Cetopsis caiapo, 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 : 157-159

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https://doi.org/ 10.1590/S1679-62252005000200001

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scientific name

Cetopsis caiapo

new species

Cetopsis caiapo , new species

Figs. 12 View Fig , 15 View Fig , Tables 9 -15

Diagnosis. Cetopsis caiapo can be distinguished from all of its congeners by the combination of the presence of an eye, the large conical teeth on the vomer and 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 dark humeral spot, the absence of a posteriorly-rounded, variably-developed, bilobed patch of dark pigmentation at the base of the caudal fin, the absence of a band of dark pigmentation along the distal portions of the anal fin, and the possession of 44 total vertebrae, 29 caudal vertebrae, 22 total anal-fin rays, and 18 branched anal-fin rays.

Description. Body relatively rounded transversely, somewhat compressed anteriorly, becoming increasingly compressed posteriorly. Body depth at dorsal-fin origin approximately 0.29 of SL, and approximately equal to 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, nearly 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 approximately twice caudal-peduncle length.

Head triangular in lateral view and tapering to blunt point anteriorly. Dorsal profile of head slightly convex from tip of snout to vertical though posterior margin of eye, nearly straight from that point to posterior margin of head. Ventral profile of head slightly convex. Profile of snout in dorsal view acutely-pointed, with rounded tip. Width of head gradually increasing posterior of orbit. Dorsal surface of postorbital part of head dominated by enlarged, externally apparent, jaw musculature in form of bilateral, convex swellings extending from orbit to nape. Eye obscured by thick, overlying, integumentary tissues, but, nonetheless, apparent with close inspection.

Opercular membrane attaching to isthmus as far posteriorly as vertical through pectoral-fin insertion. Opercular opening relatively large; extending ventral 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-third of HL. Eye diameter approximately 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 at horizontal extending through maxillary-barbel origin. Distance between anterior nares approximately equal to snout length. Posterior narial opening positioned on dorsal surface of head, located along vertical through anterior margin of orbit; opening slightly ovoid, with long axis of aperture aligned parallel to body axis. Anterior two-thirds of posterior narial opening bordered by flap of skin, with flap highest anteriorly. Distance between contralateral posterior nares slightly less than distance between contralateral anterior nares.

Mouth inferior; its width approximately one-half of HL. Margin of lower jaw broadly rounded, its posterior extent reaching vertical through posterior margin of orbit. Premaxillary tooth patch elongate and continuous across midline with anterior margin convex and posterior margin nearly straight. Premaxillary teeth small, conical, and sharply-pointed, with teeth arranged in five or six irregularly-arranged rows. Vomerine teeth arranged in one anteriorly-convex row with length of vomerine tooth row approximately equal to that of premaxillary tooth patch. Vomerine teeth large and bluntly conical. Dentary with single row of large, conical teeth approximately equal in size and number to teeth on vomer.

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 size and length to maxillary barbel and to each other. Medial mental-barbel origin located along vertical through posterior margin of orbit. Lateral mental-barbel origin located slightly posterior of vertical through posterior margin of orbit. Tips of adpressed mental barbels falling short of posterior margin of opercle.

Dorsal fin relatively small overall, with length of dorsalfin base approximately 0.43-0.48 of HL. Length of longest dorsal-fin ray equal to length of post-orbital portion of head. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous and lacking distal filament. Distal margin of dorsal fin straight, with first ray longest. Dorsal-fin origin located at approximately anterior one-third of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin reaching to vertical through middle of pelvic-fin base. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

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

Base of anal fin comparatively short. Anal-fin origin located well posterior of middle of SL, and approximately at middle of TL. Anal-fin margin nearly straight. Posterior most unbranched anal-fin ray longest, with subsequent rays gradually becoming shorter. Posterior most anal-fin ray without posterior, membranous attachment to body.

Pelvic fin short, rounded, with first branched ray longest. Pelvic-fin insertion located anterior to middle of SL and posterior to vertical through posterior terminus of base of dorsal fin. Tip of adpressed pelvic fin extending beyond middle of SL, but falling short of vent. Medial most pelvic-fin ray with membranous attachment to body for basal one-half of its length.

Pectoral-fin length approximately one-half of HL. Pectoral-fin margin convex with first ray longest. First pectoral-fin ray not spinous and without distal filament.

Coloration in alcohol. Scattered, dark pigmentation present on most surfaces of head and body, with dark pigmentation slightly more concentrated dorsally. Dark pigmentation absent on ventral surface of head and abdomen. Dark humeral mark, several times larger than eye diameter, situated immediately posterior of membrane on opercle and dorsal to pectoral-fin base (note: holotype, the only known specimen, bleached on left side of head and body and therefore dark blotch on opercle not apparent in Fig. 15 View Fig ).

Caudal-fin base with scattered, dark pigmentation. Other fins lack dark pigmentation.

Barbels pale.

Sexual dimorphism. The single known specimen of Cetopsis caiapo , of unknown sex, does not demonstrate the sexuallydimorphic modifications of the form of the dorsal, anal, and pectoral fins that are present in mature males of many species of the Cetopsinae .

Distribution. Cetopsis caiapo is only known from one locality in the rio Tocantins basin, Brazil ( Fig. 12 View Fig ).

Etymology. The species name, caiapo , is in reference to the Caiapo Amerindian tribe that historically inhabited the area of the rio Tocantins drainage system from which the holotype of the species originated.

Material examined. 1 specimen (1, 69 mm SL). Holotype. Brazil. Goiás: Município de Minaçu / Cavalcante, rio Tocantins, at location of the future dam of the Usina Hidroeléletrica Serra da Mesa (13°50’S, 48°19’W); D. F. Moraes et al., 24 to 31 July1988, MNRJ 13236 View Materials , 1 View Materials (69.0). GoogleMaps