Cetopsis pearsoni, 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 : 189-191

Cetopsis pearsoni , new species

Figs. 33 , 36 , Tables 9 -15

Pseudocetopsis sp. – Lauzanne et al., 1991: 69 [ Bolivia, Bolivian Amazon, region of Yucumo].

Diagnosis. Cetopsis pearsoni can be distinguished from all of its congeners by the combination of the presence of an eye, the conical teeth on the vomer and the dentary, the rounded posterior nares that is distinctly separated from the contralateral nares by a distance greater than the width of the posterior nares, the absence of a dark humeral spot, the presence of a posteriorly-rounded, variably-developed, bilobed patch of dark pigmentation at the base of the caudal fin, the absence of a spot of dark pigmentation on the base of the dorsal fin, the absence of prominent dark pigmentation along the membrane behind the first ray of the dorsal fin, and the combination of the presence of fine spotting on the dorsolateral and lateral surfaces of the body, and the lack of approximately eye-size, dark spots on the lateral surface of the body.

Description. Body moderately stout, slightly laterally compressed anteriorly and becoming progressively distinctlycompressed posteriorly. Body depth at dorsal-fin origin approximately 0.22 of SL, and distinctly shorter than HL. Lateral line on body complete, unbranched, and midlateral; extending from vertical through pectoral-fin base onto, and slightly upturned on, hypural plate and terminating prior to posterior margin of hypural plate. Dorsal profile of body nearly straight from nape to dorsal-fin origin and straight from dorsal-fin origin to caudal-fin base. Ventral profile of body convex along abdomen, approximately straight, but posterodorsally slanted, along base of anal fin. Caudal-peduncle depth slightly greater than caudal-peduncle length.

Head in profile acutely triangular overall with bluntlyrounded snout. Dorsal profile of head with rounded snout and then straight from above orbit to nape. Ventral profile of head slightly convex. Margin of snout in dorsal view bluntly triangular. Postorbital margins of head running 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 in region anterior to vertical through pectoral-fin insertion. Opercular opening moderate; extending ventral of pectoral-fin insertion by distance equal to snout length and extending dorsal of pectoral-fin insertion by distance slightly less than 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 located at approximately anterior one-third of HL. Eye diameter approximately equal to one-half of snout length. Interorbital width approximately equal to distance from tip of snout to middle of eye. Anterior narial opening circular, surrounded by short, anteriorly-directed, tubular rim of skin. Opening of anterior nares located along horizontal extending through both tip of snout and maxillary-barbel origin. Distance between anterior nares approximately equal to snout length. Posterior narial opening located on dorsal surface of head, and situated along vertical through anterior margin of orbit; narial opening nearly round with anterior two-thirds of aperture surrounded by flap of skin with anterior portion of flap highest.

Mouth inferior; its width slightly less than 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 and 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 three or four, irregular rows. Innermost row of premaxillary teeth slightly larger than those in other rows. Vomerine teeth arranged in single, irregular row continuous across midline. Vomerine teeth stout, conical, and much larger than teeth on premaxilla or dentary. Dentary teeth comparable in shape to, but larger in size than, premaxillary teeth, with three, irregularly-arranged rows medially that taper to one row laterally.

Maxillary barbel slender, its length greater than distance from tip of snout to posterior of orbit, but distinctly less than one-half of HL; barbel origin located ventral of middle of orbit. Mental barbels approximately equal in length to each other but shorter than 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 barbels falling far short of posterior margin of opercle.

Dorsal fin moderately large overall, with length of dorsalfin base approximately 0.40-0.42 of HL. Length of longest branched dorsal-fin ray equal to two-thirds of HL. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous and with distal filament in both sexes, but with filament proportionally longer in mature males ( Fig. 36 ). Distal margin of dorsal fin concave, with first ray longest. Dorsal-fin origin located at approximately anterior 0.33-0.34 of SL and along vertical extending through distal one-fourth of adpressed pectoral fin. Tip of adpressed dorsal fin, excluding distal filament on first fin ray, reaching nearly to vertical through vent. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal fin shallowly-forked, symmetrical; tips of lobes pointed. 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 well posterior of middle of SL, and slightly anterior of vertical through middle of TL. Anal-fin margin straight in females and immature males with posterior most unbranched anal-fin ray longest, and subsequent rays becoming gradually shorter. Anal-fin margin slightly convex in mature males. Posterior most anal-fin ray without posterior, membranous attachment to body.

Pelvic fin moderate; distal margin nearly straight, with first ray longest. Pelvic-fin insertion located anterior to middle of SL and situated ventral to posterior one-half of base of dorsal fin. Tip of adpressed pelvic fin extending to vertical through middle of SL and falling short of anterior limit of vent. Medial most pelvic-fin ray with membranous attachment to body along basal two-thirds of its length.

Pectoral-fin length approximately two-thirds of HL. First pectoral-fin ray not spinous but prolonged into distal filament, filament very short in females and moderately-elongate in mature males ( Fig. 36 ). Pectoral-fin margin sinusoidal overall with lateral portion concave and medial region convex.

Coloration in alcohol. Dorsal portion of head dark from interorbital region to posterior of head. Snout pale from tip to proximate to posterior nares. Lips and ventral portions of head pale. Dorsal portion of body dark. Lateral surface of body pale overall, but covered with fine, dark spots at least dorsolaterally. Fine, dark spots extending further ventrally in region above posterior one-half of base of anal fin and on caudal peduncle. Spots sometimes coalesce, but with conjoined spots distinctly smaller than size of eye. Ventral surface of body pale.

Dorsal fin with some scattered, dark pigmentation basally, but without distinct basal spot; darker specimens with dusky region extending further distally on fin. Remainder of dorsal fin pale. Caudal fin with scattered, dark pigmentation along base of principal fin-rays. Dark bilobed spot extending from base of branched fin rays posteriorly approximately to vertical through middle of length of innermost rays; spot more obvious in more darkly pigmented individuals. Remainder of caudal fin pale, but dusky in more darkly pigmented specimens. Pectoral and pelvic fins pale or with scattered pigmentation, dark on dorsal surfaces. Anal fin pale or with scattered, dark pigmentation basally.

Barbels dusky on basal one-half of anterior surface and otherwise pale.

Sexual dimorphism. Mature males of Cetopsis pearsoni have a filament on the first ray of the dorsal and pectoral fins that is proportionally more elongate than the comparable structures present in conspecific females. Mature males of the species also have slightly convex margins of the anal fin rather than the straight fin margin of conspecific females and immature males.

Distribution. Cetopsis pearsoni occurs in the upper portions of the rio Madeira drainage basin in southeastern Peru and northeastern Bolivia ( Fig. 33 ).

Etymology. The species name, pearsoni , is in honor of Nathan E. Pearson whose collecting efforts during 1921 in the region from which the species is known documented the high diversity of the ichthyofauna in that area.

Remarks. Perugia’s (1897: 23) report of Cetopsis plumbeus as a component of the Bolivian ichthyofauna was evidently the basis for subsequent citations of that species for that fish fauna, in various genera, by Fowler (1940b: 97; 1945: 5) and Terrazas-Urquidi (1970: 21). The specimen that served as the basis for Perugia’s citation was unavailable for examination during this study rendering a definitive identification of that material impossible. Although C. plumbea is indeed present in northeastern Bolivia, C. pearsoni , an externally similar species, also occurs in that region. As such Perugia’s citation could potentially represent either of these two species.

An examination of at least some of the specimens that served as the basis for the citation of Pseudocetopsis sp. from various localities in Bolivia by Lauzanne et al. (1991: 69) demonstrated that they are Cetopsis pearsoni , a species that is described as new herein.

Chang (1998: 26) reported “ Pseudocetopsis sp. n. ” from the río Tambopata and río Távara in the Tambopata-Candamo Reserved Zone, Madre de Dios, in southeastern Peru. It is likely that this report is based, at least in part, on the specimen that is herein designated as the holotype of Cetopsis pearsoni . That citation may, however, also be partially based on C. plumbea , a species that was also collected in, and reported from, those river systems by Chang (1998).

One specimen from considerably downstream of the known distribution of Cetopsis pearsoni either represents that species or a closely related, and possibly undescribed, form. That specimen cannot be definitively identified as a consequence of its condition (see comments concerning INPA 8485 in “Remarks” under C. montana ).

Material examined. 13 specimens (38-114 mm SL). Holotype. Peru. Puno: Provincia de Sandia, río Candamo, Zona Reserva Tambopata (13°28.97’S, 69°50.08’W), 358 m elevation, F. Chang, 1 April 1997, MUSM 11093 , 1 , mature male (90). Paratypes. 11 specimens (50-114 mm SL). Bolivia, Beni: río Mamoré system, río Yacuma, San Borja (14°09’S, 66°51’W), L. Lauzanne & G. Loubens, 1982, MNHN 1988-1995 , 1 (110) . Río Mamoré , Trinidad (14°47’S, 64°47’W), L. Lauzanne & G. Loubens, 1984, MNHN 1988-2012 , 1 (54) . Cochabamba: río Mamoré, Chapare, Villa Tunari (16°55’S, 65°22’W), L. Lauzanne & G. Loubens, 1982, MNHN 1988-1998 , 3 (50-107, one mature male 70 mm SL) . Río Mamoré, Chapare, Villa Tunari (16°55’S, 65°22’W), L. Lauzanne & G. Loubens, 20 Jun 1983, MZUSP 27812 , 6 (57-114; 1 specimen, 59 mm, cleared and stained) . Non-type specimen . 1 specimen (1, 38 mm SL). Bolivia Pando: no specific locality, FMNH 106906 , 1 (38).

Figures

Fig. 33. Map of central and northern SouthAmerica showing geographic distribution of Cetopsis orinoco (1 = holotype locality of Pseudocetopsis plumbeus orinoco), Cetopsis othonops (2 = holotype locality of Hemicetopsis othonops), Cetopsis parma (3 = holotype locality), Cetopsis pearsoni (4 = holotype locality), and Cetopsis plumbea (5 = lectotype locality of Cetopsis plumbeus) (some symbols represent more that one locality and/or lot of specimens).

Fig. 36. Cetopsis pearsoni, new species, holotype, mature male, MUSM 11093, 90 mm SL; Peru, Puno, Provincia de Sandia, río Candamo, Zona Reservada Tambopata-Candamo (13°28.97’S, 69°50.08’W).