Paracetopsis atahualpa, 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 : 223-224

Paracetopsis atahualpa , new species

Figs. 54-55 , Tables 23-29

Paracetopsis bleekeri [not of Bleeker, 1862].–Chang & Ortega, 1995: 4 [ Peru, Tumbes].

Diagnosis. Paracetopsis atahualpa is distinguished from all other species in the Cetopsinae with the exception of P. bleekeri and P. esmeraldas by the combination of the possession of a vomerine tooth patch with more than one row of teeth and a medial separation of the contralateral components of the patch. Paracetopsis atahualpa differs from P. bleekeri in the relative length of the pelvic fin (completely overlapping the vent versus falling short of the vent, respectively), the pigmentation pattern on the operculum (the possession of a distinct patch of dark pigmentation versus the lack of such pigmentation, respectively), in overall body pigmentation (dark versus light, respectively), in the extent of the medial gap in the vomerine tooth patch (with a limited medial gap between the contralateral components of the tooth patch equivalent to the width of one or two vomerine teeth versus with a distinct medial gap equivalent to the width of three of four vomerine teeth, respectively), and to a degree in the number of total vertebrae (50 versus 47 to 50 with 49 most common and 50 in only 1 of 21 radiographed specimens, respectively). Paracetopsis atahualpa differs from P. esmeraldas in the dorsal profile of the body at the area of contact of the posterodorsal portion of the externally apparent jaw musculature with the anterior portion of the epaxial musculature (with distinct notch versus smooth continuous profile, respectively), the degree of pigmentation of the basal portion of the maxillary barbel (distinctly dark versus pale or with few scattered, dark chromatophores, respectively), and to a degree in the number of caudal vertebrae (36 to 38 with 37 most common versus 37 to 40 with 38 most common, respectively; see Table 28) and number of total vertebrae (50 versus 50 to 53 with 51 most common, respectively; see Table 29).

Description. Body relatively elongate, slightly-compressed anteriorly and becoming distinctly-compressed posteriorly. Body depth at dorsal-fin origin approximately 0.26 of SL, and approximately equal to distance from anterior margin of orbit to posterior margin of opercle. Lateral line on body complete and midlateral; extending from vertical through pectoral-fin base to hypural plate with short, dorsal bend on hypural plate. Portion of lateral line on caudal peduncle with few short, ventrally-directed branches. Dorsal profile of body slightly convex from nape to dorsal-fin origin, straight from dorsal-fin origin to caudal-fin base. Distinct notch in body profile obvious in lateral view between posterodorsal margin of externally apparent jaw musculature and anterior margin of epaxial musculature. Ventral profile of body convex along abdomen, approximately straight, but posterodorsally-slanted along base of anal fin. Caudal-peduncle depth approximately equal to caudal-peduncle length.

Head in profile acutely triangular with bluntly-rounded snout. Dorsal profile of head nearly straight from tip of snout to nape. Ventral profile of head slightly convex. Profile of snout from dorsal view obtusely triangular overall, but rounded anteriorly. Postorbital margins of head aligned nearly in parallel from dorsal view. Enlarged jaw musculature slightly evident externally on dorsal surface of postorbital portion of head.

Opercular membrane attaching to isthmus only anterior to vertical through pectoral-fin insertion. Opercular opening large; extending ventral of pectoral-fin insertion by distance equal to distance from tip of snout to middle of orbit and extending dorsal of pectoral-fin insertion by distance equal to snout length.

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-fourth of HL. Eye diameter approximately equal to one-half of snout length. Interorbital width approximately equal to 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 ventral of horizontal extending through tip of snout and along horizontal extending through maxillary-barbel origin. Distance between anterior nares approximately equal to distance from tip of snout to middle of eye. Posterior narial opening situated on dorsal surface of head, located along vertical through anterior margin of orbit; opening nearly round and nearly completely surrounded by flap of skin, with anterior portion highest and with narrow gap posteriorly between margins of flap.

Mouth inferior; its width approximately one-half of HL. Margin of lower jaw gently rounded; its posterior border reaching to vertical through posterior margin of orbit. Premaxillary tooth patch in form of gently-arched band. Band of teeth continuous across midline with anterior margin convex and posterior margin concave and running in parallel to anterior margin.Teeth on premaxilla small, conical, sharply-pointed, and arranged in four regular rows. Vomerine teeth arranged in contralateral tooth patches located on each side of midline, with patches obliquely-aligned and separated at midline by distance equivalent to width of one or two vomerine teeth. Vomerine teeth similar in form and size to those on premaxilla, with one row medially and two rows laterally. Dentary teeth comparable in size and shape to premaxillary teeth. Dentary dentition consisting of four tooth rows medially that taper to two rows laterally.

Maxillary barbel slender, its length approximately equal to distance from tip of snout to posterior margin of orbit. Maxillary-barbel origin located ventral to middle of orbit. Mental barbels approximately equal in length to maxillary barbel and to each other. Medial mental-barbel origin located at vertical through rictus. Lateral mental-barbel origin situated only slightly posterior to medial mental-barbel origin. Tips of adpressed mental barbels falling short of posterior margin of opercle.

Dorsal-fin size moderate overall with length of dorsal-fin base approximately 0.39-0.40 of HL. Longest dorsal-fin ray, excluding distal filament, equal in length to slightly less than two-thirds of HL. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous and with short, distal filament in all available, apparently male, specimens. Distal margin of dorsal fin straight, with first ray longest. Dorsal-fin origin located at approximately anterior 0.30 of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin falling slightly short of vertical through tip of adpressed pelvic fin but reaching to vertical through vent. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

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

Base of anal fin comparatively long. Anal-fin origin located well posterior of middle of SL.Anal-fin margin distinctly convex along entire length in all available, apparently male, specimens. Posterior most unbranched and anterior two-thirds of branched anal-fin rays of nearly equal length, with subsequent fin rays becoming gradually shorter. Posterior most anal-fin ray without posterior, membranous attachment to body.

Pelvic fin comparatively long, its distal margin nearly straight, with first branched ray longest. Pelvic-fin insertion located distinctly anterior of middle of SL and along vertical through posterior portion of base of dorsal fin. Tip of adpressed pelvic fin extending posterior of middle of SL and nearly to anal-fin origin. Medial most pelvic-fin ray with membranous attachment to body for basal two-thirds of its length.

Pectoral-fin length approximately two-thirds of HL. Pectoral-fin margin very slightly concave anteriorly and then convex along rest of margin, with first ray longest. First pectoral-fin ray not spinous but with very short distal filament in all available, apparently male, specimens.

Coloration in alcohol. Head and body with scattered, dark pigmentation over dorsal and lateral surfaces with overall coloration somewhat darker dorsally. Abdomen and underside of head and snout without dark pigmentation. Blotch of darker pigmentation present on lateral surface of body located in area immediately posterior of opercle and dorsal to basal one-half of adpressed pectoral fin. Sides of head with distinct boundary between dorsal pigmented and ventral unpigmented regions, boundary extending from horizontal extending through base of maxillary barbel posteriorly to base of operculum. Posterior margin of opercle sparsely pigmented.

Dorsal fin covered with scattered, dark spots; fin more intensely pigmented on basal one-half and along entire length of membrane between first and second fin rays. Anal fin with scattered, dark pigmentation on basal portions of fin rays and interradial membranes, but with margin of fin clear. Caudal fin dusky throughout. Pectoral fin with scattered, dark pigmentation on basal one-half of dorsal surface but lacking dark pigmentation on ventral surface. Pelvic fin with sparse, scattered, dark pigmentation basally.

All barbels with scattered, small, dark spots of pigmentation basally and otherwise pale.

Sexual dimorphism. All available specimens of Paracetopsis atahualpa are apparently mature males as evidenced by the distal filaments on the first fin rays of the dorsal and anal fins and in the convex margin of the anal fin. These features are characteristic of mature males in those species of the Cetopsinae that demonstrate sexual dimorphism.

Distribution. Paracetopsis atahualpa is only known from the Pacific Ocean versant río Tumbes basin in northwestern Peru and the adjoining upper reaches of the río Zarumilla basin in southwestern Ecuador ( Fig. 55 ).

Etymology. The species name, atahualpa , is in reference to Atahualpa who reigned from 1515 to 1533 as the last ruler of the Inca Empire that encompassed the region from which the population samples of this species originated.

Remarks. Chang & Ortega (1995: 4) reported Paracetopsis bleekeri from Tumbes Department of northwestern Peru. This record was presumably based on the examination of MUSM 5507 and MUSM 5508, the only specimens of the species then available to those authors. Examination of those specimens reveals that they are rather P. atahualpa , a very similar species that, nonetheless, differs from P. bleekeri on the basis of the features cited in the “Diagnosis”.

Material examined. 7 specimens (128-242 mm SL). Holotype. Peru. Tumbes: río Tumbes, Cabo Inga (3°58’00"S, 80°24’59"W), M. Napravnik et al., 8 January 1997, MUSM 11560 , 1 (128) . Paratypes. Peru. Tumbes: río Tumbes, Cabo Inga (3°58’00"S, 80°24’59"W), collected with holotype, MUSM 16360 , 2 (145- 148) , USNM 361717 , 1 (153) . Cabo Inga, río Tumbes at its confluence with Quebrada Cazaderos (5°05’S, 80°30’W), F. Chang, 10 December 1993, MUSM 5508 , 1 (242) . Río Tumbes, no specific locality, H. Gutierrez, MUSM 5507 , 16 November 1978, 1 (210). Ecuador. El Oro: Portovelo (approximately 3°43’S, 79°37’W, apparently upper portions of río Zarumilla system), J. N. Rose, 13 October 1918, USNM 83530 , 1 (155).

Figures

Fig. 54. Paracetopsis atahualpa, new species, holotype, MUSM 11560, 128 mm SL; Peru, Tumbes, río Tumbes, Cabo Inga (3°58’00"S, 80°24’59"W).

Fig. 55. Map of northwestern South America showing geographic distribution of Paracetopsis atahualpa (1 = holotype locality), Paracetopsis bleekeri (2 = neotype locality; also holotype locality for Cetopsis occidentalis), and Paracetopsis esmeraldas (3 = holotype locality) (some symbols represent more that one locality and/or lot of specimens).