Cetopsis umbrosa, 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 : 201-205

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

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scientific name

Cetopsis umbrosa

new species

Cetopsis umbrosa , new species

Figs. 41 View Fig , 44 View Fig , Tables 9 -15

Diagnosis. Cetopsis umbrosa 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 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 and 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 presence of fine, scattered, dark pigmentation across the lateral and anterior surfaces of snout and the lateral surface of the body. It is further distinguished from the externally somewhat similar C. starnesi in the number of precaudal vertebrae (14 versus 11 or 12, respectively), caudal vertebrae (30 versus 33, respectively), and total anal-fin rays (26 versus 27 or 28, respectively).

Description. Body moderately-elongate, slightly-compressed anteriorly and becoming progressively distinctly-compressed posteriorly. Body depth at dorsal-fin origin approximately 0.22 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, and extending from vertical through pectoral-fin base to hypural plate with short, dorsal bend on hypural plate. Dorsal profile of body nearly straight from nape to dorsal-fin origin and 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. Caudalpeduncle depth slightly greater than caudal-peduncle length.

Head in profile acutely triangular overall. Dorsal profile of head nearly straight from tip of snout to nape. Ventral profile of head slightly convex. Margin of snout in dorsal view distinctly triangular. Postorbital margins of head running nearly in parallel from dorsal view. Enlarged jaw musculature not evident externally on dorsal surface of postorbital portion of head.

Opercular membrane attaching to isthmus only anterior of vertical through pectoral-fin insertion. Opercular opening moderate; extending ventral of pectoral-fin insertion by distance equal to snout length and extending dorsal of pectoralfin 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 at approximately anterior one-third of HL. Eye diameter approximately one-half of snout length. Interorbital width approximately equal to snout length. 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, but ventral of horizontal running through tip of snout. 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 and with anterior two-thirds surrounded by flap of skin, flap highest anteriorly.

Mouth inferior; its width approximately one-half of HL. Margin of lower jaw 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. Teeth of inner most row of premaxillary dentition slightly larger than the teeth in other tooth rows. Vomerine teeth arranged in single, irregular row continuous across midline. Vomerine teeth stout, conical, and much larger than teeth on premaxilla or dentary. Dentary teeth comparable in shape to, but larger in size than, premaxillary teeth. Dentary dentition consisting of two regular rows. Teeth of inner tooth row large than those of outer row. Outer tooth row beginning at symphysis, but not extending as far laterally as inner tooth row..

Maxillary barbel slender, its length greater than distance from tip of snout to posterior margins of orbit, but slightly greater 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 medial mental-barbel origin. Tips of adpressed mental barbels extending to, or slightly beyond, posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.40-0.43 of HL. Length of longest branched dorsal-fin ray, excluding distal filament, approximately equal to three-fourths of HL. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous but with distal filament present in single available specimen. Distal margin of dorsal fin nearly straight, with first ray longest. Dorsal-fin origin located at approximately anterior 0.36 of SL and along vertical extending through distal one-fourth of adpressed pectoral fin. Tip of longest branched ray of adpressed dorsal fin, excluding distal filament on first ray, reaching nearly to vertical through vent. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal fin forked, apparently symmetrical; tips of lobes damaged in single available specimen.

Base of anal fin moderately long. Anal-fin origin located well posterior of middle of SL, and approximately along vertical through middle of TL. Anal-fin margin slightly convex in single available specimen, an apparently mature male. 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 portion of base of dorsal fin. Tip of adpressed pelvic fin extending beyond middle of SL and falling 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. First pectoral-fin ray not spinous, but with first ray longest and prolonged into distal filament. Pectoral-fin margin sinusoidal, concave laterally and convex medially.

Coloration in alcohol. Scattered, dark pigmentation covering dorsal portion of head from tip of snout to rear of head. Interorbital region slightly darker than adjoining areas. Areas posteroventral and posterior of orbit with patch of distinct, large, dark chromatophores. Opercular region and ventral portions of head lack distinct, dark chromatophores. Dorsal portion of body dark. Lateral surface of body with scattered, very small, superficial, dark chromatophores and with scattered, deep-lying, dark spots smaller than size of pupil. Spots rarely coalesce into larger spots other than on posterior portion of caudal peduncle. Caudal peduncle with numerous dark spots. Ventral and ventrolateral surface of abdomen pale.

Dorsal fin pale, with some indication of dusky basal region; fin membranes otherwise hyaline. Caudal fin largely pale but with dark, bilobed spot extending from base of branched fin-rays posteriorly approximately to vertical through middle of length of inner most rays. Anal fin pale other than for some scattered, dark, superficial chromatophores on basal portion of fin. Pectoral and pelvic fins pale.

Barbels dusky on basal portion of anterior surface but otherwise pale.

Sexual dimorphism. The holotype, the only available specimen of Cetopsis umbrosa , is presumed to be a mature male in light of its possession of distal filaments on the first rays of the dorsal and pectoral fins and the presence of a convex margin of the anal fin. These features are typical of mature males of many other species in the Cetopsinae .

Distribution. Cetopsis umbrosa is known only from a single locality in the western portions of the río Orinoco basin ( Fig. 41 View Fig ).

Remarks. Although Cetopsis umbrosa is known from only one specimen, the combination of characters noted in the “Diagnosis” serves to distinguish if from all congeners. It is most similar overall to C. starnesi , a species that also has a bilobed dark spot at the base of the caudal fin, but whose distributional range in southern Bolivia is geographically distant from the location within Colombia where the holotype of

Preanal vertebrae

141516171819202122232425 C . amphiloxa 3 1 3

C. arcana 1 7 2

C. baudoensis 5 7 2

C. caiapo 1

C. candiru 3 6 21 5 4 C. coecutiens 1 19 50 23 3 1 C. fimbriata 1 1 4 11 2

C. gobioides 12 15 6

C. jurubidae 1

C. montana 7 10

C. motatanensis 2 5 1

C. oliveirai 6 6 2

C. orinoco 3 24 28 5 2

C. othonops 1 11 18 6

C. parma 1 - 1 - 1

C. pearsoni 2 4 1

C. plumbea 8 12 17 11 3

C. sandrae 1 2 2 1

C. sarcodes 1

C. starnesi 1 1

C. umbrosa 1

C. umbrosa was collected. Furthermore, those two species differ in a number of features, most notably in the number of precaudal and caudal vertebrae (see Tables 13, 14). Additional specimens of each species are necessary to determine whether the apparent difference in the number of total analfin rays in the two species ( Table 11) also serves to distinguish the two nominal forms.

One specimen from a locality rather distant from the known distribution of Cetopsis umbrosa (INPA 8485) either represents this species or a closely related, albeit perhaps undescribed, form (see comments under “Remarks” for C. montana ).

holotype value for Etymology. The specific name, umbrosa , from the Latin for shady refers to the presence of pigmentation on the dorsal and anterior portions of the snout. This pigmentation pattern contrasts with the unpigmented snout characteristic of the geographically-proximate and somewhat externally similar C. montana .

Material examined. 1 specimen (54 mm SL). Holotype. Colombia. Meta: río Negro, downstream from main Villavicencio to Puerto Lopez highway at La Balsa (04°04’N, 73°04’W), J. E. Böhlke et al., 29 February 1972, ANSP 137559 View Materials , 1 View Materials (54). GoogleMaps