Cetopsis sandrae, 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 : 195-197

Cetopsis sandrae , new species

Figs. 39-41 , Tables 9 -15

Diagnosis. Cetopsis sandrae 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 presence of a spot of dark pigmentation on the base of the dorsal fin with prominent dark pigmentation present along the membrane behind the first ray of the dorsal fin, the possession of 40 or 41 total vertebrae (with 40 most common), the lack of a distinct demarcation between the dark pigmentation on the dorsal and dorsolateral surfaces of the body versus more ventral regions, and the presence of eye size or larger, dark spots on the ventral and ventrolateral surfaces of the body in the region below the horizontal extending through the ventral margin of the caudal peduncle.

Description. Body moderately stout, slightly-compressed laterally anteriorly and becoming progressively distinctlycompressed posteriorly. Body depth at dorsal-fin origin approximately 0.29-0.30 of SL, and slightly greater than 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 from nape to dorsal-fin origin and nearly 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 greater than caudal-peduncle length.

Head in profile acutely triangular overall with bluntlyrounded snout. Dorsal profile of head slightly convex from tip of snout to nape. Ventral profile of head slightly convex. Margin of snout in dorsal view bluntly triangular. Postorbital margins of head aligned nearly in parallel from dorsal view. Enlarged jaw musculature apparent 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 distance from tip of snout to middle of eye and extending dorsal of pectoral-fin insertion by distance approximately 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 0.30 of HL. Eye diameter approximately one-half 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 along horizontal extending through maxillary-barbel origin and ventral of horizontal extending 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, with anterior two-thirds of aperture 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 and with anterior margin convex and posterior margin concave and running in parallel to anterior margin. Teeth on premaxilla small, conical, sharply-pointed, uniform-sized, and arranged in three regular rows. Vomerine teeth arranged in single irregular row apparently continuous across midline. Vomerine teeth stout, conical, and much larger than teeth on premaxilla and approximately as large as largest teeth on dentary. Dentary teeth comparable in shape to, but larger in size than, premaxillary teeth. Dentary dentition consisting of two or three irregular rows medially that taper to one row laterally.

Maxillary barbel slender, its length approximately equal to distance from tip of snout to posterior margin of eye, and nearly one-half of HL; barbel origin located ventral to middle of orbit. Medial mental barbels approximately same length as lateral mental barbels and slightly shorter than maxillary barbels. 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 falling just short of posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.40-0.41 of HL. Longest branched dorsal-fin ray, excluding distal filament on first ray, equal in length to two-thirds of HL. Dorsal-fin spinelet absent. First dorsal-fin ray not spinous but with at least short, distal filament in all specimens, and with filament proportionally longer in apparently mature males ( Fig. 39 ). Distal margin of dorsal fin slightly sinusoidal with anterior portion concave and posterior portion convex. Dorsal-fin origin located at approximately anterior 0.36-0.37 of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin, excluding filament, nearly reaching to vertical through vent. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal fin moderately-forked, symmetrical; tips of lobes rounded. Length of longest caudal-fin ray approximately 1.75 times length of middle fin rays.

Base of anal fin moderately long. Anal-fin origin located distinctly posterior of middle of SL and nearly at middle of TL.Anal-fin margin straight in females ( Fig. 40 ) and immature males, with posterior most unbranched anal-fin ray longest and with subsequent rays becoming gradually shorter. Analfin margin convex in mature males ( Fig. 39 ) and in apparently maturing male of 45 mm SL that does not demonstrate other sexually-dimorphic male characteristics of dorsal and pectoral fins. Posterior most anal-fin ray without posterior, membranous attachment to body.

Pelvic fin moderately long; distal margin distinctly convex, with first 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 past middle of SL, but falling short of anterior margin of vent. Medial most pelvic-fin ray with membranous attachment to body along basal two-thirds of its length.

Pectoral-fin length approximately 0.60 of HL. Pectoral-fin margin slightly convex, with first ray longest and prolonged into filament, filament proportionally longer in mature males. First pectoral-fin ray not spinous.

sandrae also have the anal-fin margin distinctly convex rather than straight as occurs in females and immature males of that species.

Ecology. The holotype of Cetopsis sandrae and the paratypes of the species collected with it were collected in a relatively fast-flowing forest stream, approximately 3-4 m wide and 0.4- 0.8 m deep with a small waterfall. All the samples were collected in riffles along the stream (F.C. T. Lima, MZUSP; pers. commun., 2003) .

Distribution. Cetopsis sandrae is known only from the rio Arinos in the upper portions of the rio Tapajós system, Amazon basin ( Fig. 41 )

Coloration in alcohol. Dark pigmentation covering dorsal portion of head from tip of snout to posterior margin of head. Dark, dorsal pigmentation continuous with dark region posterodorsal and posterior to orbit. Remaining portions of head pale. Dorsal portion of body dark. Lateral surface of body irregularly covered with fine, dark spots; spots often coalesce into eye-size blotches, with such coalescence more prevalent ventral of lateral line. Heavily pigmented individuals with lateral surface of body nearly uniformly dark. Ventral surface of body pale, with few, scattered, dark spots present only in most heavily pigmented individuals.

Dorsal fin irregularly covered with dark pigmentation; pigmentation more concentrated basally and forming semicircular dark spot above base of fin. Anterior margin and distal portions of dorsal fin pale, but with dark pigmentation along first interradial membrane. Caudal-fin rays outlined by scattered, dark pigmentation except for narrow, clear band along distal margin of fin. Anal fin with scattered, dark pigmentation along base and with dark pigmentation rarely extending varying distances onto main body of fin. Pectoral fin pale other than for occasional dark pigment spots on basal or distal portions of first fin ray. Pelvic fin pale.

Maxillary and mental barbel dusky basally and with distal portion pale.

Sexual dimorphism. Mature males of Cetopsis sandrae have the filaments on the first rays of the dorsal and pectoral fins proportionally more elongate than are the extensions on those ray in conspecific females and immature males. Males of C. Etymology. The specific name, sandrae , is in reference to Sandra J. Raredon, of the Division of Fishes, National Museum of Natural History, in thanks for all of her assistance to the authors, particularly the first author, over the course of the years in this and many other projects.

Material examined. 6 specimens (6, 45-75 mm SL). Holotype. Brazil. Mato Grosso: Nova Mutum, unnamed córrego, Fazenda Buriti, approximately 1.5 km S of Fazenda (13°51’52"S, 56°11’36"W), MZUSP Ichthyology students, 16 February 2000, MZUSP 61091 , 1 , mature male (64) . Paratypes. 5 specimens (5, 45-75 mm SL). Brazil. Mato Grosso: Nova Mutum, unnamed córrego, Fazenda Buriti, approximately 1.5 km S of Fazenda, collected with holotype, MZUSP 83227 , 3 (45-75); USNM 372766 , 1 (63). Nova Mutum , riacho tributary to rio Arinos , Fazenda Buriti , MZUSP Ichthyology students, 20 Feb 2000, MZUSP 61051 , 1 (46, cleared and stained) .

Figures

Fig. 39. Cetopsis sandrae, new species, holotype, male, MZUSP 61091, 64 mm SL; Brazil, Mato Grosso, Nova Mutum, unnamed Córrego, Fazenda Buriti (13°51’52"S, 56°11’36"W).

Fig. 40. Cetopsis sandrae, new species, paratype, female, MZUSP 83227, 75 mm SL; Brazil, Mato Grosso, Nova Mutum, unnamed Córrego, Fazenda Buriti (13°51’52"S, 56°11’36"W).

Fig. 41. Map of central and northern SouthAmerica showing geographic distribution of Cetopsis sandrae (1 = holotype locality), Cetopsis sarcodes (2 = holotype locality), Cetopsis starnesi (3 = holotype locality), and Cetopsis umbrosa (4 = holotype locality) (some symbols represent more that one locality and/or lot of specimens).