Cetopsis motatanensis ( Schultz, 1944 )

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 : 176-180

Cetopsis motatanensis ( Schultz, 1944)

Figs. 25 , 27 , 28 , Tables 9 -15

Pseudocetopsis plumbeus motatanensis Schultz, 1944: 255 , pl.5, fig. b [type locality: Venezuela, río Motatán, 4 km above Motatán].–Ferraris & Vari, 1992: 16 [holotype and paratype depository].– Mago-Leccia, 1970: 82 [ Venezuela; common name].– Galvis et al., 1997: 75 [ Colombia, Lago Maracaibo basin, río Catatumbo; life history notes; common name].–Evers & Seidel, 2002: 741 [listing].

Hemicetopsis plumbeus motatanensis .– Burgess, 1989: 292 [ Venezuela, Maracaibo basin, río Motatán].

Pseudocetopsis motatanensis .– Taphorn et al., 1997: 85 [ Venezuela].–Vari & Ferraris, 2003: 258 [in check list; distribution, common name].

Pseudocetopsis plumbeus .–Mojica-C., 1999: 565 [in part, citation of species from Colombia, río Catatumbo].

Diagnosis. Cetopsis motatanensis 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 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 dark pigmentation on the distal portions of the pelvic and anal fins, the caudal fin darkly pigmented throughout other than for the narrow pale distal margin, and the possession of 18 to 20 preanal vertebrae, 15 to 17 precaudal vertebrae, 33 to 35 caudal vertebrae, 48 to 50 total vertebrae, and 9 pectoralfin rays.

Description. Body moderately-elongate, slightly-compressed anteriorly and becoming progressively distinctly-compressed posteriorly. Body depth at dorsal-fin origin approximately 0.22- 0.23 of SL, and approximately equal to distance from anterior margin of orbit to posterior margin of opercle. Lateral line on body complete, unbranched, and midlateral; extending from vertical through pectoral-fin base onto hypural plate and either straight or very slightly dorsally-directed on hypural plate. Dorsal profile of body slightly convex 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 less than caudal-peduncle length.

Head in profile acutely triangular overall with bluntlyrounded snout. Dorsal profile of head nearly straight from tip of snout to nape. Ventral profile of head slightly convex. Margin of snout rounded 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 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-fourth of HL. Eye diameter approximately equal to one-half of snout length. Interorbital width slightly greater than 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 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. Anterior two-thirds of posterior narial opening surrounded by flap of skin with anterior portion of flap highest.

Mouth inferior; its width approximately 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, 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 across tooth patch. Vomerine teeth arranged in single irregular row continuous across midline. Vomerine teeth stout, conical, and much larger than teeth on both premaxilla or dentary. Dentary teeth comparable in shape to, but larger in size than, premaxillary teeth, with two rows in series medially that taper to one row laterally.

Maxillary barbel slender, its length greater than distance from tip of snout to posterior 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 middle of adpressed medial mental barbel. Tips of adpressed mental barbels falling far short of posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsal-fin base approximately 0.48-0.52 of HL. Longest branched dorsal-fin ray, excluding distal filament on first fin ray, equal in length to two-thirds of HL. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous but with distal filament in both sexes; filament proportionally longer in mature males than in females and immature males (compare Figs. 27 and 28 ). Distal margin of dorsal fin straight, with first ray longest. Dorsal-fin origin located at approximately anterior 0.25-0.26 of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin, excluding distal filament on first ray, reaching nearly to vertical through tip of adpressed pelvic fin. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal fin moderately-forked, symmetrical; tips of lobes bluntly 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 well posterior of middle of SL, and slightly anterior of vertical through middle of TL. Anal-fin margin straight in females ( Fig. 28 ) and immature males, with posterior most unbranched analfin ray longest and subsequent rays becoming gradually shorter.Anal-fin margin very slightly convex in mature males ( Fig. 27 ). Posterior most anal-fin ray without posterior, membranous attachment to body.

Pelvic fin moderate; distal margin nearly straight, with first fin ray longest. Pelvic-fin insertion located anterior to middle of SL and along vertical through posterior terminus of base of dorsal fin. Tip of adpressed pelvic fin extending beyond middle of SL but falling far 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 very slightly concave, with first ray longest. First pectoral-fin ray not spinous but prolonged into distal filament with filament proportionally longer in mature males ( Fig. 27 ) than in conspecific females and immature males.

Coloration in alcohol. Head and body covered with dark pigmentation, darker dorsally. Dark pigmentation arranged in irregular blotches with few, distinct, eye-size, rounded, dark spots in some individuals. Ventral portions of head and abdomen pale.

Dorsal fin dusky throughout, with basal portions somewhat more heavily pigmented. Caudal fin darkly pigmented throughout, more so on posterior one-half, other than for narrow pale distal margin. Pectoral, pelvic, and anal fins with scattered, dusky pigmentation.

Barbels with scattered, dark pigmentation on basal onehalf of anterior margins and barbels otherwise pale.

Sexual dimorphism. The presumed males of Cetopsis motatanensis have the filaments on the first rays of the dorsal and pectoral fins proportionally more elongate than those present in females and immature males of the species (compare Figs. 17 and 28 ). Mature males of the species also have the anal-fin margin convex rather than straight as in the case in females and immature males.

Distribution. Cetopsis motatanensis is endemic to the rivers of the Lago Maracaibo basin of northwestern Venezuela and northeastern Colombia ( Fig. 25 ).

Common Name. Colombia: “Ciego” ( Galvis et al., 1997: 75); Venezuela: “Bagre ciego” ( Mago-Leccia, 1970: 82).

Ecology. According to Schultz (1944: 256), Cetopsis motatanensis was captured “in swiftly flowing water among rubble to coarse gravel.”

Remarks. In his original description of Pseudocetopsis plumbeus motatanensis, Schultz (1944: 255) did not delve into the basis for placing that nominal form as a subspecies of Pseudocetopsis plumbeus (Steindachner) (= Cetopsis plumbea of this study). No specimens of P. plumbeus plumbeus were cited as having been examined in Schultz’ study (1944), and the information provided for that nominal subspecies in Schultz’s key (1944: 253) to the Venezuelan members of the Cetopsinae was apparently derived from the previous literature. Cetopsis motatanensis differs from the other nominal species assigned by Schultz (1944: 255) to Pseudocetopsis plumbeus in numerous features, most notably in the pigmentation patterns of the caudal fin, and it is consequently considered herein to be a distinct species.

Material examined. 11 specimens (57.5- 155 mm SL). Venezuela. Merida: río Chama in El Vigia Trujillo (8°35’54"N, 71°37’31"W), MCNG 32199, 1 (72). Trujillo: río Monay, Maracaibo basin (9°34’N, 70°36’W), INHS 28812, 1 (113). Río Motatán, 4 km above Motatán (9°24’N, 70°36’W), USNM 121265, 1 (142, holotype of Pseudocetopsis plumbeus motatanensis ). Río San Juan, tributary of río Motatán, at bridge, USNM 121266, 1 (57.5, paratype of Pseudocetopsis plumbeus motatanensis ). Río Motatán, 8 km below Motatán (approximately 9°22’N, 70°34’W), USNM 121267, 2 (67-81, paratypes of Pseudocetopsis plumbeus motatanensis ). Río Motatán, 4 km below Motatán (approximately 9°24’N, 70°36’W), USNM 121268, 2 (109-155, paratypes of Pseudocetopsis plumbeus motatanensis ). Río Motatán, at bridge, 22 km N of Motatán (approximately 9°26’N, 70°35’W), USNM 121269, 3 (59-83, paraty-pes of Pseudocetopsis plumbeus motatanensis , largest specimen a mature male, 1 specimen, 77 mm, cleared and stained).

Cetopsis oliveirai (Lundberg & Rapp Py-Daniel, 1994) Figs. 25 , 29 , Tables 9 -15

Bathycetopsis oliveirai Lundberg & Rapp Py-Daniel, 1994: 383 , fig. 3 [type locality: Brazil, Amazonas State , rio Solimões north of Ilha da Marchantaria , approximately 15 km upstream of the mouth of rio Negro at Manaus, 3°15’S, 60°00’W].– de Pinna & Vari, 1995: 9 [phylogenetic position].– Evers & Seidel, 2002: 741 [listing].– Vari & Ferraris, 2003: 257 [in check list; distribution].

Diagnosis. Cetopsis oliveirai can be readily distinguished from all other members of the Cetopsinae by its complete absence of eyes (versus the presence of those organs to some degree in all other species of the Cetopsinae ) and the presence of extremely-elongate distal filaments on the first ray of the dorsal fin (length of fin longer than one-half of the SL) and pectoral fin (filament extending posteriorly to beyond the vertical through the middle of the base of the anal fin). It is further distinguished among the species of Cetopsis by the number of total anal-fin rays (17 to 19 versus 22 or above in all congeners) and caudal vertebrae (25 or 26 versus 28 or above, respectively).

Description. Body relatively slender, somewhat compressed anteriorly, becoming increasingly compressed posteriorly. Body depth at dorsal-fin origin approximately 0.20-0.21 of SL and approximately two-thirds of HL. Lateral line on body complete, unbranched, and midlateral; extending from vertical through pectoral-fin base onto hypural plate and terminating slightly prior to, or at, posterior margin of hypural plate. Dorsal profile of body variably slightly convex from nape to dorsal-fin origin; straight to slightly convex from dorsal-fin origin to caudal-fin base. Ventral profile of body nearly straight along abdomen, approximately straight or slightly concave, but posterodorsally slanted, along base of anal fin. Caudalpeduncle depth approximately equal to two-thirds of caudalpeduncle length.

Head triangular overall in profile and tapers to acute, rounded tip anteriorly. Dorsal profile of head convex from tip of snout to posterior of nape. Ventral profile of head slightly less convex than dorsal profile. Profile of snout in dorsal view converging to level of anterior nares, then incised between anterior nares and tip of snout, with anterior margin of snout rounded (see Lundberg and Rapp Py-Daniel, 1994, fig. 4). Lateral margins of portion of head posterior of posterior nares running approximately in parallel. Dorsal surface of posterior portion of head without externally-apparent, enlarged jaw musculature.

Opercular membrane attaching to isthmus as far posteriorly as vertical through pectoral-fin insertion. Opercular opening relatively restricted; extending approximately equal distances both dorsal and ventral of pectoral-fin insertion; overall length of aperture approximately equal to distance from tip of snout to symphysis of lower jaw.

Eye absent. Anterior narial opening circular, surrounded by short, anteriorly-directed tubular rim of skin. Opening of anterior nares located at horizontal extending through both tip of snout and maxillary-barbel origin. Distance between anterior nares approximately equal to one-half of distance from anterior to posterior nares. Posterior narial opening located on dorsal surface of head proximate to dorsal profile of head; opening ovoid, with long axis of aperture running in parallel to body axis. Distance between posterior nares approximately one-half distance between anterior nares. Anterior one-half of posterior narial opening bordered by low flap of skin.

Mouth inferior; its width approximately one-fourth to onethird of HL. Margin of lower jaw broadly rounded, its posterior limit falling just short of vertical through anterior margin of posterior nares. Premaxillary tooth patch elongate, continuous across premaxillae with anterior margin convex and posterior margin concave and running in parallel to anterior margin. Teeth on upper jaw small, conical, and sharplypointed; with teeth arrayed in two rows for most of length of premaxilla, but reduced to one row near symphysis. All premaxillary teeth of approximately same size. Vomerine teeth arranged in single, anteriorly-convex, continuous row. Vomerine teeth stout, conical, sharply-pointed, of uniform size throughout, and much larger than teeth in either jaw. Dentary with single row of conical, pointed teeth along much of dentigerous surface and with shorter second tooth row located anterior to primary tooth row in region proximate to symphysis. Primary row of teeth of uniform size throughout and slightly shorter than, but distinctly less stout than, those on vomer. Teeth of anterior dentary tooth row slightly smaller than those in primary tooth row.

Maxillary barbel slender, its length slightly greater than HL; barbel origin located at horizontal extending through anterior nares and midway between verticals through anterior and posterior nares. Length of mental barbels approximately two-thirds of HL. Medial mental-barbel origin located slightly anterior to vertical through posterior nares. Lateral mental-barbel origin situated along vertical through posterior margin of posterior nares. Tips of adpressed mental barbels extending past pectoral-fin insertion.

Dorsal fin with first ray distinctly elongate, its length greater than 0.50 of SL. No sexual dimorphism apparent in length of first dorsal-fin ray. Length of base of dorsal fin slightly less than one-half of HL, its length approximately equal to distance between anterior and posterior nares. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous. Distal margin of dorsal fin nearly straight from second to sixth rays and convex from sixth to posterior most fin ray. Dorsal-fin origin located at approximately anterior one-third of SL, and along vertical through distal one-third of adpressed pectoral fin excluding distal filament on first ray. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal fin moderately-forked, symmetrical or nearly symmetrical; tips of lobes in form of rounded point. Length of longest caudal-fin ray slightly less that two times length of middle fin rays.

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

Pelvic fin short; distal margin nearly straight with first ray longest. Pelvic-fin insertion located approximately at middle of SL and entirely posterior to vertical through posterior terminus of base of dorsal fin. Tip of adpressed pelvic fin falling short of vertical through vent. Medial most pelvic-fin ray with membranous attachment to body for basal two-thirds of its length.

Pectoral fin with long, filamentous, non-spinous first ray, with tip of ray extending to beyond vertical through middle of base of anal fin. No sexual dimorphism apparent in degree of development of filament. Pectoral-fin margin straight and obliquely-angled medial to filamentous ray.

Coloration in alcohol. Few, small, scattered, dark chromatophores present in some specimens on occipital region of head and on either side of dorsal midline of body in region from nape to vertical through posterior portion of base of anal fin. Rest of head, body, and fins without dark pigmentation. Remaining examined specimens lacking any dark pigmentation on head, body, fins, and barbels.

Coloration in life. Based on photograph of recently captured specimen from southeastern Peru provided by M. Goulding. Overall coloration of head and body pink. Midlateral surface of caudal peduncle and lateral, but not dorsolateral, surface of body bright silver. No dark pigmentation apparent on head, body, or fins.

Sexual dimorphism. Cetopsis oliveirai does not demonstrate the sexual dimorphism in the degree of development of the dramatically-developed filaments on the dorsal and pectoral fins and in the form of the margin of anal-fin that is present in many other species of the Cetopsinae .

Ecology. All examined specimens of Cetopsis oliveirai were captured using trawl-nets in the main channels of large rivers in the Amazon basin. Lundberg & Rapp Py-Daniel (1994) reported that all of their specimens of the species originated in white water systems at depths of 2 to 40 m and that the species feeds on terrestrial arthropods. Peruvian samples were captured at depth of approximately 20 m in the middle of the main river channel (F. Chang, MUSM; pers. commun., 1996).

Distribution. Cetopsis oliveirai is known from the middle and upper portions of the Amazon basin in Brazil and Peru ( Fig. 25 ). Given that C. oliveirai inhabits a difficult to sample habitat, the middle and bottom portions of the water column of main river channels, it is likely that the actual geographic distribution of the species is distinctly greater than is indicated by the available population samples.

Material examined. 46 specimens (40, 15- 36 mm SL). Brazil. Amazonas: rio Solimões , 5.4 km below Paraná de Javarimim, MZUSP 79338 , 2 (30.5-32.0; 1 specimen, 33 mm, cleared and stained) . Rio Solimões , 17.8 km below Lago Amori, MZUSP 79337 , 3 (23-28; 1 specimen, 28 mm, cleared and stained) . Rio Solimões, near Ilha de Marchantaria and Ilha Baixo , approximately 10 to 20 km above rio Negro (approximately 3°10’S, 59°44’W), MZUSP 44068 , 1 (27, paratype of Bathycetopsis oliveirai ) . Rio Solimões, near Ilha de Marchantaria and Ilha Baixo , approximately 10 km above rio Negro (approximately 3°10’S, 59°44’W), DU F1170 , 1 (30) . Rio Solimões, 13 km downstream of São Antonio do Iça (approximately 3°05’S, 67°57’W), USNM 352353 , 3 (26-29) . Rio Solimões (approximately 3°18’24"S, 67°57’17"W), USNM 371875 , 5 (15-33) . Rio Solimões (approximately 3°20’29.2"S, 67°59’26"W), USNM 371876 , 1 (32) . Rio Solimões, 1.9 km from its mouth upriver to Japurá (3°13’21"S, 64°46’58"W), MZUSP 56430 , 2 (29-30) . Rio Solimões, 26.2 km above Paraná Porto Alegre (2°40’49"S, 66°53’21"W), MZUSP 56428 , 3 (20-26) . Rio Solimões, below Purus (3°35’49"S, 61°20’56"W), MZUSP 57758 , 1 (30) . Rio Solimões , 50 km below Paraná do Jucaram (2°53’11"S, 65°11’01"W), MZUSP 56299 , 1 (29) . Rio Solimões , 25 km below Paraná Amaturá (3°10’48"S, 67°55’40"W), MZUSP 55683 , 1 (29) . Rio Içá, 13.9 km below paraná Pombas (3°06’55"S, 68°04’W), MZUSP 56429 , 1 (21) ; MZUSP 79336 , 1 (21) . Rio Amazonas (3°17’33"S, 58°54’13"), MZUSP 57762 , 1 (29) . Rio Amazonas, above mouth of rio Madeira (approximately 3°17’27"S, 58°56’33"W), USNM 371878 , 1 (27.9) . Rio Amazonas, above mouth of rio Madeira (approximately 3°16’28.7"S, 58°55’31"W), USNM 371877 , 1 (28.0) . Para: rio Amazonas, 36.9 km below Tapajós (2°25’27"S, 54°24’30"W), MZUSP 55693 , 1 (29) . Peru. Loreto: río Aguarico, at Castana (0°48’S, 75°14’W), MUSM 4849 , 6 (33-36) . Madre de Dios: Palma Real (12°36’S 68°57’W), MUSM 9033 , 10 (22-35).

Figures

Fig. 25. Map of central and northern South America showing geographic distribution of Cetopsis jurubidae (1 = holotype locality ofPseudocetopsisjurubidae), Cetopsis montana (2= holotype locality), Cetopsis motatanensis (3 = holotype locality of Pseudocetopsis plumbeus motatanensis), and Cetopsis oliveirai (4 = holotype locality of Bathycetopsis oliveirai) (some symbols represent more that one locality and/or lot of specimens).

Fig. 27. Cetopsis motatanensis, paratype of Pseudocetopsis plumbeus motatanensis, male (right side, reversed), USNM 121268, 109 mm SL; Venezuela, Trujillo, río Motatán, 4 km below Motatán (approximately 9°24’N, 70°36’W).

Fig. 28. Cetopsis motatanensis, paratype of Pseudocetopsis plumbeus motatanensis, female, USNM 121268, 155 mm SL; Venezuela, Trujillo, río Motatán, 4 km below Motatán (approximately 9°24’N, 70°36’W).

Fig. 17. Cetopsis candiru, mature male, FMNH 112635, 194 mm SL; Peru, Loreto, río Pastaza basin, caño tributary to laguna Rimachi, near río Rimachi, at Rimachi(4°26.91’S, 76°39.48’W).

Fig. 29. Cetopsis oliveirai, MUSM 9033, 30.6 mm SL; Peru, Madre de Dios, Palma Real (12°36’S 68°57’W).