Delturus carinotus, 1889

Reis, Roberto E., Pereira, Edson H. L. & Armbruster, Jonathan W., 2006, Delturinae, a new loricariid catfish subfamily (Teleostei, Siluriformes), with revisions of Delturus and Hemipsilichthys, Zoological Journal of the Linnean Society 147 (2), pp. 277-299 : 293-295

DELTURUS CARINOTUS LA MONTE ( FIG. 11 )

Plecostomus (Carinotus) carinotus La Monte, 1933: 2 , fig. 1 (type locality: Rio Doce , Estado do Espírito Santo, eastern Brazil).

Specimens examined: Brazil: Holotype (photographs examined): AMNH 11911 (235.0 mm SL), Rio Doce , Espírito Santo, 1932 . Other specimens: Minas Gerais: MZUSP 66189 (1, 182.8 mm SL), Rio Suaçuí Grande at São Pedro do Suaçuí (18°22′S 42°31′W), 25 November 2000 . MZUSP 66188 (2, 138.9– 206.4 mm SL), Rio Suaçuí Grande at São Pedro do Suaçuí (18°22′S 42°34′W), 26 November 2000 . MCP 28039 (2, 184.3– 204.2 mm SL), Rio Doce, Resplendor , April 1997 . MZUSP 52566 (1, 208.8 mm SL) Rio Santo Antônio at confluence with Ribeirão Pitangas, Braúnas , 11 August 1997 . MZUSP 42037 (1, 149.7 mm SL), Rio Casca downstream of Cachoeira do Inferno , 7 March 1990 . MZUSP 42139 (1, 140.1 mm SL), Rio Munhaçu at Caratinga , no date . MCP 28037 (13 + 1 c&s, 114.5– 207.7 mm SL), Rio Santo Antônio at the limit between Joanésia and Braúnas , 12 April 2000 . MCP 28038 (1, 278.7 mm SL), Rio Santo Antônio at the limit between Joanésia and Braúnas , October 2000 .

Diagnosis: Delturus carinotus is distinguished from all other Delturus by its narrower cleithral width (29.8–33.2% SL vs. 32.2–35.2% SL), and by its very small, indistinct dorsal flap on the iris (vs. flap large); from D. angulicauda by having a spotted caudal fin (vs. caudal fin light unspotted); from D. parahybae by the premaxillary tooth count (40–85 vs. 15–24) and by having eight to ten (usually nine) plates between the end of the anal-fin base and the caudal fin [vs. ten to 11 (usually ten)]; from D. brevis it is further distinguished by its concave caudal fin (vs. convex), and straight dorsal-fin margin (vs. rounded).

Description: SL of examined specimens 138.9– 208.8 mm. Other morphometric data are presented in Table 2 .

Body depressed and progressively narrowing from cleithrum to end of caudal peduncle. Dorsal profile of body smoothly convex. Body arches from snout tip to end of supraoccipital process; slightly convex to straight from posterior tip of supraoccipital to origin of dorsal fin. Dorsal profile descends from origin of dorsal fin to end of caudal peduncle. Trunk mostly round in cross-section, caudal peduncle flattened ventrally and more compressed caudally; trunk somewhat triangular at preadipose region. Greatest body depth at dorsal-fin origin. Dorsal surface of body mostly covered by dermal plates. Three to five median, preadipose plates present, forming tall ridge between dorsal and adipose fins. Lower surface of head and abdomen naked, except for some platelets sometimes embedded in skin laterally below the pectoral girdle. Median series of lateral plates with 22–25 plates; eight to ten plates bordering dorsal-fin base; eight to ten plates between end of anal-fin base and caudal fin.

Head broad and depressed. Snout convex anteriorly. Three slightly elevated ridges between orbits and snout tip, lateral ridges more prominent. Dorsal region of head between orbits flat to slightly concave; upper margin of orbits slightly higher than interorbital space. Eye large (orbit diameter 19.0–22.0% HL), placed dorsolaterally. Iris with very small, indistinct dorsal flap. Lateral margins of head with many thin hypertrophied odontodes in mature males. Lips well developed, occupying most of ventral surface of head. Upper lip with several transversely elongate papillae. Lower lip wide, reaching anterior margin of cleithrum. Lower lip mostly covered with minute papillae, smaller posteriorly. Maxillary barbel short, free. Teeth slender, bifid, two cusps approximately equal in size ( Fig. 2 ). Premaxilla with 40–85 teeth; dentary with 38–80 teeth. Distinct skin fold present anterior to premaxillary teeth and posterior to dentary teeth.

Dorsal fin originating slightly anteriorly to vertical line passing through pelvic-fin origin; dorsal-fin spinelet V-shaped and locking mechanism functional; one unbranched and nine to ten (usually nine) branched rays; its margin approximately straight. Fin membrane uniting last dorsal-fin ray to first preadipose plate or terminating just anterior to first preadipose plate. Pectoral fins moderate in size, with one slightly curved and flattened unbranched ray, and six branched ones. First thickened pectoral-fin ray of mature males covered with large hypertrophied odontodes on anterodorsal margin. Posterior pectoral-fin margin straight to slightly round, reaching proximal third of pelvic fins when adpressed. Pelvic fins moderate in size, with one unbranched and five branched rays, not or just reaching origin of anal fin when adpressed. Anal fin with one unbranched and five branched rays. Caudal fin slightly concave; lowermost ray slightly longer than uppermost, 14 branched rays; three to four upper and three to four lower procurrent caudal-fin rays.

Colour in alcohol: Ground colour of dorsal surface of head and body light brown; pale yellow ventrally. Dorsum and flanks covered with vermiculate dark brown markings, mostly arranged on borders of plates and skin between plates. Dorsal, pectoral, pelvic, and caudal fins with dark bands, sometimes disconnected and forming large blotches. Anal fin with few dark spots or indistinct bands. Ventral surface of head and body mostly unpigmented, except for light brown, scattered melanophores on caudal peduncle and upper lip.

Distribution: Delturus carinotus is known from a few localities in the upper portions of the Rio Doce basin, in the State of Minas Gerais, Brazil ( Fig. 5 ).

Ecology: Specimens collected recently were found in wide sectors of the river channels, with strong currents and a rocky bottom.

Figures

Figure 2. Teeth of the Delturinae. A, right premaxilary tooth of Delturus angulicauda, USNM 318180, lateral view. Scale bar 1 mm. B–H, dorsal view of right premaxillary tooth crown. B, D. parahybae, MCZ 7726. C, D. angulicauda, USNM 318180. D, D. carinotus, MCP 28039. E, D. brevis, MZUSP 69858. F, Hemipsilichthys papillatus, MCP 21423. G, H. nimius, MCP 31990. H, H. gobio, MCP 19780. Scale bar 250 µm.

Figure 5. Geographical distribution of the species of Delturus and Hemipsilichthys in south-eastern Brazil.

Figure 11. Delturus carinotus, MCP 28038, 278.0 mm standard length, male, Rio Santo Antônio at Braúnas, Minas Gerais.