Cetopsis sarcodes, 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 : 197-199

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

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scientific name

Cetopsis sarcodes

new species

Cetopsis sarcodes , new species

Figs. 41-42 View Fig View Fig , Tables 9 -15

Diagnosis. Cetopsis sarcodes 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 presence of a humeral spot, the lack of a pattern of dark pigmentation across the pectoral and pelvic fins other than for a thin clear margin on each fin, the absence of distinct, dark pigmentation on the anal and caudal fins particularly on the distal portions of those fins, and the possession of 21 branched anal-fin rays, 28 caudal vertebrae, 43 total vertebrae, 25 total anal-fin rays, and 9 pectoral-fin rays.

Description. Body stout, somewhat laterally compressed anteriorly, becoming increasingly compressed posteriorly. Body depth at dorsal-fin origin approximately 0.31 of SL and equal to HL. Lateral line on body complete, unbranched, and midlateral; extending from vertical through pectoral-fin base to hypural plate. Dorsal profile of body slightly convex and obliquely-slanted from nape to dorsal-fin origin, 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 equal to caudal-peduncle length.

Head in lateral view acutely triangular with bluntly-rounded snout. Dorsal profile of head slightly convex from tip of snout to vertical through anterior margin of eye, nearly straight from that line to nape. Ventral profile of head convex. Profile of snout bluntly triangular in dorsal view. Width of postorbital portion of head gradually increases posteriorly. Dorsal surface of postorbital part of head with enlarged jaw musculature evident externally but not pronounced.

Opercular membrane attaching to isthmus as far posteriorly as vertical through pectoral-fin insertion. Opercular opening moderate, extending ventral of horizontal extending through pectoral-fin insertion for distance equal to snout length and dorsal of that level for distance approximately two-thirds of snout length.

Eye situated on lateral surface of head; located dorsal of horizontal extending through pectoral-fin insertion; eye visible in dorsal view, but not in ventral view, of head. Middle of orbit located at slightly less than anterior one-third of HL. Eye diameter approximately 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 maxillary-barbel origin. 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 along vertical through anterior margin of orbit; opening approximately round and without obvious long axis. Anterior two-thirds of posterior narial opening bordered by approximately uniformly high flap of skin. Distance between contralateral posterior nares slightly less than distance between contralateral anterior nares.

Mouth inferior, its width slightly less than one-half of HL. Margin of lower jaw broadly rounded, its posterior limit reaching to vertical through posterior margin of eye. Premaxillary tooth patch elongate, crescentic, and continuous across midline; anterior margin convex, posterior margin transverselyaligned along medial portion of tooth patch and angled posteriorly along lateral portion of patch. Premaxillary teeth relatively small, conical, and sharply-pointed, with teeth arranged in five irregularly-arranged rows medially that taper to two rows laterally. Teeth of uniform size across jaw. Vomerine teeth large, bluntly conical, and arranged in one irregular, anteriorly-convex row. Dentary dentition consisting of two rows of teeth. Primary tooth row on dentary formed of large, conical teeth slightly smaller than the teeth on the vomer. Second tooth row shorter and consisting of series of smaller teeth extending laterally from symphysis anterior to the primary tooth row. Teeth of primary row on dentary slightly smaller than those on vomer.

Maxillary barbel slender, its length approximately equal to distance from tip of snout to posterior margin of orbit; barbel origin located along vertical through anterior margin of orbit. Mental barbels approximately equal in size and length, but slightly shorter than maxillary barbel. Medial mental-barbel origin located along vertical through rictus. Origin of lateral mental barbel located slightly posterior of vertical through medial mental-barbel origin. Tips of adpressed mental barbels falling short of posterior margin of opercle.

Dorsal fin moderately large sized with length of dorsal-fin base approximately 0.40-0.43 of HL. Length of longest dorsalfin ray equal to length of postorbital region of head. Dorsalfin spinelet absent. First dorsal-fin ray not spinous; without distal, filament in single available, apparently juvenile, specimen. Distal margin of dorsal fin straight, with first ray longest. Dorsal-fin origin located at approximately anterior onethird of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin reaching to vertical through middle of adpressed pelvic fin. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

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

Base of anal fin moderately long, slightly more than onefourth of SL. Anal-fin origin located well posterior of middle of SL and slightly posterior to middle of TL. Anal-fin margin straight, with first branched anal-fin ray longest and subsequent rays becoming gradually shorter. Posterior most analfin ray without posterior, membranous attachment to body.

Pelvic fin short, with distal margin distinctly convex and first branched ray longest. Pelvic-fin insertion located anterior to middle of SL and slightly posterior to vertical through posterior portion of base of dorsal fin. Tip of adpressed pelvic fin extending beyond middle of SL and falling far short of vent. Medial most pelvic-fin ray with membranous attachment to body along 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 in single available, apparently juvenile, male.

Coloration in alcohol. Overall head and body pale, with scattered, fine, dark pigment spots scattered over dorsal and lateral surfaces of head and body. Ventral surface of head and abdomen pale. Tip of snout pale. Diffuse, dark humeral spot present on lateral surface of body dorsal to basal one-half of pectoral fin.

Dorsal, anal, and pectoral fins pale. Caudal fin with scattered, fine, dark pigmentation present at base and on basal portions of principal fin rays.

Maxillary barbel with fine, dark pigmentation basally and otherwise pale. Mental barbels pale.

Sexual dimorphism. The single available specimen of Cetopsis sarcodes is apparently a male based on the form of the genital papilla, but lacks the distal filaments of the first rays of both the dorsal and pectoral fins and the convex margin to the anal fin that are typical of mature males of many other species of the Cetopsinae . This combination of features indicates that the holotype is probably an immature male.

Distribution. Cetopsis sarcodes is known only from the type locality in the rio Tocantins basin of eastern Brazil ( Fig. 41 View Fig ).

Etymology. The species name, sarcodes , from the Greek, sarkos, for fleshy, refers to the rotund body form of this species.

Material examined. 1 specimen (69 mm SL). Holotype. Brazil. Goiás: Município de Minaçu /Cavalcante, rio Tocantins between site of future dam of Usina Hidroeléctrica Cana Brava and Ilha do Orgulho and Porto do Garimpo , D. F. Moraes Jr. et al., 10 December 1987, MNRJ 13024 View Materials , 1 View Materials (69)