Denticetopsis epa, Vari & Ferraris Jr & de Pinna, 2005

Vari, Richard P., Ferraris Jr, Carl J. & de Pinna, Mário C. C., 2005, The Neotropical whale catfishes (Siluriformes: Cetopsidae: Cetopsinae), a revisionary study, Neotropical Ichthyology 3 (2), pp. 127-238 : 206-208

Denticetopsis epa , new species

Figs. 45-46 , Tables 16-22

Diagnosis. Denticetopsis epa can be differentiated from D. royeroi and D. sauli by the combination of the lack of elongate, symphyseal teeth on the dentary, the lateral line extending posteriorly on the body beyond the abdomen at least onto the caudal peduncle, the presence of dentition on the vomer, a dorsal fin with 5 or 6 segmented rays and a first ray that is spinous basally, a symmetrical, shallowlyforked caudal fin, and the possession of horizontally-elongate, stellate, dark chromatophores on the body when the chromatophores are expanded. Denticetopsis epa differs from D. macilenta in the relative length of the pelvic fin (tip of the pelvic fin reaching to the posterior margin of the vent versus falling just short of the anterior margin of the vent, respectively), in the relative position of the eye (anterior limit of eye located at, or posterior of, the vertical through the anterior limit of the maxillary-barbel groove versus middle of the eye located at the vertical through the anterior limit of the maxillary-barbel groove, respectively). Denticetopsis epa differs from D. praecox in the relative length of the pelvic fin (reaching to the posterior margin of the vent versus falling just short of the anterior margin of the vent, respectively) and in the number of premaxillary tooth rows (three rows of teeth on premaxilla in all but smallest examined specimens versus two rows of teeth, respectively). Denticetopsis epa differs from D. iwokrama in the number of total anal-fin rays (25 to 27 versus 29, respectively) and in the number of caudal (26 to 28 versus 32, respectively), preanal (14 or 15 versus 17, respectively), and total vertebrae (38 to 40 versus 43, respectively). Denticetopsis epa differs from D. seducta in the relative position of the origin of the anal fin (approximately at the vertical through the middle of TL versus distinctly anterior of that point, respectively) and in the relative depth of the caudal peduncle relative to the length of the caudal peduncle (depth/length 1.15-1.3 versus 1.33-1.5, respectively).

Description. Body moderately-elongate, slightly-compressed laterally anteriorly and becoming progressively distinctlycompressed posteriorly. Body depth at dorsal-fin origin approximately 0.25 of SL, and approximately equal to distance from anterior margin of eye to posterior margin of opercle. Lateral line on body complete, unbranched, and midlateral; extending from vertical through pectoral-fin base onto caudal peduncle but falling to varying degrees short of posterior margin of hypural plate. Dorsal profile of body nearly straight from nape to dorsal-fin origin and nearly straight from dorsalfin origin to caudal-fin base. Ventral profile of body convex along abdomen, approximately straight, but posterodorsallyslanted, along base of anal fin. Caudal-peduncle depth approximately 1.5 times caudal-peduncle length.

Head in profile acutely triangular overall with bluntlypointed snout. Dorsal profile of head slightly convex from tip of snout to nape. Ventral profile of head slightly convex. Margin of snout in dorsal view ranging from rounded to bluntly triangular. Postorbital margins of head running nearly in parallel from dorsal view. Enlarged jaw musculature very evident externally on dorsal surface of postorbital portion of head.

Opercular membrane attaching to isthmus only anterior of vertical through pectoral-fin insertion. Opercular opening moderate; extending ventral of pectoral-fin insertion by distance equal to distance from tip of snout to posterior margin of eye and extending dorsal of pectoral-fin insertion by distance equal to diameter of eye.

Eye situated on lateral surface of head; located entirely dorsal to horizontal extending through pectoral-fin insertion; eye visible in dorsal view, but not in ventral view, of head. Middle of orbit at approximately anterior one-third of HL. Eye diameter approximately one-third of snout length. Interorbital width slightly greater than distance from tip of snout to posterior margin of orbit.Anterior narial opening circular, surrounded by short, anteriorly-directed, tubular rim of skin. Opening of anterior nares located along horizontal extending through maxillary-barbel origin and ventral of horizontal extending through tip of snout. Distance between anterior nares approximately equal to distance from tip of snout to middle of eye. Posterior narial opening located on dorsal surface of head, situated along vertical through anterior margin of orbit; narial opening rounded and completely surrounded by flap of skin of nearly uniform height and with posterior margins of flap in contact.

Mouth inferior; its width approximately one-half of HL. Margin of lower jaw gently rounded, its posterior limit reaching to vertical through posterior margin of orbit. Premaxillary tooth patch in form of gently-arched band, continuous across midline, with anterior margin convex and posterior margin concave and running in parallel to anterior margin. Teeth on premaxilla small, conical, and sharply-pointed, with teeth arranged in two regular rows of uniform-sized teeth, and with variable number of teeth situated anterior of those two series that sometimes form irregular, third row. Vomerine teeth arranged in single, arched row with small gap in series at midline. Vomerine teeth stout and conical, becoming progressively larger laterally, with even smallest teeth on vomer larger than teeth on premaxilla. Dentary teeth comparable in shape to, but larger in size than, premaxillary teeth. Dentary dentition consisting of three, irregular row medially that taper to one row laterally.

Maxillary barbel slender, its length approximately equal to distance from tip of snout to rear of eye, and approximately one-third of HL; barbel origin located ventral to middle of orbit. Medial mental barbel slightly shorter than lateral mental barbel, with latter approximately equal in length to maxillary barbel. Medial mental-barbel origin located along vertical through rictus. Lateral mental-barbel origin situated slightly posterior of vertical through medial mental-barbel origin. Tips of adpressed mental barbel falling short of posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.29-0.31 of HL. Length of longest branched dorsal-fin ray equal to approximately one-half of HL. Dorsal-fin spinelet absent. First dorsal-fin ray spinous for basal one-half of length but flexible more distally; without distal filament present in some species of the Cetopsinae . Distal margin of dorsal fin convex, with second branched ray longest. Dorsal-fin origin located at approximately anterior 0.25-0.27 of SL and situated along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin reaching vertical through vent. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal fin shallowly-forked, symmetrical; tips of lobes rounded. Length of longest caudal-fin ray approximately 1.5 times length of middle fin rays.

Base of anal fin moderately long. Anal-fin origin located distinctly posterior of middle of SL and approximately at middle of TL. Anal-fin margin slightly convex in all examined specimens. Membranous attachment present between posterior margin of basal one-half of posterior most anal-fin ray and caudal peduncle.

Pelvic fin moderately long; distal margin slightly convex, with middle fin rays longest. Pelvic-fin insertion located anterior to middle of SL and along vertical through posterior terminus of base of dorsal-fin. Tip of adpressed pelvic fin extending past middle of SL, and reaching posterior margin of vent. Medial most pelvic-fin ray with membranous attachment to body along basal one-fourth of its length.

Pectoral-fin length approximately one-half of HL. Pectoral-fin margin distinctly convex, with middle ray longest. First pectoral-fin ray spinous with smooth margins and proportionally short, with length approximately one-half that of first branched fin ray.

Distribution. Denticetopsis epa is known from several localities in the lower portions of the rio Tocantins basin ( Fig. 46 ).

Etymology. The species name, epa , is in reference to the Brazilian Expedição Permanente de Amazônia, commonly cited as EPA, which collected large series of scientifically valuable fishes across broad expanses of the Amazon basin and that collected the type series of Denticetopsis epa . It is treated as a noun in apposition.

Material examined. 20 specimens (20, 18-47 mm SL). Holotype. Brazil. Pará: Igarapé do Limão, rio Tocantins, Baião (2°41’S, 49°41’W), Expedição Permanente de Amazônia ( EPA), 9 September 1970, MZUSP 24060 , 1 (47) . Paratypes. 19 specimens (19, 18-44 mm SL). Brazil. Pará: Igarapé do Limão, rio Tocantins, Baião (2°41’S, 49°41’W), Expedição Permanente de Amazônia ( EPA), 9 September 1970, MZUSP 83228 , 7 (27-44, 4 specimens, 27-44 mm, cleared and stained) ; USNM 372767 , 2 (30-37) . Igarapé # 5, km 5 on road from Tucuruí to Mato Grosso, Expedição Permanente de Amazônia ( EPA), MZUSP 24183 , 7 (18-31; 2 specimens, 34-35 mm, cleared and stained) . Igarapé Pacuí , at km 97 on highway between Belém and Brasília (1°36’S, 47°13’W), MZUSP 22279 , 3 (30-37.5).

Coloration in alcohol. Available specimens apparently largely depigmented. Body in most intensely pigmented specimens with lateral and dorsal surfaces covered with diffuse, horizontally-elongate, dark spots when chromatophores expanded; horizontally-elongate chromatophores supplemented by some scattered, smaller, more-darkly pigmented spots. Less darkly-pigmented specimens with widely-scattered, small, dark spots on body; spots occasionally very few in number. Head with diffuse, dark pigmentation scattered over dorsal and lateral surfaces. Less intensely-pigmented specimens with proportionally fewer chromatophores on head. Abdomen and ventral surface of head pale.

Dorsal fin dusky basally and pale distally. Anal, caudal, pelvic, and pectoral fins pale to very slightly dusky.

Barbels with scattered, dark pigmentation basally and pale distally.

Sexual dimorphism. The examined specimens of Denticetopsis epa lack the sexually-dimorphic features of the dorsal, pectoral, and anal fins that are characteristic of many species in the Cetopsinae , albeit not the other species of Denticetopsis .

Figures

Fig. 45. Denticetopsis epa, new species, holotype, MZUSP 24060, 47 mm SL; Brazil, Pará, Igarapé do Limão, rio Tocantins, Baião (2°41’S,49°41’W).

Fig. 46. Map of central and northern SouthAmerica showing geographic distribution of Denticetopsis epa (1 = holotype locality), Denticetopsis iwokrama (2 = holotype locality), Denticetopsis macilenta (3 = holotype locality of Hemicetopsis macilenta), Denticetopsis praecox (4 = holotype locality), Denticetopsis royeroi (5 = holotype locality), Denticetopsis sauli (6 = holotype locality), and Denticetopsis seducta (7 = holotype locality) (some symbols represent more that one locality and/or lot of specimens).