Cetopsidium roae, 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 : 147-150

Cetopsidium roae , new species

Figs. 2 , 10 , Tables 2-8

Diagnosis. Cetopsidium roae differs from all of its congeners in the position of the vent (distinctly separated from the base of the anterior most anal-fin ray versus proximate to the base of the anterior most anal-fin ray, respectively). Cetopsidium roae further differs from C. ferreirai in the alignment of the dorsal and ventral profiles of the portion of the body posterior of the base of the dorsal fin (running in parallel versus converging, respectively). Cetopsidium roae differs from C. minutum in the length of the pelvic fin (tip of the adpressed fin distinctly separated from the base of the anterior most anal-fin ray versus proximate to the base of the anterior most anal-fin ray, respectively) and in the length of the pectoral fin (tip of fin falling distinctly short of the vertical through the pelvic-fin insertion versus reaching that line, respectively). Cetopsidium roae also differs from C. morenoi in the alignment of the dorsal and ventral profiles of the portion of the body posterior of the base of the dorsal fin (running in parallel versus converging posteriorly, respectively) and in the form of the dark pigmentation on the body (small, point-like, scattered chromatophores on the dorsal and lateral surfaces of head versus large stellate chromatophores in that region, respectively). Cetopsidium roae further differs from C. orientale in the overall coloration (small, point-like, scattered chromatophores distributed over the dorsal and lateral surfaces of head and body versus large, stellate, dark chromatophores densely covering the dorsal and lateral surfaces of the head and body, respectively). Cetopsidium roae also differs from C. pemon in the alignment of the dorsal and ventral profiles of the portion of the body posterior of the base of the dorsal fin (running in parallel versus converging posteriorly, respectively) and in the prolongations of the distal portions of the first rays of the dorsal and pectoral fins in mature males as indicated by the presence of a distinctly convex margin to the anal fin (prolongations apparently absent versus present, respectively).

Description. Body elongate, nearly cylindrical anteriorly and becoming progressively distinctly-compressed posteriorly. Body depth at dorsal-fin origin approximately 0.14-0.15 of SL and approximately equal to postorbital length of head. Lateral line on body incomplete, unbranched, and midlateral; extending from vertical through pectoral-fin base posteriorly at least to region dorsal of base of anal fin, and in some individuals reaching vertical through anterior limit of caudal peduncle. Dorsal profile of body straight from nape to dorsalfin origin and straight from dorsal-fin origin to caudal-fin base. Ventral profile of body very slightly convex along abdomen, approximately straight, with base of anal fin straight and running nearly in parallel to horizontal axis of body. Caudal-peduncle depth slightly less than caudal-peduncle length.

Head in profile acutely triangular overall with bluntlypointed snout. Dorsal profile of head nearly straight from tip of snout to vertical through posterior margin of orbit and broadly convex from that point to nape. Ventral profile of head slightly convex. Margin of snout in dorsal view broadly rounded. Postorbital margins of head slightly convex on each side from dorsal view. Enlarged jaw musculature very evident externally on dorsal and lateral surfaces of postorbital portion of head.

Opercular membrane attaching to isthmus only anterior of vertical through pectoral-fin insertion. Opercular opening moderately-elongate; extending anteroventral of pectoral-fin insertion by distance approximately equal to one-third of HL and extending dorsal of pectoral-fin insertion by distance equal to width of eye.

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 0.40 of HL. 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 slightly dorsal of horizontal extending through maxillary-barbel origin and at, or slightly ventral of, horizontal running through tip of snout. Distance between anterior nares approximately equal to distance from tip of snout to anterior margin of orbit. Posterior narial opening located on dorsal surface of head, situated dorsal to anterior one-third of orbit; narial opening nearly round and with flap of skin extending along anterior twothirds of rim of aperture and flap highest anteromedially.

Mouth subterminal; its width approximately 0.50 of HL. Margin of lower jaw gently rounded, its posterior limit reaching to vertical through middle 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, sharply-pointed, and arranged in three more or less regular rows of uniform-sized teeth across premaxilla. Vomerine teeth arranged in single, arched row with distinct gap in tooth series at midline. Vomerine teeth stout, conical, of approximately uniform size, and stouter but not distinctly longer than teeth on premaxilla. Dentary teeth comparable in shape and size to premaxillary teeth. Dentary dentition consisting of three irregular rows medially that taper to one row laterally.

Maxillary barbel slender, its length approximately equal to distance from anterior margin of orbit to posterior margin of opercle, and slightly greater than three-fourths of HL; barbel origin located ventral to anterior margin of orbit. Medial mental barbel approximately equal in length to lateral mental barbel, and shorter than maxillary barbel. Medial mental-barbel origin located along vertical through rictus. Lateral mentalbarbel origin situated slightly posterior of vertical through medial mental-barbel origin. Tips of adpressed mental barbels extending to, or slightly past, posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.41-0.43 of HL. Length of longest branched dorsal-fin ray equal to slightly more than two-thirds of HL. Dorsal-fin spinelet present, first dorsal-fin ray spinous for basal one-half of its length, flexible more distally, and not prolonged beyond fin margin as distal filament. Distal margin of dorsal fin slightly convex, with first branched ray longest. Dorsal-fin origin located at approximately anterior 0.30 of SL and along vertical extending through posterior one-fourth to one-third of adpressed pectoral fin. Tip of adpressed dorsal fin falling slightly short of vertical through vent. Posterior most dorsal-fin ray with short posterior, membranous attachment to body basally.

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

Preanal Vertebrae

1314151617 C. ferreirai 1 1 1 1

C. minutum 1 1

C. morenoi 2 18 23 5

C. orientale 1 11 20 6 1

C. pemon 1 6 10 12

C. roae 9 8 2

Precaudal Vertebrae

1011121314 C. ferreirai 1 - 2 1 C. minutum 2

C. morenoi 14 10 20 6

C. orientale 1 23 16 4

C. pemon 2 5 16 6 2

C. roae 2 11 4 2

Base of anal fin moderately long. Anal-fin origin located distinctly posterior of middle of SL and anterior of middle of TL. Anal-fin margin nearly straight or slightly convex in all examined specimens. Posterior most anal-fin ray with slight, membranous attachment to body.

Pelvic fin proportionally small; distal margin slightly convex, with middle fin rays 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 and vent, but falling far short of anterior limit of base of anal fin. Medial most pelvic-fin ray with membranous attachment to body along basal one-half of its length.

Pectoral-fin length approximately two-thirds of HL. Pectoral-fin margin distinctly convex with middle ray longest. First pectoral-fin ray spinous with smooth margins. Spine short with length slightly more than one-half that of first branched ray; ray not prolonged beyond fin margin as filament.

Coloration in alcohol. Overall ground coloration of head and body pale and overlain with rounded, brown chromatophores. Dark pigmentation on head and body tends to be more concentrated dorsally but never forming intensely dark pigmentation. Ventral surface of abdomen and head pale.

Dorsal and anal fins pale, with scattered, dark chromatophores basally. Caudal fin with widely scattered, tiny, dark chromatophores on fleshy basal part of fin and with rayed part of fin pale. Pelvic and pectoral fins pale.

All barbels pale.

Sexual dimorphism. No sexual dimorphism was apparent in the available population samples of Cetopsidium roae .

Distribution. Cetopsidium roae is only known from the Rupununi region of southwestern Guyana ( Fig. 2 ).

Etymology. The species name, roae , is in honor of the collector of all the known specimens of the species, Rosemary Lowe- McConnell, known as Ro to her many colleagues and friends, in recognition of her contributions to our knowledge of the fishes of Guyana and many other regions of the world.

Material examined. 20 specimens (21-41 mm SL). Holotype. Guyana. Rupununi River , Karanambo (3°45’N, 58°18’W), R . H. Lowe-McConnell, BMNH 1972.7 .27.629, 1 (34). Paratypes. 19 specimens (21-41 mm SL). Guyana. Rupununi River , Karanambo (3°45’N, 58°18’W), collected with holotype, BMNH 1972.7.27.630-642, 12 (21-34). Rupununi (exact locality unspecified), R . H. Lowe-McConnell, BMNH 1985.6.21.39-42, 4 (30-41).

Figures

Fig. 2. Map of central and northern South America showing geographic distribution of Cetopsidium ferreirai (1 = holotype locality), Cetopsidium minutum (2 = holotype locality of Hemicetopsis minutus), Cetopsidium morenoi, Cetopsidium orientale (3 = holotype locality of Pseudocetopsis orientale), Cetopsidium pemon (4 = holotype locality), and Cetopsidium roae (5 = holotype locality) (some symbols represent more that one locality and/or lot of specimens).

Fig. 10. Cetopsidium roae, new species, holotype, BMNH 1972.7.27:629-642, 34 mm SL; Guyana, Rupununi River, Karanambo (3°45’N, 58°18’W).