Hypostomus weberi, Carvalho & Lima & Zawadzki, 2010

Carvalho, Pedro Hollanda, Lima, Flávio C. T. & Zawadzki, Cláudio H., 2010, Two new species of the Hypostomus cochliodon group (Siluriformes: Loricariidae) from the rio Negro basin in Brazil, Neotropical Ichthyology 8 (1), pp. 39-48 : 44-46

Hypostomus weberi , new species

Fig. 3

Cochliodon sp.: Goulding et al., 1988: 128, 141 (rio Negro basin, Brazil; diet, habitat).

Holotype: MZUSP 98767, 149.3 mm SL, Brazil, Amazonas , Barcelos, rio Negro, 0°58’S 62°57’W, 2 Feb 1980, M. Goulding.

Paratypes: All from Brazil, State of Amazonas , rio Negro basin: MZUSP 34598 , 2 , 141.8 - 162.8 mm SL, same data as holotype. MZUSP 34604 , 5 , 107.0- 174.5 mm SL, NUP 6344 , 1, 156.6 mm SL, rio Marauiá , near the mouth, “igapó” (= flooded forest), 0 o 24’S 65 o 12’W, 27 May 1979, M. Goulding. MZUSP 34765 , 1, 152.1 mm SL, rio Negro, below rio Daraá, “pedral” (= rapids), 0 o 28’S 64 o 46’W, 16 Feb 1980, M. Goulding .

Additional material (non-types): MNRJ 1066, 1, 151.3 mm SL, “rio Cicipa, limite Brasil-Venezuela” [sic]; March 1933, C. Lako.

NRM 17079, 1, 158.1 mm SL, “ Brazil or Peru, rio Amazonas or rio Negro drainages”, 1923-1925, D. Melin et al.

Diagnosis. Hypostomus weberi is distinguished from all Hypostomus species , except those belonging to the Hypostomus cochliodon group, by having few teeth bearing a small outer cusp (10 to 13) and acutely angled dentaries. It is distinguished from the remaining members of the Hypostomus cochliodon group, except H. hemicochliodon , H. kopeyaka , H. sculpodon , and H. soniae , by possessing bicuspid teeth with mesial cusp rounded, considerably larger than outer cusp (vs. teeth generally unicuspid, outer cusp, if present, almost imperceptible, mesial cusp large and distinctly spoon-shaped). Hypostomus weberi can be distinguished from H. hemicochliodon , H. kopeyaka , H. sculpodon , H. soniae , and H. weberi by its unique color pattern, with large, black, rounded spots widely-spaced and sharply defined, on the head, dorsal surface and fins (vs. spots absent in H. soniae , spots present in the remaining species, elongated and closelyset in H. kopeyaka , and small and rounded in H. hemicochliodon and H. sculpodon ). Additionally, it is distinguished from all the members of the Hypostomus cochliodon group, except H. kopeyaka , H. ericae , H. hemicochliodon , H. paucipunctatus , H. sculpodon and H. waiampi , by having a buccal papilla. See the Discussion, for additional remarks on the diagnosis of Hypostomus weberi .

Description. Meristic and morphometric data in Table 1. Overall view of body in Fig. 3 . Dorsal profile slightly convex to straight from snout tip to interorbital area, highly convex from interorbital area to dorsal-fin origin, and almost straight from dorsal-fin origin to end of adipose fin. Ventral profile almost straight from snout tip to caudal fin. Caudal peduncle laterally compressed, roughly ovoid in cross section. Body width at cleithral region greater than head depth. Head broad and deep, covered dorsally with plates, except for small naked area on snout tip. Median elongate bulge associated with mesethmoid, terminating coequally with transversal through nares. Supraoccipital bone with conspicuous highly developed median ridge, and with well-developed posterior process bordered by wide nuchal plate. Conspicuous ridge originating laterally to the nares, passing through supraorbital, and extending to posterior portion of pterotic-supracleithrum. Opercle medium to large, with odontodes more developed distally. Oral disk round, medium-sized, lower lip not reaching transversal through gill openings, ventral surface covered with numerous small papillae decreasing in size posteriorly. Maxillary barbels moderately developed, about the same size as orbital diameter.Anterior surface of upper lip covered with odontodes, continuous with patch of odontodes on snout. Buccal papilla medium to large-sized. Jaws acutely angled, averaging less than 80 o between left and right dentaries rami. Ten to 12 (mode 12, holotype 11) teeth in premaxilla, ten to 13 (mode 11, holotype 13) in dentary. Teeth bicuspid, curved inward distally, mesial cusp considerably larger than lateral cusp, rounded in shape (similar to the condition found in Hypostomus soniae, Hollanda-Carvalho & Weber, 2004 : fig. 4d, and H. hemicochliodon, Armbruster, 2003 : fig. 1B).

Body covered with five rows of moderately spinulose dermal plates. Small naked area on snout tip, about the size of the nares. Dorsal-fin base naked. Predorsal region with two conspicuous keels, area between keels flat. Dorsal series of lateral plates with keel from first to third plate, displaced downward from fourth plate onwards, and extending to sixteenth to seventeenth dorsal plate. Mid-dorsal series of lateral plates with keel from first to third plate, slightly displaced downward from fourth plate onwards, and extending to 26 th to 27 th mid-dorsal plate. Median series of plates with moderately-developed keel and bearing lateral line. Midventral series of plates with keel more developed from the first to the fifth or sixth plate. Ventral surface of head covered with minute platelets, with exception to the region beneath lower lip. Abdomen completely covered with minute platelets in specimens larger than 135 mm SL, with exception of small areas around pectoral- and pelvic-fin insertions and at urogenital opening. Preanal plate present, wide. Twenty-three dorsal plates, 26 to 28 (mode 27) mid-dorsal plates, 26 to 28 (mode 27) median plates, 27 to 28 (mode 28) mid-ventral plates, 22 to 23 (mode 23) ventral plates. Three predorsal plates, eight plates below dorsal fin, seven plates between dorsal fin and adipose fin, eight plates between adipose fin and caudal fin, 13 to 14 plates between anal fin and caudal fin (mode 14).

Dorsal-fin II,7, its origin situated approximately at midpoint between pectoral and pelvic fins, or slightly posterior to that point. Dorsal-fin margin convex.Adipose-fin spine compressed and curved inward, straight in smaller specimens. Pectoral fin i,6, its posterior border straight. Pectoral-fin spine slightly curved inward, covered with weakly developed odontodes, considerably more developed on its distal portion in larger specimens. Tip of adpressed pectoral fin reaching one-third pelvic-fin spine length. Pelvic-fin I,5, its posterior border straight to slightly rounded. Pelvic-fin spine just surpassing anal-fin origin when adpressed. Anal fin i,4, its tip reaching the fourth or fifth plate after its origin. First to third branched anal-fin rays similar in size, unbranched and fourth branched rays slightly smaller. Caudal-fin margin concave, i,14,i, with inferior lobe longer than superior one.

Color in alcohol. Overall ground color of body and fins chestnut-brown to dark-brown lighter on ventral surface. Dorsal surface of head and body entirely covered by rounded, large dark spots, more numerous, smaller and closely-set on head, larger and widely-set on trunk and ventral area. Caudal peduncle spots elongated in some specimens. Abdominal spots coalescing into larger spots in some specimens. Spots on fins usually uniformly distributed, except on caudal fin which is often devoid of spots on its base.

Distribution. Hypostomus weberi is known from the middle rio Negro area at Barcelos and its tributary, the rio Marauiá ( Fig. 4 ). There is a single poorly preserved specimen (MNRJ 1066), apparently belonging to this species, recorded from an uncertain locality, “rio Cicipa”, said to be at the Brazilian/ Venezuelan border. There is no “rio Cicipa” in the upper rio Negro area in Brazil, and this locality is certainly misspelled. It is possible that “rio Cicipa” correspond to río Siapa, a tributary of the río Casiquiare in Venezuela. That suggests that Hypostomus weberi is distributed farther upstream into the upper rio Negro, an assumption that need to be corroborated with further collecting in the area. The specimen NRM 17079, whose exact provenience is also uncertain, was very probably collected somewhere in the rio Negro basin in Brazil, an area visited by the collector of the species, the herpetologist Douglas Melin, between 1923 - 1924 (Melin, 1941). Specimens MNRJ 1066 and NRM 17079 were thus not included in the type series both because of their uncertain locality data and poor state of preservation.

Ecological notes. Goulding et al. (1988: 141) mentions detritus as the principal food item found in gut contents of four specimens of Hypostomus weberi (as Cochliodon sp.). Specimens of Hypostomus weberi were reported as being collected both at rapids (“pedral”) and flooded forest (“igapó ”).

Etymology. The name weberi , after Claude Weber, from the Muséum d’Histoire Naturelle de Génève, for his contributions to the knowledge of the genus Hypostomus .

Figures

Fig. 3. Hypostomus weberi, holotype, MZUSP 98767, 149.3 mm SL: dorsal, lateral, and ventral views.

Fig. 4. Map of northern SouthAmerica, showing distributions of Hypostomus kopeyaka (squares) and Hypostomus weberi (dots). Black symbols refer to type-localities.