, río Orinoco drainage: AUM 37974, 1 (1, 131.5 mm SL), río Guapuchi first major riffle complex, 04.11667°, -066.76667°, 16 Apr 2003, N. K. Lujan & O. León. ANSP 180226 , 1 (1, 85.5 mm SL), AUM 42034, 1 (1, 96.3 mm SL), MCNG 54030 , 1 (1, 50.6 mm SL), río Orinoco , Cucue Amerindian Village 60 km E of San Fernando de Atabapo, 03.97380°, -067.15821°, 3 Apr 2004, M. H. Sabaj, N. K. Lujan, D. C. Werneke, & L. S. de Souza. ANSP 180227 , 1 (1, 88.3 mm SL), AUM 42204, 1 (1, 124.8 mm SL), same data as holotype. ANSP 180228 , 1 (1, 115.4 mm SL), AUM 42169, 2 (2, 103.8– 118.3 mm SL), 1 c&s, MCNG 54031 , 1 (1, 54.1 mm SL), río Orinoco 60 km E of San Fernando de Atabapo, 03.97401°, - 067.16276°, 3 Mar 2005, N. K. Lujan, D. C. Werneke, M. H. Sabaj, & M. Arce .

Diagnosis. Baryancistrus demantoides can be distinguished from all other loricariids except Baryancistrus niveatus , Parancistrus , and Spectracanthicus by having the dorsal and adipose fins connected by an expanded posterior section of the dorsal-fin membrane. Baryancistrus demantoides can be separated from the other species with connected dorsal fins by having a yellow-olive color with white or creamcolored spots (vs. typically dark with white, gold, or no spots); from other Baryancistrus with the dorsal fins connected by having the spots only on the anterior portion on the body (vs. all over), from Parancistrus by not being dorsoventrally flattened, and from Spectracanthicus by having greater than 30 teeth per jaw ramus (vs. less than 25). There is one other described species of Baryancistrus ( B. longipinnis ) that has an expanded posterior membrane of the dorsal fin, but the membrane does not connect to the adipose fin as in B. demantoides and B. longipinnis lacks light spots.

Description. A member of Subfamily Hypostominae , Tribe Ancistrini as diagnosed by Armbruster (2004). Morphometrics presented in Table 1. Medium-sized loricariids with largest specimen 150.5 mm SL. Body stout. Head sloped from snout at approximate 40° angle to point above anterior portion of eye. Dorsal profile from point above anterior portion of eye ascending slightly to anterior insertion of dorsal fin. Dorsal profile from anterior insertion of dorsal fin decreasing to insertion of dorsal procurrent caudal rays then ascending to caudal fin. Body depth greatest below origin of dorsal fin. Ventral profile straight to caudal fin. Caudal peduncle triangular in cross section with dorsal surface flattened. Body widest at origin of pectoral fins, narrowest at base of caudal fin. Snout rounded when viewed from above.

Eyes moderately sized. Iris with dorsal flap. Interorbital space flat. Slight ridge present between anterodorsal margin of orbit and nares. Supraoccipital pointed posteriorly, slightly or not elevated above nuchal plate. Infraorbitals, frontal, nasal, pterotic, and supraoccipital supporting odontodes. Preopercle and opercle without odontodes.

Lips covered with short, wide papillae. Lower lip wide, upper lip narrow. Maxillary barbel only barbel present, reaching posteriorly more than one-third of distance to gill opening.

Median plates 24–26 (mode = 25). Plates unkeeled. Five caudal peduncle plate rows. Plates on all surfaces of body except for anteroventral margin of snout and most of ventral surface. Some small embedded plates present ventral to pectoral-fin girdle. Evertible cheek plates supporting hypertrophied odontodes that can be everted perpendicular to head. Cheek odontodes 35–73 (median = 53, mode unavailable no counts occurred more than once), longest evertible cheek odontode reaching to cleithrum. Hypertrophied cheek odontodes relatively weak. Slightly longer odontodes present along dorsal-, adipose-, pelvic-, caudal-, and pectoral-fin spines.

Dorsal fin II,7; dorsal spinelet V-shaped, dorsal-fin locking mechanism present, last ray of dorsal fin reaching insertion of adipose spine when adpressed, membranous connection present between last dorsal ray and body to preadipose plate. Adipose fin with single preadipose plate and moderately long spine. Caudal fin i,14.i; caudal fin forked, ventral lobe longer than dorsal lobe, dorsal procurrent caudal rays four, ventral procurrent caudal rays 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; pelvic-fin spine extending beyond base of anal fin when adpressed. Anal fin i,4; anal-fin spine slightly shorter than first ray.

Teeth bicuspid with lateral lobe three-quarters length of medial lobe and distal tip of lateral cusp one-half width of tip of medial cusp. Worn teeth with lobes approaching equal lengths. Left dentary teeth 34–51 (mode = 46). Left premaxillary teeth 37–54 (mode = 43).

Color in life. Adults with yellow-olive ground color on body and fins. Head, anterior sides to base of last dorsal-fin ray, and skin covering dorsal-fin base with distinct round white to cream-colored spots. Spots largest and more remotely spaced on anterior body, becoming gradually smaller and more closely spaced towards and onto snout. Fins usually uniformly yellow-olive. Dorsal fin occasionally with faint light spots on basal portions of membranes and sometimes rays. Juveniles often with orange-olive ground color, golden spots, and distal margins of dorsal and caudal fins bright orange.

Color in alcohol. Adults with head, sides, and fins nearly uniform gray-brown; plated ventral surfaces tan and naked abdominal region white to cream-colored (without markings). Faint round spots slightly lighter than ground color usually evident on posterior portion of head (between, below, and posterior to eyes) and anterior sides to insertion of last dorsal-fin ray. Light spots larger on sides and more remotely spaced; one to three spots per lateral plate anterior to dorsal fin and usually one spot per plate below dorsal-fin base (excepting large plates in ventral plate row). Light spots on posterior head smaller, more closely spaced, and often scarcely evident. Fin rays and membranes darkly pigmented with melanophores. Dorsal fin usually with faint roundish light spots largely restricted to basal half of membranes and sometimes fin rays. Pectoral and pelvic fins sometimes with faint roundish light spots largely restricted to basal portion of fins. Juvenile coloration similar to adults except light spots more obvious on anterior sides and head (but usually lacking from fins).

Range. Baryancistrus demantoides is known from the río Orinoco at its confluence with the río Ventuari and the lower río Ventuari upstream into the río Guapuchi ( Fig. 3 ).

Etymology. The specific name refers to a demantoid, a type of garnet that ranges in color from yellowish green to brownish green and it is in reference to the color of the fish. The word comes from the obsolete German word diemant meaning diamond and the Greek suffix -oïdes meaning to resemble.

Gut morphology and ecology. Gastrointestinal tract brown with yellow-green fat deposits, loosely attached to intestinal wall. Esophagus turns 90° toward right upon entering peritoneal cavity, extends straight to right for short distance, turns 90° toward posterior before transitioning into proximal (cardiac) stomach. Cardiac stomach extends posteriorly for two thirds of length then transitions into distal (pyloric) stomach by making a 180° turn such that pyloric portion exits anteriorly and lies to right of cardiac portion. Proximal intestines exit the anterior-facing pyloric stomach, turn 180° to cross dorsally over esophagus, then continuing posteriorly towards anus. Near the anus, the proximal and distal ends of intestines begin a parallel, clockwise spiral to the left with coils accruing ventral to stomach and esophagus. Proximal intestines spiral clockwise for half of entire intestinal length, turn 180° at their middle, then distal portion spirals back toward anus. Length of intestines and stomach from 15–21 times SL. External diameter of intestines ranges from 1–2 mm.

Baryancistrus demantoides was found exclusively among granite rocks in flowing water. Gut contents of two individuals consisted of a mixed brown organic and mineral matrix in which the only identifiable constituents were small tufts of filamentous algae attached to tiny grains of granite. Like most other ancistrins in the region, it likely feeds by scraping periphyton and indiscriminately ingesting both the sediment matrix deposited from the water column and the attached algae and benthic macroinvertebrates that often live within the sediment layers.

Figures

Fig. 1. Live specimens of a: Baryancistrus demantoides, adult,AUM 42034, paratype, 96.3 mm SL; b: B. demantoides, juvenile, MCNG 54031, paratype, 54.1 mm SL; c: Hemiancistrus subviridis,AUM 42933, 146.9 mm SL. Photos by M.H. Sabaj.

Fig. 2. Baryancistrus demantoides MCNG 54029, 150.5 mm SL; holotype, dorsal, lateral, and ventral views. Photos by D.C. Werneke.

Fig. 3. Localities of Baryancistrus demantoides (triangle), Hemiancistrus subviridis (dots), and both species (squares). 1 is the type locality of B. demantoides and 2 is the type locality of H. subviridis.