Hypostomus denticulatus, Zawadzki & Weber & Pavanelli, 2008

Zawadzki, Cláudio H., Weber, Claude & Pavanelli, Carla S., 2008, Two new species of Hypostomus Lacépède (Teleostei: Loricariidae) from the upper rio Paraná basin, Central Brazil, Neotropical Ichthyology 6 (3), pp. 403-412 : 404-408

Hypostomus denticulatus , new species

Fig. 1

Hypostomus sp. 7 .- Zawadzki, 2001: 21 [photo; rio Corumbá, affluent of rio Paranaíba; comparison to other species of Hypostomus ; allozymes].- Pavanelli et al., 2007: 61 [rio Corumbá basin, affluent of rio Paranaíba].

Holotype. MZUSP 98770, 161.9 mm SL, Brazil, Goiás state, Município de Caldas Novas, rio do Peixe, tributary to rio Corumbá , rio Paranaíba drainage, Pires do Rio , 17°34’24”S, 48°29’50”W, 21 Sep 1996, Nupélia.

Paratypes. All from Brazil, Goiás State, upper rio Paraná basin: ANSP 187499 , 1, 165.7 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Caldas Novas , Pires do Rio , 17°36’06”S, 48°28’01”W, 8 Oct 1999, Nupélia; MHNG 2709.052 , 1, 172.9 mm SL, rio Pirapitinga , tributary to rio Corumbá , Município de Caldas Novas , Pires do Rio , 17°43’37”S, 48°32’54”W, 6 Nov 1999, Nupélia; NUP 480, 3, 107.3- 147.1 mm SL, rio Corumbá (Corumbá Reservoir), tributary to rio Paranaíba , Município de Caldas Novas , Ipameri, 17°42’43”S, 48°29’52”W, 12 Nov 1996 to 11 May 1999, Nupélia; NUP 4233, 1, 165.8 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Caldas Novas , Pires do Rio , 17°34’24”S, 48°29’50”W, 5 Oct 1999, Nupélia; NUP 4306, 2, 144.3- 158.5 mm SL, rio Corumbá , tributary to rio Paranaíba , Município de Pires do Rio , Ipameri, 17°29’02”S, 48°22’13”W, 22 May 1996, Nupélia; NUP 4308, 2, 166.7- 186.4 mm SL, rio Corumbá (downstream the Corumbá Reservoir), tributary to rio Paranaíba , Município de Caldas Novas , Corumbaíba, 18°00’33”S, 48°32’19”W, 7 Feb 1999, Nupélia; NUP 5574, 2, 117.7- 136.9 mm SL, rio Corumbá (Corumbá Reservoir), tributary to rio Paranaíba , Município de Caldas Novas , Corumbaíba, 17°43’37”S, 48°32’54”W, 10 Nov 1996, Nupélia; NUP 5617, 2, 93.1-99.8 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Pires do Rio , Ipameri, 17°36’S, 48°24’”W, 28 Oct 1997, Nupélia; NUP 5619, 1, 134.5 mm SL, Corumbá Reservoir, rio Corumbá , tributary to rio Paranaíba , Município de Caldas Novas , Corumbaíba, 17°43’37”S, 48°32’54”W, 15 Dec 1996, Nupélia; NUP 5620, 2, 182.6- 191.3 mm SL, rio Corumbá (Corumbá Reservoir), tributary to rio Paranaíba , Município de Caldas Novas , Ipameri, 17°42’43”S, 48°29’52”W, Aug 1997, Nupélia; NUP 5635, 1, 156.6 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Pires do Rio , Ipameri, 17°36’06”S, 48°28’01”W, 20 May 1996, Nupélia; NUP 5637, 1, 120.1 mm SL, rio Corumbá , tributary to rio Paranaíba , Município de Pires do Rio , Ipameri, 17°29’02”S, 48°22’13”W, 6 Dec 1998, Nupélia. Non-measured paratypes: Goiás State: NUP 479, 6, 107.9- 132.4 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Pires do Rio , Ipameri, 17°36’S, 48°24’W, 12 Nov 1996, Nupélia; NUP 5571, 5, 90.0- 133.2 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Pires do Rio , Ipameri, 17°36’S, 48°24’W, 10 Nov 1996, Nupélia; NUP 5572, 1, 90.1 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Pires do Rio , Ipameri, 17°36’S, 48°24’W, 17 Oct 1996, Nupélia; NUP 5573, 1, 111.7 mm SL, rio do Peixe, tributary to rio Corumbá , Município de Pires do Rio , Ipameri, 17°36’S, 48°24’W, 30 Jun 2001, Nupélia; NUP 5621, 1, 109.1 mm SL, rio Corumbá (Corumbá Reservoir), tributary to rio Paranaíba , Município de Caldas Novas , Ipameri, 17°43’37”S, 48°32’54”W, 21 Oct 1996, Nupélia; NUP 5622, 2, 65.0- 145.9 mm SL, rio Corumbá (Corumbá Reservoir), tributary to rio Paranaíba , Município de Caldas Novas , Ipameri, 17°43’37”S, 48°32’54”W, 11 Dec 1996, Nupélia. Minas Gerais State: MZUSP 36788 , 2 , 136.3 - 154.4 mm SL, rio Paranaíba (São Simão Reservoir), tributary to upper rio Paraná, Município de Cachoeira Dourada , Oct 1985, A.C. Beaumord. Indefinite State: MNRJ 17624 , 1 , 147.0 mm SL, rio Preto , corredeira, right margin of rio Paranaíba , city and State not specified on label, 3 Aug 1997, O. Sagim Jr .

Diagnosis. Hypostomus denticulatus is distinguished from all congeners, except H. multidens and H. ternetzi , by having more than 115 teeth (vs. less than 109) per ramus on dentary and premaxilla. Hypostomus denticulatus is distinguished from similar-looking H. ternetzi by having 116-214 teeth per jaw ramus (mean 167, n = 20) vs. 39-127 teeth per ramus (mean 81.4, n = 20); beige to light-brown body color vs. dark brown; larger orbital diameter, 18.5 to 21.2% of HL (n = 20) vs. 14.5 to 16.1% (n = 20); abdomen naked vs. abdomen partially plated; and teeth with two symmetrical cusps ( Fig. 2a ) vs. two asymmetrical cusps ( Fig. 2b ). Hypostomus denticulatus is distinguished from H. multidens by having dark (vs. pale) spots over body and fins ( Fig. 3 ).

Description. Counts and measurements in Table 1. Body relatively short with rough plates. Cleithral width greater than head depth. Dorsal profile rising somewhat irregularly at an angle slightly less than 45 o from snout tip to dorsal-fin origin, and decreasing gently from that point to end of caudal peduncle. Head broad and moderately depressed, covered dorsally with dermal ossifications, except for small amorphous naked area on snout tip. Anterior profile of snout rounded in dorsal view. Median longitudinal bulge associated with mesethmoid usually conspicuous from snout tip to transverse line between nares. Eye large (18.5 to 21.2% of HL), dorsolaterally placed. Interorbital space moderately concave in frontal view. A pair of weak ridges on dorsal surface of head, each beginning lateral to naris, passing through upper margin of orbit and terminating on posterior portion of pteroticsupracleithrum. Supraoccipital with weak median ridge and slight, broadly triangular posterior process bordered by single predorsal plate, partially divided in some specimens. Predorsal region with weak medial keel; its uppermost portion flat.

Lips well developed and transversely ellipsoidal. Lower lip reaching or almost reaching transverse line between gill openings, its inner surface covered with numerous small papillae. Maxillary barbel short with free tip. Mouth large. Teeth long, very slender, bicuspid, and curved inward distally; mesial cusp similar in length and form to lateral cusp ( Fig. 2a ). Dentary teeth usually not overlapping medially. Dentary ramus flat, straight, and approximately forming a straight angle (usually ranging from 160° to 180°).

Five rows of slightly spinulose plates on side of body. Dorsal series of plates starting at vertical through dorsal-fin origin. A weak longitudinal keel begins on first plate of dorsal series and continues until dorsal procurrent caudal-fin plates. Mid-dorsal series of plates without keel or with a very weak keel. Median series bearing lateral line. Mid-ventral series forming longitudinal ridge along first five or six plates. Plates in ventral series right-angled transversely on caudal peduncle, forming a strong keel along lower portion of peduncle. Caudal peduncle roughly triangular in cross section.

Upper and lower lips without scutelets. Ventral surfaces of head and abdomen completely naked in specimens up to 131.2 mm SL; larger specimens with small platelets distributed just anterior to gill opening, in narrow transverse band between gill openings, laterally on abdomen between pectoral and pelvic fins (contacting ventral plates), and anterior to urogenital opening. Preanal plate partially exposed in specimens up to 129.8 mm SL, usually completely covered with skin in larger specimens.

Dorsal-fin origin situated two lateral-plate rows anterior to vertical through pelvic-fin origin. Dorsal fin large with flexible spine and seven branched rays; two posteriormost rays reaching or almost reaching adipose-fin origin. Adipose-fin spine straight and well developed. Pectoral fin with moderately inward-curved spine and six branched rays; distal margin straight. Pectoral-fin spine covered with poorly-developed odontodes; odontodes more developed distally in some larger specimens. Pectoral fin inserted on same horizontal plane as pelvic fin such that pectoral spine, when adpressed, lies on top of and reaches to approximately middle of pelvicfin spine. Pelvic fin with flexible and slightly inward-curved spine and five branched rays; distal border straight. Pelvicfin spine flattened ventrally; when adpressed spine tip reaches to about middle of anal-fin spine. Anal fin with flexible spine and four branched rays; spine tip reaching fifth plate posterior to its origin. Caudal fin slightly emarginate, with two longer outer spines and 14 inner branched rays; ventral lobe longer than dorsal lobe.

Color in alcohol. Background color of dorsal and lateral surfaces of head and body beige to light-brown. Head, dorsum, flanks and fins covered by many large dark spots. Dark spots generally merge into short and narrow vermiculations on anterior portion of head, becoming isolated and roundish on pterotic-supracleithrum and more elongate posteriorly. Spots most conspicuous on head and usually fade gradually on trunk towards caudal peduncle. Background color of ventral surfaces of head and body lighter than dorsal portions, except ventral portion of snout uniformly dark brown. Upper and lower lips and ventral surface of head without spots. Abdomen usually without spots or with very faded irregularly spaced dark spots in a few specimens. Ventral surface of caudal peduncle without spots.

Dorsal fin with roundish dark spots only on its base; spots merging distally into bands on interradial membranes paralleling rays. Adipose fin and caudal fin brown. Pectoral fin and pelvic fin with dark spots on spine, rays and interradial membranes. Anal fin with diffuse dark markings.

Distribution and habitat. Hypostomus denticulatus is known from the rio Corumbá in the vicinity of the Corumbá Reservoir, upper rio Paraná basin, Brazil ( Fig. 4 ). This species was mostly collected in the reservoir of the rio Corumbá just upstream from the dam, and its tributary the rio Areia. Water was turbid, substrates rocky with sand, and riparian vegetation variable and remnant. This species was not found associated with woody debris, and occurs syntopically with H. ancistroides , H. iheringii, H. margaritifer, H. regani, Hypostomus sp. , and the second new species described herein.

Etymology. From the Latin denticulus, meaning small teeth, plus - atus, meaning provided with.

Figures

Fig. 1. Hypostomus denticulatus, holotype, Brazil, Goiás state, Município de Caldas Novas, rio do Peixe, tributary to rio Corumbá, MZUSP 98770, 161.9 mm SL. Dorsal, lateral, and ventral views.

Fig. 2. Bicuspid premaxillary teeth of a, Hypostomus denticulatus with symmetrical cusps, and b, H. ternetzi with asymmetrical cusps. Ventral view.

Fig. 3. a, Hypostomus denticulatus, paratype, NUP 4308, 194.3 mm SL, and b, H. multidens, NUP 5340, 157.0 mm SL.

Fig. 4. Map of southeastern South America showing geographic distribution and type-locality (numbers) of Hypostomus heraldoi (dots; 1 = rio Pirapitinga), and H. denticulatus (squares; 2 = rio do Peixe).