Cetopsis starnesi, 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 : 199-201

publication ID

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



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scientific name

Cetopsis starnesi

new species

Cetopsis starnesi , new species

Figs. 41 View Fig , 43 View Fig , Tables 9 -15

Diagnosis. Cetopsis starnesi 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, the presence of approximately eye-size, dark spots on the lateral surface of the body, the absence of finely-scattered, dark pigmentation across the lateral and anterior surfaces of the snout, and the possession of 22 or 23 branched anal-fin rays. It is further distinguished from the externally very similar C. umbrosa in the number of precaudal vertebrae (11 or 12 versus 14, respectively), caudal vertebrae (33 versus 30, respectively), and total anal-fin rays (27 or 28 versus 26, respectively).

Description. Body moderately stout, slightly laterally-compressed anteriorly and becoming progressively distinctlycompressed posteriorly. Body depth at dorsal-fin origin approximately 0.24 of SL and approximately equal to HL. Lateral line on body complete, unbranched, and midlateral; extending from vertical through pectoral-fin base onto, and very slightly upturned on, hypural plate and terminating prior to posterior margin of hypural plate. Dorsal profile of body approximately 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 approximately equal to, or slightly greater than, caudal-peduncle length.

Head in profile acutely triangular overall with bluntlyrounded snout. Dorsal profile of head slightly convex anteriorly and straight from posterior limit of snout to nape. Ventral profile of head slightly convex. Margin of snout bluntly triangular in dorsal view. 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 to region anterior to 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 orbit, 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-fourth of HL. Eye diameter approximately two-thirds 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, 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 regular rows. Vomerine teeth arranged in single, irregular row continuous across midline. Vomerine teeth stout, conical, and much larger than teeth on premaxilla and dentary. Dentary teeth comparable in shape to, but larger in size than, premaxillary teeth. Dentary dentition consisting of 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 margin of orbit, but less than one-half of HL; barbel origin located ventral to 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 origin of medial mental barbel. Tips of adpressed mental barbels falling distinctly short of posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.39-0.41 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 but with distal filament present in male holotype (condition in female paratype undeterminable because of damage to fin). Distal margin of dorsal fin sinusoidal, with anterior portion concave and posterior portion convex. Dorsal-fin origin located at approximately anterior 0.33-0.35 of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin, excluding distal filament present on first ray in mature males, reaching nearly to vertical through anal-fin origin. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal fin moderately-forked, symmetrical; tips of lobes apparently pointed. Length of longest caudal-fin ray approximately one and three-fourths times length of middle fin rays.

Base of anal fin moderately long. Anal-fin origin located distinctly posterior of middle of SL. Anal-fin margin straight in female paratype, with posterior most unbranched anal-fin ray longest and subsequent rays becoming gradually shorter. Anal-fin margin distinctly convex in single, examined mature male specimen (holotype). 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 along vertical through posterior of base of dorsal fin. Tip of adpressed pelvic fin extending to middle of SL, but falling slightly 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. Pectoral-fin margin nearly straight laterally and convex medially, with first ray longest and prolonged into distal filament in both sexes, with filament proportionally longer in male holotype than female paratype. First pectoral-fin ray not spinous.

Coloration in alcohol. Overall coloration of head and body in female paratype darker than in male holotype. Dorsal portion of head dark from interorbital region to rear of head. Ventral surface of head pale. Snout pale from tip to posterior nares in male, but somewhat dusky, albeit lighter than remaining dorsal portion of head, in female. Lips pale in male, slightly dusky in female. Dorsal portion of body dark in both sexes. Ground coloration of lateral surface of body pale and overlain by scattered, approximately eye-size, dark spots. Spots more concentrated dorsally and on caudal peduncle. Spots coalesce into irregular blotches, more so in larger specimen female paratype. Ventral surface of body pale.

Dorsal fin in male holotype with semicircular dusky region basally and with dusky interradial membrane between first and second rays and remainder of fin pale. Dark pigmentation on dorsal fin in female paratype more intense but similar distribution. Caudal fin with dark, bilobed spot extending from base of branched fin-rays posteriorly approximately to vertical through middle of length of middle fin rays. Middle caudal-fin rays posterior of bilobed spot unpigmented, remaining fin rays in region distal of basal spot dusky. Anal fin of female dusky basally and remainder of fin hyaline. Anal fin of male hyaline throughout. Pectoral and pelvic fins pale.

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

Sexual dimorphism. The single examined male of Cetopsis starnesi has the filaments on the pectoral fins proportionally more elongate than are the extensions present in the one examined female of the species. The sexually-dimorphic difference in the degree of the development of the filament on the dorsal fin that is typical of many species in the Cetopsinae cannot be evaluated for C. starnesi as a consequence of the damage to the dorsal fin in the single available female (the paratype). The anal-fin margin is distinctly convex in the male in contrast to the straight margin that is present in the female.

Distribution. Cetopsis starnesi is only known from two localities in southeastern Bolivia, the holotype locality (USNM 314309) in the far northwestern portions of the río de La Plata basin and the site where the female paratype (CBF 887) was captured in the far southern reaches of the upper rio Madeira basin ( Fig. 41 View Fig ).

Etymology. The species name, starnesi , is in reference, Dr. Wayne C. Starnes, of the North Carolina State Museum of Natural History, who collected the type-series of this species along with numerous other specimens of fishes that have proved very useful in this and other studies.

Remarks. The distribution of Cetopsis starnesi across the divide between the upper rio Madeira of the rio Amazonas basin and the río de La Plata system is uncommon amongst components of the lowland to mid-elevation Neotropical ichthyofauna that have been critically studied to date. Such a distribution across that drainage divide, nonetheless, occurs occasionally in species of various groups that have been studied in recent decades including the freshwater needlefish Potamorrhaphis eigenmanni ( Collette, 1982: 738) , the cichlids Mesonauta festivus and Astronotus crassipinnis ( Kullander, 1986: 37) , and the curimatid characiform Psectrogaster curviventris ( Vari, 1989a: 31) .

Pozzi (1945: 262 and map on page 251) reported Cetopsis caecutiens (= coecutiens ) from two localities in northern Argentina, apparently in the río Bermejo basin in the Provinces of Salta and Jujuy. This record by Pozzi was presumably the basis for the later citation of C. coecutiens as a component of the Argentinean ichthyofauna by Ringuelet & Arámburu (1961: 46). Subsequently, Ringuelet et al. (1967: 348) specifically noted that the inclusion of this species in their compendium of the freshwater fishes of Argentina was based on Pozzi (1945) but cited C. coecutiens as being present in the Provinces of Salta and Catamarca, rather than Salta and Jujuy as indicated by Pozzi (1945). Specimens of the Cetopsinae examined during this study did not include any samples of C. coecutiens that originated at any locality within the río de La Plata basin. Furthermore, the only species of the Cetopsinae that we examined that originated in the río Bermejo basin was C. starnesi . In light of the available information we tentatively consider the citations of C. coecutiens from northern Argentina by Pozzi (1945), Ringuelet & Arámburu (1961) and Ringuelet et al. (1967) to refer to C. starnesi .

Castello (1969: 407) reported Pseudocetopsis gobioides from a locality close to the junctions of the río San Antonio and río Bermejo in the Province of Salta, northwestern Argentina. Although Cetopsis gobioides does occur in Argentina in the Provinces of Misiones (MHNG 2389.14), Corrientes ( Alonso de Arámburu et al., 1962: 237), and Santa Fe (Oliveros & Rossi, 1992: 77), all of which are located in the northeastern portions of that country, there are no confirmed records of the occurrence of C. gobioides in northwestern Argentina. Neither for that matter are there any records of the latter species from an upland region comparable to that from which the specimens reported by Castello (1969) originated. As noted above the only member of the Cetopsinae known to occur in the río Bermejo basin is Cetopsis starnesi and in light of the available information we consider the report of Pseudocetopsis gobioides from that river system by Castello (1969) to refer to C. starnesi .

Material examined. 2 specimens (77-97 mm SL). Holotype. Bolivia. Tarija: Argentinean-Bolivian border, río Bermejo, 4-5 km S of Pueblo Salado, approximately 30 air km S of Bermejo (22°27’S, 64°32’W), W. C. Starnes et al., 5 October 1988, USNM 314309 View Materials , 1 View Materials GoogleMaps , mature male (77). Paratype. Bolivia. Chuquisaca: río Azero , below road crossing, approximately 35 air km SE of Padilla (19°37’S, 64°04’W), W. C. Starnes et al., 28 September 1988, CBF 887 View Materials , 1 View Materials GoogleMaps , female (97, formerly USNM 314309 View Materials ) .