Cetopsis baudoensis (Dahl, 1960)

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 : 155-157

Cetopsis baudoensis (Dahl, 1960)

Figs. 12 , 14 , Tables 9 -15

Pseudocetopsis baudoênsis Dahl, 1960b: 452 , unnumbered Fig. on page 453 [type locality: ( Colombia): Quitasol , Baudó ; also reported from Amparraidó, Baudó].– Vari & Ferraris, 2003: 258 [in check list; distribution].

Pseudocetopsis baudoensis .– Cala, 1981: 4 [in listing of type specimens in ICN-MHN with citations of catalog numbers].

Hemicetopsis amphiloxa [not of Eigenmann, 1912].–Mojica- C., 1999: 565 [in part, citation of species from Colombia, río Baudó].

Diagnosis. Cetopsis baudoensis can be distinguished from all of its congeners by the combination of the presence of an eye, the 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 wide mouth with its width equal to one-half of HL, the absence of a 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, the possession of small dark spots on the lateral and dorsal surfaces of the body, the absence of eye-size or larger spots on the body, the possession of 9, rarely 10, pectoral-fin rays, 18 to 20 preanal vertebrae, 14 to 16 precaudal vertebrae, 33 to 35 caudal vertebrae, 47 to 49 caudal vertebrae, 20 to 22 branched anal-fin rays, and 23 to 27 total analfin rays.

Description. Body moderately deep, slightly transversely compressed laterally anteriorly, becoming increasingly compressed posteriorly. Body depth at dorsal-fin origin equal to HL and approximately 0.27 of SL. Lateral line on body complete, unbranched, and midlateral; extending from vertical through pectoral-fin base onto hypural plate with slight dorsal bend on hypural plate. Lateral line terminating at, or slightly posterior of, posterior margin of hypural plate. Dorsal profile of body straight and distinctly inclined from nape to dorsalfin origin; nearly straight from dorsal-fin origin to caudal-fin base. Ventral profile of body slightly convex along abdomen, approximately straight, but posterodorsally-slanted along base of anal fin. Caudal-peduncle depth slightly less than caudal-peduncle length.

Head triangular overall in lateral view and broadly rounded anteriorly. Dorsal profile of head convex from tip of snout to vertical through posterior nares and straight from that point to posterior of nape. Ventral profile of head gently convex. Profile of snout in dorsal view obtusely triangular and rounded at tip. Portion of head posterior of nares with lateral profiles diverging slightly posteriorly from dorsal view. Dorsal surface of posterior portion of head without enlarged jaw musculature externally apparent.

Opercular membrane attaching to isthmus as far as point slightly anterior of vertical through pectoral-fin insertion. Opercular opening relatively wide; extending ventral of pectoral-fin insertion by distance approximately equal to distance from tip of snout to posterior margin of orbit and extending dorsal of pectoral-fin insertion by distance approximately equal to snout length.

Eyes 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 slightly anterior of one-fourth of HL. Eye diameter approximately two-thirds 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 at horizontal extending through tip of snout and slightly dorsal to horizontal running through maxillary-barbel origin. Distance between anterior nares approximately equal to distance from anterior to posterior nares, and approximately equal to snout length. Posterior narial opening large; located near dorsal profile of head and dorsal to anterior one-half of orbit; opening rounded, with anterior two-thirds of aperture bordered by flap of skin. Distance between contralateral posterior nares slightly less than distance between contralateral anterior nares.

Mouth inferior; its width one-half of HL. Margin of lower jaw broadly rounded, its posterior extent reaching slightly beyond vertical through middle of eye. Premaxillary tooth patch elongate, continuous across midline; anterior margin convex, posterior margin concave and running in parallel to anterior margin. Premaxillary teeth moderate, conical, and sharply-pointed, with teeth arranged in three rows across entire tooth patch. Teeth of all tooth rows of approximately same size. Vomerine teeth arranged in one anteriorly-convex row without medial gap. Vomerine teeth bluntly conical and distinctly larger than premaxillary teeth. Dentary with two rows of teeth. Primary dentary tooth row consisting of conical teeth of approximately same size as those on vomer. Secondary dentary tooth row shorter, located anterior of primary tooth row, and formed of 5 or 6 teeth extending laterally from each side of the symphysis.

Maxillary barbel slender, its length distinctly greater than distance from tip of snout to posterior margin of orbit and nearly equal to one-half of HL; barbel origin located near vertical through anterior margin of orbit. Mental barbels approximately equal in size and slightly shorter than maxillary barbel. 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 moderately large overall with length of dorsalfin base approximately 0.37-0.42 of HL and equal to distance from tip of snout to posterior margin of orbit. Longest dorsalfin ray, excluding filament on first dorsal-fin ray of mature males, equal in length to distance from anterior margin of eye to posterior margin of head. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous; with very slight, distal, filament in females and immature males and moderately long filament in single, available, adult male. Distal margin of dorsal fin nearly straight, with first ray longest. Dorsal-fin origin located at approximately anterior one-third of SL and along vertical through middle of adpressed pectoral fin. Tip of adpressed dorsal fin, excluding distal filament on first ray, reaching to vertical through distal one-fourth of adpressed pelvic fin. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

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

Base of anal fin moderate, approximately 0.30 of SL.Analfin origin located distinctly posterior of middle of SL. Anal-fin margin nearly straight in females and immature males, with posterior most unbranched anal-fin ray longest and lengths of subsequent rays gradually decreasing. Anal-fin margin convex in single available mature male. Posterior most analfin ray with posterior, membranous attachment to body for basal one-fifth of its length.

Pelvic fin large, with distal margin straight and first branched ray longest. Middle of adpressed pelvic fin situated at middle of SL, with origin of fin located posterior of vertical through base of dorsal fin. Tip of adpressed pelvic fin falling slightly short of vent. Medial most pelvic-fin ray with membranous attachment to body for basal two-thirds of its length.

Pectoral-fin length about two-thirds of HL. Pectoral-fin margin very slightly convex, with first ray longest. First pectoral-fin ray not spinous and with short, distal filament present only in single, available, adult male.

Coloration in alcohol. Dusky pigmentation formed by small, dark chromatophores located on dorsal and dorsolateral portions of head and body. Dusky pigmentation on body in region anterior of vertical through anal-fin origin extending ventrally beyond lateral line to horizontal extending through pectoral-fin insertion. Abdomen, underside of head, and region immediately dorsal of base of anal fin virtually without dark pigmentation. Portion of lateral surface of head ventral of horizontal extending through maxillary barbel together with underside of head without dark pigmentation. Tip of snout with limited dark pigmentation. Dorsal fin with scattered, dark pigmentation across basal portion of fin and along at least basal one-half of first fin ray. Pectoral, pelvic, and anal fins without dark pigmentation. Caudal fin with scattered, dark pigmentation across fin base, and with spots of dark pigmentation extending across basal one-half of upper lobe.

Maxillary barbel darkly pigmented for most of its length, with tip generally pale. Mental barbels either unpigmented or with scattered, dark pigmentation.

Sexual dimorphism. Mature males of Cetopsis baudoensis have the distal filament on the first ray of the dorsal fin longer than in females and immature males and with a slight filament on the first ray of the pectoral fin contrary to the absence of that structure in conspecific females and immature males. The anal-fin margin is convex in mature males contrary to being nearly straight in females and immature males.

Distribution. Cetopsis baudoensis is only known from the río Baudó basin of the Pacific Ocean versant of western Colombia ( Fig. 12 ).

Ecology. The majority of the examined specimens of Cetopsis baudoensis , (NRM 27738, 31747) were collected from a highly turbid, white-water river over clay bottoms with logs in the main channel and clay and leaves in the lower portions of the quebradas that were tributary to the main river channel. Specimens were collected at depths of 2 m or less and at an elevation of less than 50 m (S. O. Kullander, NRM; pers. commun., 2001).

Remarks. In his original description of Pseudocetopsis baudoênsis, Dahl (1960b: 452) neglected to provide the catalog numbers for the type series of the species. Cala (1981: 4) reported that the holotype of P. baudoensis, ICN-MHN 118, is 106.4 mm SL and that the four extant paratypes of the species are catalogued as ICN-MHN 100, with the largest paratype 241 mmSL.

Mojica-C. (1999: 565) reported Hemicetopsis amphiloxa (the Cetopsis amphiloxa of this paper) from the río Baudó. That record presumably refers to Cetopsis baudoensis that is the only member of the Cetopsinae known from that river basin. Further support for this supposition comes from the fact that Cetopsis baudoensis was not cited as a recognized species by Mojica-C. (1999) in his compilation of the species of the Cetopsinae of Colombia.

Material examined. 15 specimens (54-187 mm SL). Colombia. Choco : río Baudó drainage, Boca de Pepé, various tributaries and river close to village (5°04’N, 77°03’W), NRM 27738, 12 (54-98) ; NRM 31747 , 1 specimen cleared and stained, originally part of NRM 27738 ). Pizarrro (4°58’N, 77°22’W), FMNH 70339 , 2 (163- 187, smaller specimen adult male).

Figures

Fig. 12. Map of central and northern SouthAmerica showing geographic distribution of Cetopsis amphiloxa (1 = holotype locality of Hemicetopsis amphiloxus), Cetopsis arcana (2 = holotype locality), Cetopsis baudoensis (3 = holotype locality of Pseudocetopsis baudoênsis), Cetopsis caiapo (4 = holotype locality), and Cetopsis candiru (type locality inexact = rivers of Equatorial Brazil) (some symbols represent more that one locality and/or lot of specimens).

Fig. 14. Cetopsis baudoensis, NRM 27738, 98 mm SL; Colombia, Choco, río Baudó drainage, Boca de Pepé, various tributaries and river close to village (5°04’N, 77°03’W).