Comprehensive DescriptionRead full entry
Bryconops collettei ZBK n.sp.
(Figs. 3b, 8)
Holotype . MBUCV-V-30780, 74.0 mm SL; Venezuela : Bolívar : Río Nichare at Wakawajai, tributary of the Río Caura, 6º 19 21 N 64º 57 13 W ; A. Machado-Allison, F. Provenzano, A. Marcano, 6 Dec. 2000 .
Paratypes . All localities in Venezuela : FMNH 109350, 3 (42.8-52.4 mm SL) ; MBUCV-V- 30781, 2 (43.1-52.6 mm SL); collected with the holotype . FMNH 109348, 2 (55.0-58.5 mm SL); Río Caura, beach in front of El Playón , 6º 19 31 N 64º 31 37 W ; A. Machado-Allison et al., 3 Dec. 2000 . FMNH 109347, 1 (46.0 mm SL); Río Caura, Caño at Katuwadi Chenu down-river from El Playón , 6º 19 44 N-64º 31 40 W ; A. MachadoAllison et al., 3 Dec. 2000 . ANSP 139597, 6 (45.9-58.0 mm SL); Río Mato, sandy beach, tributary of Río Caura, 7º 02 N 65º 14 W ; J.E. Bohlke et al., 1 Feb. 1977 .
Additional Material (non-types). FMNH 109349, 20 (10.6-16.0 mm SL); Río Tawadu, raudal Dimoshi Soodii, tributary of the Río Caura, 6º 19 38 N-65º 02 52 W ; A. Machado-Allison et al., 5 Dec. 2000 . ANSP 168006, 18 (33.5-71.0 mm SL) ; MBUCV-V- 21791. 20 (36.0-76.0 mm SL); Río Miamo, on Guasipati-El Miamo road, 20 km S of El Miamo, Río Yuruari/ Cuyuní basin, 7º 38 N 61º 50 W ; S. Schaefer et al., 24 Jan. 1991 . ANSP161536 , 21 (29.0-66.0 mm SL); Río Iguapo, tributary of Río Orinoco, ca. 1 hr. above its mouth by boat. 03º 09 N 65º 28 W ; H. López et al., 13 Mar. 1987 .
Diagnosis. A species of Bryconops , subgenus Bryconops , that is distinguished from all other congeners except B. magoi ZBK by its unique color pattern, in which red coloration occupies the upper half of a diffuse caudal-fin ocellus. It is further distinguished from members of the subgenus Bryconops by the following traits: pored lateral scales 44-48, modally 47 (>57 in B. alburnoides , <31 in B. disruptus and B. durbini , and 43-47, modally 44 or 45, in B. magoi ZBK ); pored lateral scales extending 2-3 scales beyond end of hypural plate onto caudal fin rays (pored lateral scales reaching end of hypural plate and not onto caudal fin rays in B. caudomaculatus ); snout length 4.2-5.4% SL, mean 4.7% (5.8-8.0%, mean 6.8% in B. magoi ZBK ); length of anal fin base 27.3-29.8% SL, mean 28.8% (24.8-27.9%, mean 26.6% in B. magoi ZBK ); and total vertebrae 42-44, modally 43 (40-42, modally 41-42 in B. magoi ZBK ).
Description. Morphometric data are given in Table 3 and a summary of merisitic data appear in Table 2. A moderate to small-sized species of Bryconops , known from specimens less than 70 mm SL. Overall body shape with convex dorsum and slightly rounded belly, tapering to relatively long and slender caudal peduncle. Dorsal fin originating at mid-body and just posterior to insertion of pelvic fin.
Head bullet shaped. Posterior margin of opercle slightly sinusoidal. Second and third infraorbitals not joining ventrally, with a naked area. Third infraorbital moderate in size not reaching the ridge of the preopercle or angle. Eye large. Mouth terminal, opening just ventral to horizontal diameter through orbit. Maxilla not reaching the posterior margin of the second infraorbital; ventro-anterior margin of maxilla not heavily recurved. Outer two rows of premaxillary teeth small and not prominent. Premaxilla with 3-5 teeth, bearing 3- 5 cusps, arranged in two loosely defined rows. Inner premaxillary teeth uniformly five, with 5 to 7 cusps; teeth basically symmetrical, exposed portions wider than high with concave outer surface. Maxilla without teeth or rarely with a single small monocuspid tooth. Dentary with 4-5 large teeth, bearing 5 to 7 cusps, higher than wide, not symmetrical, posterolateral edge prominent, cusps recurved posterolaterally.
Dorsal fin with straight to slightly convex distal margin; either first or second branched ray longest. Posterior base of dorsal fin separated from anterior base of adipose fin by 12 to 14 scales, irregularly arranged. Adipose fin with convex dorsal margin and straight ventral margin. Lobes of caudal fin unequal, upper lobe with rounded tip, lower lobe longer and pointed. Anal-fin origin at level of end of base of the dorsal fin; distal margin of anal fin straight in juveniles and slightly falcate in adults. Pelvic fin not reaching origin of anal fin; distal margin of pelvic fin rounded. Distal margin of pectoral fin pointed and slightly falcate; not reaching pelvic insertion.
Widths of scales on sides of body above lateral line and below row along dorsal fin greater than, or equal to, length of scale; anterior margins of scales almost circular to wavy, with a central notch and rounded posterior margin; circuli present in anterior two thirds of scale; posterior field lacking circuli, possessing 2-3 centrally located, almost parallel, striae.
Dorsal-fin rays: unbranched 2*(54); branched 9*(54); total 11*(54). Anal-fin rays: unbranched 4*(54); branched 25(1), 26(2), 27(6), 28(16), 29(16), 30*(11), 32(2); total 29(1), 30(2), 31(7), 32(16), 33(15), 34*(11), 36(2). Pectoral-fin rays: 11(1), 12*(19), 13(34). Scales: predorsal 10(2), 11(8), 12 (28), 13*(8); lateral 41(5), 42(16), 43(12), 44(14), 45*(10); pored lateral 43(1), 44(11), 45(18), 46(9), 47(13), 48*(5); P-L 1(2), 2(26), 3*(27), 4(2); rows above lateral line 7*(52), 8(1); rows below lateral line 4*(53), 5(1). Gill rakers: upper 6(16), 7(15), 8*(19), 9(4); lower 8(1), 9(1), 10(18), 11*(28), 12(5), 13(1); total 14(1), 15(1), 16(7), 17(11), 18(15), 19*(12), 20(6), 21(1). Vertebrae: precaudal 16(1), 18*(55), 19(2); caudal 23(6), 24(37), 25(14), 26*(1); total 40(1), 41(6), 42(34), 43(16), 44*(1); dorsal fin origin 10(3), 11(42), 12*(13); anal fin origin18*(56), 19(2).
Pigmentation in alcohol. Overall, specimens moderately dusky in preservation, countershaded above and below lateral stripe. Dorsal profile of head dark, fully covered with fine melanophores distributed homogeneously. Anterior area of mouth dark. Orbit with black dorsal and ventral bands. Infraorbitals and preopercle parsely pigmented. Opercle with diffuse spots, almost star-like. Dorsolateral portion of opercle darker. Lateral stripe originating just behind head, somewhat prominent in preservation, increasing in depth and intensity just posterior to dorsal-fin origin, occupying three to four scales rows just behind midbody and ending at caudal peduncle in diffuse, oblong darkened area. Upper lateral scales densely pigmented in central region, tending to form lateral stripes of lightly pigmented spots. Lateral-line canal of the first 14 scales outlined with pigment. Series of melanophores following myosepta below lateral line anterior to vent, extending posteriorly to midpoint of fin base. Anal-fin base with series of melanophores outlining bases of fin rays, forming diffuse band. Dorsal fin partly covered with melanophores, with central area of fin clear. Caudal fin with clear diffuse area in dorsal lobe; remainder of fin covered with melanophores; distal portion of dorsal lobe dark almost black.
Coloration in life (Fig. 3b). Body overall iridescent greenish dorsolaterally turning silver laterally and ventrally. Head usually silver. Iris yellow dorsally and silver ventrally. Cheek and opercular regions silvery. Dorsal area of head, snout, and lower jaw dark. A black stripe extending from opercular opening to caudal peduncle. Below this stripe there is a wider silvery stripe, limited dorsally by an emerald-green metallic stripe. Dorsal fin light red, with a central clear area. Pectoral fins slightly orange. Pelvic and anal fins transparent. Adipose fin intense red. Dorsal lobe of caudal fin with intense red in upper part of diffuse clear area; red color extending posteriorly as streak, almost to end of fin.
Distribution. This new species is known from the Caura and Miamo rivers, Bolívar State, and Rio Iguapo, Amazonas State, Venezuela.
Habitat. Bryconops collettei ZBK is found in habitats with moderate to fast flowing waters over rocky and sandy bottoms. The species is found in both acidic, black waters as well as in clear, but slightly acid waters. In the Caura, it was found in rapids covered by vascular plants (Podostemonacae), as well as in small springs with sandy bottoms. This species inhabits the upper part of the water column in the main channel, usually in schools with other characid species. Cursory examination shows that food items include several groups of terrestrial insects.
Etymology. The species group-name, collettei, is named in honor of Dr. Bruce B. Collette, who has made important contributions to systematic ichthyology and to our careers.
Within species variation. There is important variation in meristic and morphometric traits among populations of B. collettei ZBK , such that the populations from the Río Caura differ from those in the upper Río Orinoco ( Río Iguapo) and from those in the RíoCuyuní ( Río Miamo). The scatters of scores from sPCA (Fig. 9) and RW of morphometric traits or landmarks show that the there is overlap among the phenotypes of the populations but that the Río Caura specimens have longer snouts and anal-fin bases, and shorter orbits (Fig. 7) than do the other B. collettei ZBK . The Río Caura populations also have more numerous lateral and pored scales but fewer total gill rakers, on average, than other populations: 42-45, modally 44 (vs. 41-44, modally 42) lateral scales; 44-48, modally 47 (vs. 43-46, modally 45) pored scales; and 14-19, modally 16 (vs. 17-21, modally 18) gill rakers, respectively. Without other evidence, we do not recognize these populations as separate species due to the large degree of overlap among them. These differences may be due to environmental influences upon the phenotype (see Sidlauskas et al. 2006); for example, the waters of the Río Caura are much more basic (pH> 6.2) than the waters in the other rivers (pH<5.7). However, this is speculation at present. As a precaution, we have restricted the types to the Río Caura populations.