Curimatopsis sabana, Melo, 2020

Melo, Bruno F., 2020, New species of Curimatopsis from the río Caroni, Orinoco basin, Venezuela, with comments on C. macrolepis (Characiformes: Curimatidae), Neotropical Ichthyology (Neotrop. Ichthyol.) 18 (2), pp. 1-12 : 3-6

Curimatopsis sabana , new species

urn:lsid:zoobank.org:act:9CCFF945-1D49-4869-A869-86A943AB7C07

( Fig. 1 , Tab. 1 )

Holotype. AMNH 274996 , 36.5 mm SL, rd, female, Venezuela, Bolívar, río Paragua, above second rapid upriver from the río Carapo mouth, río Caroni , Orinoco basin, approximately 5º35’35”N 63º42’19”W, 26 Feb 1990, C. J. Ferraris & A. Machado-Allison.

Paratypes. All from río Caroni, Orinoco basin, Bolívar, Venezuela. AMNH 91174 , 7 , females, rd, 29.4–43.1 mm SL, collected with holotype . AMNH 91175 , 6 , females, rd, 32.4–39.5 mm SL, río Carapo , near mouth, on right bank at sand beach, approximately 5°36’45”N 63°41’28”W, 19 Feb 1990, A. Machado-Allison & S. Ramirez. AMNH 91186 , 2 , females, 40.5–41.4 mm SL, río Paragua , at second rapid above río Carapo mouth, near right bank, approximately 5°35’33”N 63°42’18”W, 26 Feb 1990, C. J. Ferraris et al. AUM 36458 , 1 , male, rd, 43.6 mm SL, río Paragua , drying pool, 10.3 km E of La Paragua , 6°50’21”N 63°14’14”W, 8 Jun 2003, O. León, P. Pera & N.K. Lujan. LBP 29208 , 2 , females, rd, 31.4–34.1 mm SL, collected with holotype .

Diagnosis. Curimatopsis sabana belongs to the C. macrolepis clade ( C. jaci Melo, Oliveira, 2017 , C. maculosa Melo, Vari, Oliveira, 2016 , C. macrolepis , and C. melanura Dutra, Melo, Netto-Ferreira, 2018 ) and can be easily diagnosed from species of the C. evelynae clade ( C. cryptica Vari, 1982 , C. evelynae , C. guaporensis Melo, Oliveira, 2017 , C. myersi Vari, 1982 , and C. pallida Melo, Oliveira, 2017 ) by having a longer lower jaw that projects past the anterior margin of the upper jaw (vs. lower jaw shorter and not overlapping the upper jaw), and by separate (vs. fused) first and second hypurals. Within the C. macrolepis clade, C. sabana is diagnosed from C. melanura by the absence (vs. presence) of the dark pigmentation on the entire lower lobe of the caudal fin. It differs from C. jaci by the absence (vs. presence) of a distinctly reticulate color pattern on the flanks of females. It is diagnosed from C. maculosa by the possession of a round spot of black pigmentation, sometimes very faint, on the midlateral surface of the caudal peduncle (vs. a small posteriorly pointed spot overlapping the posterior midlateral scales), by the absence (vs. presence) of a gap of two or three scales separating the pigmentation of the midlateral stripe and the dark spot on caudal peduncle, by a deeper body, 34.1– 39.9% of SL (vs. 26.0–31.6% of SL), and deeper caudal peduncle, 13.7–17.4% of SL (vs. 9.0–13.7% of SL). It differs from C. macrolepis by the possession of a circular and weakly pigmented spot on the caudal peduncle (vs. horizontally elongated and strongly pigmented dark spot on caudal peduncle). Finally, it differs from C. microlepis by 26–28 (vs. 57–63) scales in the longitudinal series from the supracleithrum to the hypural joint.

Description. Morphometric data in Tab. 1 . Body relatively short. Dorsal profile of head slightly convex from tip of snout to dorsal-fin origin; gradually descending and nearly straight from dorsal-fin origin to adipose-fin origin and then gently concave to origin of anterior dorsal caudal-fin procurrent ray. Ventral profile more or less evenly convex from chin to terminus of anal-fin base, then gently concave to origin of anterior ventral procurrent ray of caudal fin. Prepelvic region somewhat flattened transversely. Postpelvic region of body transversely rounded.

Head profile acutely triangular with bluntly pointed snout. Lower jaw longer than and projecting past the anterior to limit of upper jaw. Mouth subsuperior, horizontally aligned with center of orbit. Nostrils close; anterior nostrils circular to ovoid, posterior nostrils crescent-shaped with aperture not closed by thin flap of skin separating nares. Adipose eyelid slightly developed anterior to orbit.

Dorsal fin pointed, with distal margin straight and first and second branched rays longest. Distal margin of pectoral fin pointed. Tip of adpressed pectoral fin reaches three or four scales short of vertical through pelvic-fin origin. Pelvic fin profile slightly rounded. Tip of adpressed pelvic fin reaches two to four scales short of anal-fin origin. Caudal fin forked in females and middle caudal-fin rays elongated in males. Adipose fin present. Anal fin emarginate, anterior branched rays one-third length of ultimate ray. Tip of adpressed anal fin reaches two scales short of origin of ventral caudal-fin ray.

Lateral line longitudinal scales from supracleithrum to hypural joint 26 (8), 27* (6) or 28 (5). Pored scales 4 (3), 5* (5), 6 (10), or 7 (1). Continuous series of scales posterior to hypural joint 3 (1), 4* (17) or 5 (1). Scales in transverse series from dorsal-fin origin to pelvic-fin origin 11 (11), 12* (7), or 13 (1). Middorsal series of scales from tip of supraoccipital to dorsal-fin origin 9 (5), 10 (6), 11 (5), or 12* (2). Circumpeduncular scales 16* (19).

Dorsal-fin rays iii,9* (19), first unbranched ray very short. Anal-fin rays iii,7* (19), first ray very short. Pelvic-fin rays i,8* (15), or i,9 (4). Pectoral-fin rays i,12 (2), i,13* (6), i,14 (7), i,15 (3), or i,16 (1). Total vertebrae 27 (4), 28* (11), or 29 (2).

Coloration in alcohol. Ground coloration tan to yellowish. Upper lip, snout, and dorsal portion of head and opercle with small, dark chromatophores; lower jaw with field of dark chromatophores, more so along margin of lower lip. Margins of scales along lateral, dorsolateral, and dorsal surface of body outlined by series of small dark chromatophores, but not forming a clear reticulate pattern; more diffuse pattern of small chromatophores on dorsal and dorsolateral regions of body. Dark pigmentation absent on scales over lateral surface and ventral region of the body. Thin-lying dusky stripe along midlateral surface of body from vertical through dorsal-fin origin to caudal peduncle. Dark concentration of chromatophores covering posterior midlateral scales and anterior portions of middle caudal-fin rays. Rays of dorsal, caudal, and anal fins distinctly outlined by small, dark chromatophores. Pectoral and pelvic fins with scattered, small, dark chromatophores. Adipose fin hyaline with small chromatophores concentrated on distal margin.

Sexual dimorphism. Only one male specimen ( AUM 36458) was identified by its pronounced sexual dimorphism that is typical of species of Curimatopsis ( Vari, 1982) . The specimen has a deeper caudal peduncle (17.4% of SL) than females (13.7–16.2% of SL), slightly elongate middle caudal-fin rays, and a clear enlargement of the penultimate principal ray of the caudal-fin lower lobe. These features are consistent with other species of Curimatopsis presenting sexual dimorphism ( Vari, 1982; Melo, Oliveira, 2017).

Distribution. Curimatopsis sabana is only known from the Carapo and Paragua rivers, which are tributaries of the río Caroni, itself a right-bank tributary of the río Orinoco basin, in the western Guiana Shield in Venezuela ( Fig. 2 ). Various specimens were collected in the region of the río Carapo, near Cerro Guaiquinima (4 km along the river, 300–310 m asl), and one specimen was collected in a drying pool of the lower río Paragua (272 m asl) ( Fig. 3 ). The distribution suggests that C. sabana is restricted to higher elevations of the western Guiana Shield.

Etymology. The specific name sabana refers to the Gran Sabana, a major ecoregion in the western Guiana Shield of southeastern Venezuela, which encompasses the río Caroni basin. A noun in apposition.

Conservation status. Based on Armbruster, Taphorn (2013) who described Neblinichthys peniculatus from the río Carapo, the type locality of Curimatopsis sabana , the region is sparsely populated and difficult to access, which suggests a lack of significant threats for the species. In addition, another relatively recent expedition found one male specimen in the lower río Paragua, increasing the extent of the known occurrence for the species. Although the species lives in a relatively small area of occurrence, this factor alone does not qualify it for a threatened status. Given the available information, C. sabana is herein recommended to be categorized as Least Concern ( LC) under the categories and criteria of the International Union for Conservation Nature ( IUCN Standards and Petitions Subcommittee, 2019).

Figures

FIGURE 1 | Curimatopsis sabana, AMNH 274996, holotype, 36.5 mm SL, female, Venezuela, Bolívar, río Paragua, río Caroni, Orinoco basin (top). AUM 36458, paratype, 43.5 mm SL, male, Venezuela, Bolívar, río Paragua, río Caroni, Orinoco basin (bottom).

FIGURE 2 | Map of northern South America showing the collection localities of species of the Curimatopsis macrolepis clade in the Orinoco and Amazon basins. Note the distribution of C. sabana in highlands of the Guiana Shield. T = type locality.

FIGURE 3 | Habitat of Curimatopsis sabana, AUM 36458, a drying pool of the río Paragua, tributary of the río Caroni. Photograph by J.W. Armbruster.