Cetopsidium morenoi (Fernández-Yépez, 1972)

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: 138-144

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scientific name

Cetopsidium morenoi (Fernández-Yépez, 1972)
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Cetopsidium morenoi (Fernández-Yépez, 1972)   Figs. 2 View Fig , 4-6 View Fig View Fig View Fig , Tables 2-8

Hemicetopsis morenoi Fernández-Yépez, 1972a: 19   , unnumbered Fig. on page 20 [type locality: río Aguaro, 1 Km. abajo del paso Garcerito, al Oeste franco de Santa Rita, Estado Guárico, Venezuela (= Venezuela, río Aguaro, 1 km below Paso Garcerito, directly west of Santa Rita, State of Guárico)].– Machado-Allison et al., 1993: 65 [ Venezuela, Guarico, ríos Aguaro and Guariquito].

Hemicetopsis cf. morenoi   .– Taphorn et al., 1997: 85 [ Venezuela].

Pseudocetopsis morenoi   .–Evers & Seidel, 2002: 741 [listing].– Vari & Ferraris, 2003: 259 [in check list; distribution].

Diagnosis. Cetopsidium morenoi   differs from C. ferreirai   in the distal prolongations of the first rays on the dorsal and pectoral fins (present in at least some, presumably mature males, see Fig. 6 View Fig , versus absent in all specimens, respectively), in the overall form of the head (with well-developed, distinctlybulging adductor mandibulae muscles and with the snout not distinctly rounded versus with head less massive due to less extensive development of the adductor mandibulae on the dorsal surface of the head and with snout distinctly rounded, respectively; compare Figs. 4-6 View Fig View Fig View Fig with Fig. 1 View Fig ), and in the degree of development of the dark pigmentation on the body (dark pigmentation present over much of the lateral and dorsal surfaces of the body versus the near the absence of dark pigmentation on the lateral surface of the body and with the pigmentation limited to the middorsal region of the body, respectively). Cetopsidium morenoi   differs from C. minutum   in the length of the pelvic fin (falling short of the anterior limit of the vent versus reaching to the anal-fin origin, respectively) and in the length of the pectoral fin excluding the distal filament of the first fin ray in mature males (falling distinctly short of the vertical through the pelvic-fin insertion versus reaching to that line, respectively). Cetopsidium morenoi   differs from C. orientale   in the alignment of the dorsal and ventral profiles of the portion of the body posterior of the dorsal fin (converging posteriorly versus running in parallel, respectively) and apparently in the degree of the development and extent of the dark pigmentation on the body (extensive dark pigmentation not extending onto anal fin but with semicircular dark spot at the base of the dorsal fin versus with limited dark pigmentation extending onto the base of the anal fin in at least some specimens and without the dark blotch of pigmentation at the base of the dorsal fin, respectively), the pigmentation of the rayed portion of the caudal fin (absent versus present on at least the basal one-half of fin, respectively), the middorsal pigmentation on the body posterior of the terminus of the dorsal fin (distinct stripe absent versus present, respectively), and the dark pigmentation on the lower jaw (a single, often incomplete, row of chromatophores versus a broad band of chromatophores, respectively). Cetopsidium morenoi   differs from C. pemon   in the form of the dark pigmentation on the body (formed of large stellate chromatophores versus small, point-like, scattered chromatophores over the dorsal and lateral surfaces of the head), and in the degree of development of the adductor mandibulae muscles (very well-developed and distinctly obvious on the dorsolateral portion of head versus moderately-developed and not distinctly obvious externally, respectively). Cetopsidium morenoi   differs from C. roae   in the location of the vent (located 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), in the alignment of the dorsal and ventral profiles of the portion of the body posterior of the dorsal fin (converging posteriorly versus running in parallel, respectively), and in the form of the dark pigmentation on the body (formed of large, stellate chromatophores versus small, point-like chromatophores scattered over the dorsal and lateral surfaces of the head, respectively).

Description. Body moderately robust, somewhat compressed laterally anteriorly and becoming progressively distinctlycompressed posteriorly. Body depth at dorsal-fin origin approximately 0.22-0.25 of SL, and approximately equal to, or slightly less than, HL. Lateral line on body incomplete, unbranched, and midlateral; extending from vertical through pectoral-fin base posteriorly to region dorsal to 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 slightly posterodorsally-inclined along base of anal fin. Caudal-peduncle depth approximately equal to caudal-peduncle length.

Head in profile acutely triangular overall with bluntlypointed snout. Dorsal profile of head convex anteriorly and then straight to vertical through posterior margin of orbit and convex from that point to nape. Ventral profile of head variably convex. Margin of snout in dorsal view ranging from rounded to bluntly triangular. Postorbital margins of head slightly convex on each side from dorsal view. Enlarged jaw musculature very evident externally on dorsal and dorsolateral 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-half 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 extending through pectoral-fin insertion; eye visible in dorsal view, but not in ventral view, of head. Middle of orbit at approximately anterior 0.25-0.30 of HL. Eye diameter approximately one-third 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-half of orbit; narial opening nearly round and with flap of skin extending along anterior two-thirds of rim of aperture, with flap highest anterolaterally.

Mouth subterminal; its width approximately 0.60 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 irregular rows of uniform-sized teeth medially and tapering to one row laterally. Vomerine teeth arranged in single, arched row with distinct gap in series at midline. Vomerine teeth stout, conical, and of approximately uniform size, 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 arranged in two or three, irregular rows medially that taper to one row laterally.

Maxillary barbel slender, its length approximately slightly greater than 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 slightly shorter than lateral mental barbel, with latter 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 past, posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.32-0.37 of HL. Longest branched dorsal-fin ray, excluding distal filament when present, equal in length to approximately two-thirds of HL. Dorsal-fin spinelet present, first dorsal-fin ray spinous for basal one-half of its length and flexible more distally, with distal filament present in at least some specimens. Distal margin of dorsal fin slightly convex, with first branched ray longest. Dorsal-fin origin located at approximately anterior 0.31-0.34 of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin reaching 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 rounded. Length of longest caudal-fin ray approximately two times length of middle fin rays.

Base of anal fin moderately long. Anal-fin origin located distinctly posterior of middle of SL and approximately at middle of TL.Anal-fin margin nearly straight in most examined specimens, but convex in presumed mature males as evidenced by their distinct filamentous first rays of dorsal and pectoral fins ( Fig. 6 View Fig ). 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 barely 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, excluding distal filament on first ray in mature males, 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, prolonged as filament in some, presumably male, specimens ( Fig. 6 View Fig ).

Coloration in alcohol. Overall ground coloration of head and body pale and overlain with rounded, brown chromatophores. Chromatophores variably large in most examined specimens (compare Figs. 4 View Fig to 6), but relatively small is some individuals from western portions of the distribution of the species. Dark pigmentation on head and body tends to be more concentrated dorsally, with denser concentration of dark pigmentation middorsally posterior of base of dorsal fin. Expanded chromatophores blend together to form uniform brown cast on some portions of body in most specimens ( Fig. 4 View Fig ), but constricted and distinctly separated in other individuals ( Fig. 5 View Fig ), particularly in population samples from the western portions of the distributional range of the species. Ventral surfaces of abdomen and head pale. Lower lip with single row of dark chromatophores paralleling margin of lip; number of dark chromatophores on lip reduced in some population samples from western portion of the distributional range of the species.

Dorsal fin pale with dark pigmentation forming semicircular basal spot in overall heavily pigmented specimens. Spot at base of dorsal fin ranging from being limited to base of fin to extending to variable degrees beyond basal portions of middle rays of fin. Anal fin pale with scattered, dark chromatophores basally; pigmentation sometimes forming discrete dark spots ( Figs. 5 View Fig , 6 View Fig ). Caudal fin with dark pigmentation along fleshy basal areas and sometimes with dark pigmentation either outlining fin rays or forming spots on interradial membranes. Pelvic and pectoral fins pale.

Maxillary barbel dusky basally and pale distally. Mental barbels pale.

Sexual dimorphism. The presumed mature males of Cetopsidium morenoi   have filaments on the first rays of the dorsal and pectoral fins and have the anal-fin margin broadly convex ( Fig. 6 View Fig ) rather than being straight or nearly straight as is the case in conspecific females and immature males ( Figs. 4 View Fig , 5 View Fig ). Distribution. Cetopsidium morenoi   is known from the central and western portions of the río Orinoco basin in Venezuela and Colombia ( Fig. 2 View Fig ).

Remarks. The type series of Hemicetopsis morenoi   was reported by Fernández-Yépez (1972a: 19) to consist of a holotype and two paratypes. That author neglected to cite either catalog numbers for those lots or the institution in which the specimens were deposited. None of the types of H. morenoi   were cited as extant in a relatively recent compendium of types deposited in various Venezuelan fish collections ( La Marca, 1997). Neither are those specimens known to be present in the holdings of MBUCV (F. Provenzano; pers. commun., 1998); a collection that does include at least portions of the type series of other species of fishes described by Fernández-Yépez ( Provenzano et al., 1998: 1). We have, however, examined specimens that we identify as H. morenoi   that originated at the type locality of that species and that conform with the information provided in the original description of that species by Fernández- Yépez (1972a).

Fernández-Yépez (1972a) reported the presence of two other species of the Cetopsinae   at the type locality of Hemicetopsis morenoi   and identified these forms as H. minutus   and H. macilentus   (= Cetopsidium minutum   and Denticetopsis macilenta   of this study, respectively). Our analysis indicate, however, that both of those species are endemic to the Essequibo River basin of Guyana, a river system that lies a significant distance from the site in the río Orinoco basin from which the samples examined by Fernández-Yépez originated. A comparison of a size range of samples of H. morenoi   with the specimens illustrated by Fernández-Yépez (1972a) indicates that these two additional “species” reported by Fernández-Yépez most likely represent different earlier ontogenetic stages of D. morenoi   .

Some specimens in a sample of Cetopsidium morenoi   from the western portions of the range of the species from the río Meta basin in Colombia (ANSP 139574) agree with the type species of C. morenoi   in most examined features. These Colombian specimens differ, however, from the population samples of that species that originated closer to the type locality in having an overall lighter pigmentation. The río Meta samples also differ in having the brown chromatophores in many specimens that are constricted and separate rather than being large and coalesced with each other as is condition typical in many other examined population samples of C. morenoi   . Further material is necessary to evaluate whether these differences are significant. Until such analyses are possible, the río Meta populations are tentatively identified as C. morenoi   .

Two lots from outside the core range of Cetopsidium morenoi   (MCNG 21688, río Sipapo; MCNG 7623, río Cataniapo) consisted of rather depigmented material; a situation that renders a definitive identification to species impossible. Nonetheless, these specimens agree with that species in meristics, morphometrics, and other examined features and are tentatively identified herein as C. morenoi   .

The report of “ Hemicetopsis   cf. morenoi   from Venezuela by Taphorn et al. (1997: 85) presumably refers to Cetopsidium morenoi   . That species was originally described from specimens collected in Central Venezuela.

Material examined. 53 specimens (16-43 mm SL). Colombia. Meta: Quebrada Ventrurosa , 0.25 creek miles (0.4 km) above road between La Balsa and Puerto Lopez, río Meta drainage (4°05’N, 72°58’W), ANSP 139574 View Materials , 2 View Materials (28-37) GoogleMaps   . Venezuela. Amazonas: río Sipapo, approximately 150 m from Salto Remo (4°34’28"N, 67°18’31"W), MCNG 21688 View Materials , 1 View Materials (28) GoogleMaps   . 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), ANSP 165734 View Materials , 14 View Materials (27- 43) GoogleMaps   . río Cataniapo, Caño Carinaqua , MCNG 7623 View Materials , 5 View Materials (20-38)   . Guarico: río San Bartolo (8 o 03’N, 66 o 42’W), INHS 34506 View Materials , 1 View Materials (20.5) GoogleMaps   ; INHS 34065 View Materials , 12 View Materials (16-31.5) GoogleMaps   ; INHS 34860 View Materials , 1 View Materials (24.5)   ; INHS 61868 View Materials , 1 View Materials (22)   ; INHS 61937 View Materials , 7 View Materials (16-40)   ; INHS 69416 View Materials , 8 View Materials (22-33)   . río Mocapra (7°56’N, 66°46’W), INHS 34301 View Materials , 2 View Materials (26.5-34.5) GoogleMaps   . Río Aguaro (7°47’N, 66°25’W), INHS 34356 View Materials , 3 View Materials (18-24.5) GoogleMaps   . Río San Jose (8°01’N, 67°21’W), INHS 34613 View Materials , 1 View Materials (22) GoogleMaps   ; INHS 34648 View Materials , 1 View Materials (29) GoogleMaps   . Río Aguas Muertas in Las Payaras, Parque Nacional Aguaro-Guariquito (8°08’01"N, 66°40’53"W), MCNG 31796 View Materials , 3 View Materials GoogleMaps   (23-36).

Cetopsidium orientale (Vari, Ferraris & Keith, 2003)   Figs. 2 View Fig , 7 View Fig , Tables 2-8

Hemicetopsis sp.   – Boujard et al., 1990: 347 [ French Guiana, Fleuve Arataye]. – Ponton & Copp, 1997: 241 [ French Guiana, Fleuve Sinnamary]. – Boujard et al., 1997: 126, pl. 18 [ French Guiana, Fleuve Approuague].

Pseudocetopsis sp.   – Lowe-McConnell, 1991: 69 [ Brazil, upper rio Xingu Basin, Suiá Missu Lakes (=flood plain lakes along upper portion of rio Suiá Missu)].

Pseudocetopsis cf. minutus   .– LeBail et al., 2000: 146, fig. [ French Guiana, Fleuve Maroni, Fleuve Iracoubo, Fleuve Comté, Fleuve Oyapock].

Pseudocetopsis orientale Vari et al., 2003: 693   , fig. 1 [type locality: Suriname, Brokopondo District, Mindrineti Kreek, close to mouth of Maykaboeka Kreek, Saramacca River   GoogleMaps basin, on Gros Rosevel Mining   GoogleMaps concession (5°07’08.8"N, 55°16’59.4"W)].

Diagnosis. Cetopsidium orientale   differs from C. ferreirai   in the degree of development of the first rays of the dorsal and pectoral fins (with distal filaments present in presumed males as indicated by the possession of a distinctly convex anal-fin margin versus distal filaments absent in such specimens, respectively), the relative depth of the body (0.21-0.23 of SL versus 0.18-0.20 of SL, respectively), the overall coloration pattern (dark pigmentation widely distributed over dorsal and lateral of body versus limited dark pigmentation situated primarily along middorsal region of body, respectively). Cetopsidium orientale   differs from C. minutum   in the length of the pelvic fin (reaching posteriorly to the anterior margin of the vent versus to the anal-fin origin, respectively), the relative depth of the body (0.21-0.23 of SL versus 0.17-0.19 of SL, respectively), and in the length of the pectoral fin (tip falling distinctly short of the vertical through the pelvic-fin insertion versus reaching that line, respectively). Cetopsidium orientale   differs from C. morenoi   in the alignment of the dorsal and ventral profiles of the portion of the body posterior of the terminus of the base of dorsal fin (running in parallel versus converging posteriorly, respectively), in the degree of development and extent of the dark pigmentation on the body (limited dark pigmentation extending onto the base of the anal fin in at least some specimens and without dark blotch of pigmentation at the base of the dorsal fin versus extensive dark pigmentation falling short of the base of the anal fin and with a semicircular dark spot present at the base of the dorsal fin, respectively), the distribution of dark pigmentation on the rayed portion of the caudal fin (present on at least basal one-half of fin versus absent, respectively), the form of the dark pigmentation on the middorsal portion of the body posterior terminus of the base of dorsal fin (distinct stripe present versus absent, respectively), and the degree of development of dark pigmentation on the lower jaw (pigmentation in form of a broad band versus consisting of single, often incomplete, row of chromatophores, respectively). Cetopsidium orientale   differs from C. pemon   in its overall coloration (large, stellate, dark chromatophores densely covering dorsal and lateral surfaces of the head and body versus the small, pointlike chromatophores scattered over the dorsal and lateral surfaces of the head and body, respectively), 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 inclination of the predorsal region of the body and head (slightly inclined versus distinctly inclined, respectively). Cetopsidium orientale   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 that structure, respectively) and in the overall coloration (large, stellate, dark chromatophores densely covering the dorsal and lateral surfaces of the head and body versus the small, point-like chromatophores scattered over the dorsal and lateral surfaces of the head and body, respectively).

Description. Body moderately robust, somewhat compressed laterally anteriorly and becoming progressively distinctlycompressed posteriorly. Body depth at dorsal-fin origin approximately 0.21-0.23 of SL, and approximately equal to distance from anterior margin of eye to posterior margin of opercle. Lateral line on body incomplete, unbranched, and midlateral; extending from vertical through pectoral-fin base posteriorly to point within region delimited anteriorly by vertical through middle of base of anal fin and posteriorly by vertical located proximate to anterior terminus of caudal peduncle. Dorsal profile of body straight, or nearly straight, from nape to dorsal-fin origin and straight from that point to caudal-fin base. Ventral profile of body slightly convex along abdomen, approximately straight along base of anal fin and running parallel posteriorly with dorsal profile of body. Caudal-peduncle depth greater than caudal-peduncle length.

Head in profile acutely triangular overall, with bluntlypointed snout. Dorsal profile of head straight to slightly convex 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 at approximately anterior 0.30 of HL. Eye diameter approximately one-third of snout length. Interorbital width approximately equal to distance from tip of snout to point lying within region between middle of eye and 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 middle of orbit. Posterior narial opening located on dorsal surface of head, situated dorsal to anterior one-third of orbit; narial opening rounded and nearly encircled by flap of skin, but with small gap posteriorly and flap highest anterolaterally.

Mouth subterminal; its width approximately 0.60 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, sharply-pointed, and arranged in three regular rows of uniform-sized teeth across entire premaxilla. Vomerine teeth arranged in single, arched row, with distinct gap in tooth series at midline. Vomerine teeth conical, all of approximately uniform size, and with largest teeth in series approximately same size as largest teeth on premaxilla. Dentary teeth comparable in shape to, but slightly larger than, premaxillary teeth. Dentary dentition consisting of three irregular tooth 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 slightly shorter than lateral mental barbel, with latter 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 barely beyond, posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.38-0.40 of HL. Longest branched dorsal-fin ray, excluding distal filament present in mature males, equal in length to approximately two-thirds of HL. Dorsal-fin spinelet present, first dorsal-fin ray spinous for basal onehalf of length but flexible more distally, and with distal filament present in mature males. Distal margin of dorsal fin slightly convex, with first branched ray longest. Dorsal-fin origin located at approximately anterior 0.29-0.33 of SL and along vertical extending through middle of adpressed pectoral fin. Tip of adpressed dorsal fin, excluding distal filament present on first ray in mature males, reaching to vertical through anterior margin of vent. Posterior most dorsal-fin ray with slight, basal, posterior, membranous attachment to body.

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

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 in most examined specimens, but convex in presumed mature males as evidenced by presence of distal filamentous first dorsal- and pectoral-fin rays. 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 passing 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, excluding elongate filament on first ray in mature male specimens, slightly more than 0.60 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 prolonged as filament beyond margin of fin in presumed mature males.

Coloration in alcohol. Overall ground coloration of head and body pale and overlain with large, rounded, brown chromatophores. Dark pigmentation on head and body tends to be more concentrated dorsally. Expanded chromatophores blend together to form uniform brown cast on some to major portions of body in most specimens. Head with distinct, dark spots on regions anteroventral, ventral, posteroventral, and posterior to orbit. Ventral surface of abdomen and head pale except for scattered, dark, chromatophores on abdomen in some specimens and broad band of scattered, dark chromatophores extending from symphysis of lower jaw to opercle.

Dorsal fin pale with some dark pigmentation basally forming somewhat diffuse spot with dorsal margin in form of semicircle.Anal fin pale with scattered, dark chromatophores along basal portions of fin. Pelvic and pectoral fins pale. Caudal fin with few, scattered, dark chromatophores extending distally to at least middle of fin rays.

Maxillary barbel with scattered, dark pigmentation basally and pale distally. Mental barbels pale.

Coloration in life. LeBail et al. (2000: 147) provided a photograph of a live specimen of Cetopsidium orientale   (identified therein as Pseudocetopsis cf. minutus   ), photographed in an aquarium immediately after capture. The overall dark pigmentation visible in the specimen in the photograph is comparable to that described above for preserved specimens, but the head, body, and fins of the photographed individual have an overlying silvery sheen that is absent in preserved individuals.

Sexual dimorphism. The presumed mature males of Cetopsidium orientale   have filaments present on the distal portions of the first rays of the dorsal and pectoral fins and have the anal-fin margin slightly convex. Females and immature males of the species, in contrast, lack filaments on these fins and have a straight anal-fin margin.

Distribution. Cetopsidium orientale   is known from the coastal rivers of Suriname and French Guiana in the region from the Corantijn River along the border between Suriname and Guyana to the Fleuve Oyapock-rio Oiapoque along the French Guiana-Brazil border ( Fig. 2 View Fig ). Given the presence of this species in the Surinamese tributaries of the Corantijn River, it is likely that is also occurs in the left bank tributaries to that river draining from Guyana. Similarly it is likely that C. orientale   also occurs in the portions of the rio Oiapoque basin within Brazil. Material tentatively identified as this species originated in the rio Tocantins and rio Xingu (see “Remarks” below).

Ecology. The type locality of Cetopsidium orientale   is a rainforest stream bordered by overhanging vegetation that at the time of collection of the type series had shallow (40 cm deep), clear, slowly-moving water over a sand bottom with mud along the banks. The holotype and paratypes captured at that locality were living in holes and fissures in decaying branches submerged along the side of the stream. Mol et al. (2000: 430) characterize the Maykaboeka Creek as a low-gradient, second order drainage running through undisturbed rainforest. Non-type specimens from Degrad Florian in the Fleuve Iracoubo basin, French Guiana (MNHN 2002-1101) were captured in a stream approximately 3 m wide and 10-59 cm deep in clear, but slightly tea-colored, waters in areas with slow current densely shaded by the gallery forest. During the day C. orientale   lies hidden in the sediment under leaves or roots (Philippe Keith, MNHN; pers. commun., 2002) in various localities within French Guiana. Observations of C. orientale   by the senior author in the western limit of the species distribution in the Corantijn River along the Surinamese-Guyanese border indicate that the species lives in similar habitats in that region.

Remarks. In addition to the specimens reported on by Vari et al. (2003: 693), two lots of Cetopsidium   from the rio Tocantins and rio Xingu basin agree with C. orientale   in all examined features although having originated in localities lying considerable distances south of the previous known range of the species. One of these lots was collected by H. (=Harald) Schultz at an unspecified locality in the rio Araguaia basin sometime before 1961 at which time the specimens were catalogued into the collections of MNRJ. Schultz (1961: 65) documented his trip to Bananal Island (= Ilha do Bananal) in the rio Araguaia and it is possible that the specimens originated from that area. This area is proximate to the collecting site of the only known other sample of the species from outside of the Guianas (BMNH 1985.6.20.943-944) that originated in the southeastern tributaries of the upper rio Xingu system near the divide with the rio Araguaia basin and not far from the southern portions of the Ilha do Bananal (see Lowe- McConnell, 1991, fig. 1). The latter specimens were reported on by Lowe-McConnell (1991:69) as Pseudocetopsis sp.  

Material examined. 68 specimens (18-58 mm SL). Brazil. Mato  

Grosso: Lakes near rio Suiá Missu (=Suiá-Miçu), BMNH 1985.6.20.943-944, 3 (21-23). rio Araguaia, MNRJ 9523, 4 (31.5- 33). French Guiana. No specific locality, MNHN 2002-1103, 3 (37.5-38.5). Arataye River, Saut Parare (4 o 03’N, 52 o 42’W), MNHN 1994-0092, 1 (29.5). Crique Boulanger of Fleuve Comté (4°36’N, 52°19,W), MNHN 2002-1099, 2 (38-38.5). Crique Balatée of Fleuve Maroni (5°29’N, 54°03’W), MNHN 2002-1098, 2 (43-49); MNHN 2002-1100, 1 (22). Degrad Florian of Fleuve Iracoubo (5°29’N, 53°33’W), MNHN 2002-1101, 8 (24-44). Fleuve Oyapock [=rio Oiapoque], MNHN 2002-1102, 11 (40-58). Suriname. Kaiserberg River (approximately 3°03’N, 56°35’W), FMNH 96268, 1 (25). Brokopondo District: Mindrineti Kreek, close to mouth of Maykaboeka Kreek, Saramacca River basin, on Gros Rosevel Mining concession (5°07’08.8"N, 55°16’59.4"W), MHNG 2621.040, 1 (27, holotype of Pseudocetopsis orientale   ); MHNG 2621.044. 2 (22-22, paratypes of P. orientale   ); MHNG 2621.039, 4 (21-26, paratypes of P. orientale   ); MHNG 2626.013, 9 (18-27, paratypes of P. orientale   ); USNM 369732, 2 (21-24, paratypes of P. orientale   ); MNHN 2002.1625, 1 (26, paratype of P. orientale   ); NZCS F7048, 1 (23, paratype of P. orientale   ). Maykaboeka Creek, Gros Rosevel area, area of Golden Star Concession (5°4’45"N, 55°16’09"W), MZUSP 65404, 1 (27, paratype of P. orientale   ). Nickerie District: Stream near Avanavero, approximately 3 miles (=4.8 km) downstream of DeVis Falls (approximately 4°48’N, 57°26’W), AMNH 54828, 1 (22). Small stream on Lucie River camp to Paramaribo Road, 25 km N of Sisa Creek (approximately 3°34’N, 57°37’W), AMNH 55001, 1 (32). Woodland stream, 0.5 km from Camp Mataway (4 o 48’N, 57 o 43’W), USNM 226146, 2 (22-23). Stream near Camp Anjoemara (4 o 50’N, 57 o 26’W), USNM 226147, 6 (18-24; 2 specimens, 20-21 mm, cleared and stained); MZUSP 79285, 1 (22; specimen cleared and stained). Stream at km 212 of Amotopo to Camp Geology Road, at Machine Park - Camp 212 (3 o 50’N, 57 o 34’W), USNM 226148, 1 (30).

MNRJ

Museu Nacional/Universidade Federal de Rio de Janeiro

MNHN

Museum National d'Histoire Naturelle

FMNH

Field Museum of Natural History

MHNG

Museum d'Histoire Naturelle

USNM

Smithsonian Institution, National Museum of Natural History

NZCS

University, National Zoological Collection of Suriname

MZUSP

Museu de Zoologia da Universidade de Sao Paulo

AMNH

American Museum of Natural History

Kingdom

Animalia

Phylum

Chordata

Class

Actinopterygii

Order

Siluriformes

Family

Cetopsidae

Genus

Cetopsidium

Loc

Cetopsidium morenoi (Fernández-Yépez, 1972)

Vari, Richard P., Ferraris Jr, Carl J. & de Pinna, Mário C. C. 2005
2005
Loc

Pseudocetopsis cf. minutus

LeBail., P & Fascicule II 2000: 146
2000
Loc

Hemicetopsis cf. morenoi

Taphorn, D & Royero, A 1997: 85
1997
Loc

Pseudocetopsis sp.

Lowe-McConnell, R 1991: 69
1991
Loc

Hemicetopsis morenoi Fernández-Yépez, 1972a: 19

Machado-Allison, A & Mago-Leccia, O & Castillo, R & Royero, C & Marrero, C 1993: 65
Fernandez-Yepez, A 1972: 19
1972