Pseudolithoxus dumus (Armbruster and Provenzano 2000)

Pseudolithoxus dumus, photo by M.H. Sabaj

Pseudolithoxus dumus is diagnosed from other Pseudolithoxus by the presence of a light body color with large, black spots at least anteriorly (spots may combine posteriorly to form bars). P. dumus can also be separated from all but P. tigris by the presence of light orange to cream-colored spots at the tip of the dorsal- and caudal-fin spines.

Body very dorsoventrally flattened with both ventral and dorsal surface flat.  Extremely hypertrophied odontodes present anterodistally on pectoral-fin spine.  Dorsal-fin spine weak; dorsal-fin spinelet supporting odontodes, v-shaped.  Dorsal fin short, folded dorsal fin not reaching median, unpaired preadipose plate.  Caudal fin weakly forked, lower lobe longer than upper.  Eyes mostly dorsal.  3 rows of plates on caudal peduncle.

Pterotic-supracleithrum bordered posteriorly at lateral line by small naked area ventrally and small plate dorsally.  Abdomen without plates.  Cheek odontodes hypertrophied, numerous, and set on evertible plates; odontodes fold into groove underneath opercle when relaxed.  Edge of snout anterior to evertible cheek plates with numerous hypertrophied odontodes.  All odontodes on opercle moderately elongated and stout.  Cheek plates and opercle never with thin, whiskerlike odontodes.  Pectoral-fin spine moderately elongated, reaching anus.

Dorsal II 7; pectoral fin I 6; pelvic fin I 5; anal fin I 5 (anal-fin spine about half first branched ray).  Teeth long and slender with large lateral and small mesial cusp; teeth 37-79 (58-67) per jaw ramus; tooth number tends to increase with standard length.  Lateral line plates 24-25 (25); dorsal plates 6-9 (7); interdorsal plates 6-7 (6); adipose-caudal plates 6-7 (6); folded dorsal-fin plates 11-14 (12); and postanal plates 11-13 (12).

Color in alcohol consists of gray-brown base color and fairly large, black spots on head and body to below middle of dorsal fin.  Spots fade towards caudal fin, spots either absent on caudal peduncle, present only along midline, or combine to form thin, often wavy black bars (see Comments.  Four faint saddles occasionally visible on back, first below anterior of dorsal fin, second below posterior of dorsal fin, third between dorsal and adipose fins, and fourth under adipose-fin membrane.  Fin rays and spines spotted so that fins appear banded (caudal fin occasionally entirely gray).  Dorsal- and caudal-fin spines tipped with light orange or cream-color spots.  Adipose-fin membrane dark.  Abdomen just slightly lighter than side.

Known from the upper Río Orinoco and tributaries of southern Venezuela from about Puerto Ayacucho to the Río Casiquiare.

From the Latin dumus for thorn-bush, in reference to the well developed odontodes on the pectoral-fin spines and snout; treated as a noun in apposition.

Holotype.  MBUCV V-17544, 86.8 mm SL, Venezuela, Estado Amazonas; Río Orinoco, backwater behind sand playa circa 0.5 hr upstream from Isla Temblador, 03°04íN 66°28íW, B. Chernoff, H. Lopez, W. G. Saul, J. Fernandez, O. Castillo, M. E. Antonio, J. Moreno, 10 March 1987.

Paratypes.  All collections Venezuela, Estado Amazonas.  ANSP 162403, 1, 70.6 mm SL; MBUCV V-17543, 1, 79.9 mm SL, collected with holotype. - MCNG 25796, 1, 58.4 mm SL, Departmento Atabapo, Río Ocamo at Raudal Arata, 03°08íN 64°34íW, L. Nico and J. Castillo, 24 January 1990. - ANSP-162160, 1, 99.1 mm SL, Río Orinoco, creek between the island and the beach, just downstream from Quiritare, (Quiritare is at 03°02íN 66°04íW), B. Chernoff, H. Lopez, J. Fernandez, and W. G. Saul, 11 March 1987.

Non-types.  All collections Estado Amazonas, Venezuela.  FMNH 106027, 2, 81.9 - 83.5 mm SL; MBUCV V-23082, 1, 41.9 mm SL, Río Ventuari, S side of river ca 0.5 hr. (ca. 12 km) above mouth in Río Orinoco, Laguna Pavón, 04°04íN 66°56íW, B. Chernoff, A. & D. Machado, and J. Wheeler, 24 January 1991. - ANSP 160769, 1, 101.2 mm SL; MBUCV V-16867,1, 76.1 mm SL, Morichal, 26 km from Puerto Ayacucho on road to Caicara, B. Chernoff, B. Saul, and R. Royero, 15 November 1985. - MBUCV V-14649, 1, 89.6 mm SL, Río Cataniapo, Raudal Yawi 5 river km upstream from La Reforma, 28 December 1984.

LITERATURE CITED

Armbruster, J.W. and F. Provenzano. 2000.  Four new species of the suckermouth armored catfish genus Lasiancistrus (Loricariidae: Ancistrinae). Ichthyological Exploration of Freshwaters 11:241-254.

Armbruster, J. W. 1997. Phylogenetic relationships of the sucker-mouth armored catfishes (Loricariidae) with particular emphasis on the Ancistrinae, Hypostominae, and Neoplecostominae. Unpubl. Ph.D. dissertation, Univ. Illinois, Urbana-Champaign, 409 pp.

Armbruster, J. W. 1998. Phylogenetic relationships of the suckermouth armored catfishes of the Rhinelepis group (Loricariidae: Hypostominae). Copeia 1998: 620-636.

Armbruster, J. W. & M. Hardman. 1999. Redescription of Pseudorinelepis genibarbis (Loricariidae: Hypostominae) with comments on behavior as it relates to air-holding. Ichthyol. Explor. Freshwaters, 10: 53-61.

Armbruster, J. W. & L. M. Page., 1996. Redescription of Aphanotorulus (Teleostei: Loricariidae) with description of one new species, A. ammophilus, from the Río Orinoco basin. Copeia, 1996: 379-389.

Boeseman, M. 1968. The genus Hypostomus Lacépède, 1803, and its Surinam representatives (Siluriformes, Loricariidae). Zool. Verhand., 99: 1-89.

Heitmans, W. R. B., H. Nijssen, & I. J. H. Isbrücker. 1983. The mailed catfish genus Lasiancistrus Regan, 1904, from French Guiana and Surinam, with descriptions of two new species (Pisces, Siluriformes, Loricariidae). Bij. Dierk., 53: 33-48.

Isbrücker, I. J. H. 1980. Classification and catalogue of the mailed Loricariidae (Pisces, Siluriformes). Versl. Techn. Gegevens, Univ. van Amsterdam, 22: 1-181 pp.

Leviton, A. E., R. H. Gibbs, E. Heal, & C. E. Dawson. 1985. Standards in herpetology and ichthyology: Part I. Standard symbolic codes for institutional resource collections in herpetology and ichthyology. Copeia, 1985: 802-832.

Sabaj, M.H., J.W. Armbruster, and L.M. Page. In Press. Spawning in Ancistrus with comments on the evolution of snout tentacles as a novel reproductive strategy: larval mimicry. Ichthyol. Explor. Freshwaters.

Taylor, W. R. & G. C. Van Dyke. 1985. Revised procedures for staining and clearing small fishes and other vertebrates for bone and cartilage study. Cybium 9: 107-119.

Weidner, T. 1996. Loricariiden aus Venezuela. DATZ 1996: 756.