Cetopsidium ferreirai, 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 : 133-136

Cetopsidium ferreirai , new species

Figs. 1-2 , Tables 2-8

Pseudocetopsis minuta [not of Eigenmann, 1912].– Ferreira, 1995: 52, table 3 [ Brazil: Pará, rio Trombetas basin].

Diagnosis. Cetopsidium ferreirai differs from all of its congeners with the possible exception of C. roae and C. minutum (see those species accounts) in the lack of distal filaments on the first rays of the dorsal and pectoral fins in adult males (versus the presence of such filaments in adult males as indicated by the possession of distinctly convex anal-fin margins, respectively). Cetopsidium ferreirai further differs from C. minutum in the length of the pelvic fin (falling short of anal-fin origin versus extending at least to anal-fin origin, respectively). Cetopsidium ferreirai further differs from C. morenoi in the overall form of the head (the head being not massive proportionally as a consequence of the less extensive development of the adductor mandibulae muscle onto the dorsal surface of head and with the snout distinctly rounded versus the head being proportionally massive with well-developed, distinctly bulging adductor mandibulae muscles and the snout less rounded, respectively; compare Fig. 1 with Figs. 5 , 6 ), and the less extensive dark pigmentation on the body (the near absence of dark pigmentation on the lateral surface of body and the pigmentation limited to the middorsal region of body versus the dark pigmentation being distributed over much of the lateral and dorsal surfaces of the body, respectively). Cetopsidium ferreirai further differs from C. orientale in the alignment of the dorsal and ventral profiles of the portion of the body posterior of the base of the dorsal fin (profiles converging posteriorly versus running in parallel, respectively) and in the overall coloration (limited dark pigmentation located largely along the middorsal region of the body versus dark pigmentation widely distributed over the dorsal and lateral portions of body, respectively). Cetopsidium ferreirai further differs from C. pemon in the overall form of the head (profile of head anteriorly rounded versus distinctly pointed, respectively) and in the proportional length of the snout (approximately 2 times diameter of the eye versus approximately 3 times diameter of the eye, respectively). Cetopsidium ferreirai further differs from C. roae in the position of the vent (proximate to the base of the anterior most anal-fin ray versus distinctly separated from the base of the anterior most anal-fin ray, respectively).

Description. Body elongate, barely compressed laterally anteriorly and becoming progressively distinctly-compressed posteriorly. Body depth at dorsal-fin origin approximately 0.18- 0.20 of SL, and slightly less than HL. Lateral line on body incomplete, unbranched, and midlateral; extending posteriorly to over posterior portion of base of anal fin but falling short of caudal peduncle. 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 slightly convex along abdomen, approximately straight, and nearly running in parallel to dorsal profile along region of caudal peduncle. Caudal-peduncle depth approximately equal to caudal-peduncle length.

Head in profile acutely triangular overall with bluntlypointed snout. Dorsal profile of head convex from tip of snout to vertical through posterior margin of orbit and nearly straight from that point to nape. Ventral profile of head slightly convex. Margin of snout rounded from dorsal view. Lateral margins of postorbital portion 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 diameter of eye.

Eye situated on lateral surface of head; located entirely dorsal to horizontal 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 slightly more than one-half of snout length. Interorbital width approximately equal to distance from tip of snout to middle 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 extending through tip of snout. Distance between anterior nares approximately equal to distance from tip of snout to posterior 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 one-half of rim of aperture, with flap highest anteriorly.

Mouth subterminal, its width approximately two-fifths 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 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 two, more or less regular, rows of uniform-sized teeth medially and reduced to one row at lateral limit of premaxilla. Vomerine teeth arranged in single, arched row with distinct gap in series at midline. Vomerine teeth stout and conical, and either of uniform size or becoming progressively slightly larger laterally, but with even smallest teeth in series larger than teeth on premaxilla. Dentary teeth comparable in shape to, but larger in size than, premaxillary teeth and consisting of two or three irregular rows medially that taper to one row laterally.

Maxillary barbel slender, its length slightly greater than distance from anterior margin of orbit to rear of head and approximately three-fourths of HL; barbel origin located ventral to anterior margin of orbit. Medial mental barbel approximately equal in length to lateral mental barbel, with latter slightly 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 slightly beyond posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.33-0.35 of HL. Length of longest branched dorsal-fin ray equal to approximately two-thirds of HL. Dorsal-fin spinelet present. First dorsal-fin ray spinous for basal one-half of length and flexible more distally. First dorsal-fin ray lacking distal filament in all examined specimens including mature males as evidenced by presence of distinctly convex anal-fin margin. Distal margin of dorsal fin convex, with second branched fin ray longest. Dorsal-fin origin located at approximately anterior 0.29-0.30 of SL and along vertical extending through posterior one-half of adpressed pectoral fin. Tip of adpressed dorsal fin extending to vertical through vent. Posterior most dorsal-fin ray with slight basal, posterior, membranous attachment to body.

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

Base of anal fin moderately long. Anal-fin origin located posterior of middle of SL but falling short of middle of TL. Anal-fin margin nearly straight in apparent females, and broadly convex in apparent mature males (see Fig. 1 ). Posterior most anal-fin ray with slight membranous attachment to body.

Pelvic fin 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 reaching anterior margin of vent. 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; spinous portion of ray short, with length slightly more than one-half that of first branched ray and not prolonged as distal filament in any of examined specimens including apparently mature males (as indicated by broadly convex anal-fin margin).

Coloration in alcohol. All available specimens with most of dark pigmentation apparently lost as consequence of postmortem bleaching. Overall coloration of head and body pale. Abdomen pale. Body with small, scattered, rounded, pale brown spots on dorsal and lateral surfaces in some specimens. Dorsal portion of head pale or with few scattered dark spots dorsally and around orbit. Lateral and ventral surfaces of head otherwise pale. Fine stripe of brown spots distributed along middorsal portion of body in one paratype. Other specimens with overall pigmentation very faint and middorsal stripe not apparent.

Dorsal fin pale or with few, scattered, dark spots at base. Anal fin pale or with fine, very widely scattered, dark pigment spots basally. Caudal fin with few, scattered, dark spots basally with remainder of fin pale. Pelvic and pectoral fins pale. All barbels pale.

Sexual dimorphism. A portion of the examined population samples of Cetopsidium ferreirai are characterized by the presence of an anal-fin margin that is broadly convex in contrast to the straight fin margin present in the remainder of the examined material of the species. Such a broadly convex anal-fin margin typifies mature males of other sexually dimorphic species in the Cetopsinae and individuals with that attribute are consequently considered to be mature males. The presumed mature males lack, however, the distal filaments on the first rays of the dorsal and pectoral fins that usually characterize mature males of sexually-dimorphic species within the Cetopsinae .

Distribution. Cetopsidium ferreirai is known only from the rio Trombetas, a left bank tributary of the lower rio Amazonas ( Fig. 2 ; see also under “Remarks”).

Etymology. The species name, ferreirai , is in honor of Efrem J. G. Ferreira of the Instituto Nacional de Pesquisas da

Amazônia (INPA), the collector of all the known specimens of the species, in recognition to his contributions to our knowledge of the fishes of the Brazilian Amazon.

Remarks. In his report on the ichthyofauna of the rio Trombetas basin Ferreira (1995: 52) reported Pseudocetopsis minuta (the Cetopsidium minutum of this study) from four regions within that drainage system. According to our results, Cetopsidium minutum is only known from the Essequibo River basin of Guyana, a considerable distance from the localities from which Ferreira’s material originated. We have examined specimens from Ferreira’s “Região Cachoeira Porteira” (CPT of Ferreira, 1995: Table 3) and “Região Mapuera” (MAP of Ferreira, 1995: Table 3) and find that these population samples represent a previously undescribed species that we describe herein as Cetopsidium ferreirai . Given those findings we assume that Ferreira’s references of Pseudocetopsis minuta from “Região Oriximiná” (ORI of Ferreira,1993: Table 3) and“Região Caxiaporé” (CAX of Ferreira, 1993: Table 3) likely also refer to Cetopsidium ferreirai .

Material examined. 7 specimens (7, 25-37 mm SL). Holotype. Brazil. Pará : rio Trombetas basin, rio Mapuera, last cachoeira before rio Trombetas (approximately 1°05’S, 57°01’W), INPA 10194 , male, 25 mm SL; E. J. G. Ferreira, 19 April 1985 . Paratypes. 6 specimens (6, 25-37 mm SL) Brazil. Pará : rio Trombetas, above Cachoeira Porteira (approximately 1°05’S, 57°01’W), INPA 10193 , 3 (26-33), E. J. G. Ferreira, 19 April 1985 . rio Trombetas , Cachoeira Porteira (approximately 1°05’S, 57°01’W), INPA 6501 , 3 (25-37; 1 specimen, 37 mm, cleared and stained), E. J. G. Ferreira, 19 April 1985 .

Figures

Fig. 1. Cetopsidium ferreirai, new species, holotype, male, INPA 10194, 25 mm SL; Brazil, Pará, rio Trombetas basin, rio Mapuera, last cachoeira before the rio Trombetas (approximately 1°05’S, 57°01"W).

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. 5. Cetopsidium morenoi, INHS 34506, 20.5 mm SL; Venezuela, Guarico, río San Bartolo (8o03’N, 66o42’W).

Fig. 6. Cetopsidium morenoi, mature male, ANSP 165734, 43 mm SL; Venezuela,Apure, Caño Potrerito of río Cinaruco, 24 km S of río Cinaruco on San Fernando de Apure to Puerto Paez Highway (6°25’N, 67°32’W).