Cyphocharax abramoides (Kner 1858)

fisheries: minor commercial

Cyphocharax abramoides (Kner)

Curimatus abramoides Kner, 1859a:142, pl. 2: fig. 3 [type-locality: Brazil: mouth of Rio Negro]; 1859b:76 [abstract of Kner, 1859a, species description].—Günther, 1864:293 [Curimatus abramoides Kner erroneously placed as a synonym of Charax planirostris Gray, 1854; species account, however, based on Kner, 1859a].—Eigenmann and Eigenmann, 1889:431 [Curimatus abramoides considered a synonym of Charax planirostris].—Vari, 1984a:13–16 [removal of Curimatus abramoides from synonymy of Charax planirostris]; 1989a, tables 2, 3 [assignment to Cyphocharax].

Curimatus planirostris.—Günther, 1864:293 [in part, meristic data taken from Kner, 1859a; only C. abramoides citation].—Eigenmann and Eigenmann, 1889:431 [citations in part, not Gronow (= Gronovius) citations; Brazil: Rio Negro, Obidos]; 1891:48 [reference].

Curimatus (Semitapicis) planirostris.—Pellegrin, 1909:148 [Brazil: Santarém].

Semitapicis planirostris.—Eigenmann, 1910:422 [in part, Curimatus abramoides citation; not synonymy of that species in Charax planirostris].—Fernández-Yépez, 1948:36, fig. 16 [in part, Charax planirostris citation; Brazil].—Fowler, 1950:302, fig. 363 [literature compilation, not Gray, 1854, citations]; 1975:375 [reference].—Mago-Leccia, 1971:10 [Venezuela: Río Casiquiare region].

DIAGNOSIS.—The autapomorphic presence of a prominent procumbent spine at the anterior of the dorsal fin (Figure 3) and distinct median keel extending from slightly posterior of the dorsal fin to the anterior of the adipose fin are unique to Cyphocharax abramoides among all curimatids. Similarly the very deep, laterally flattened body also serves to distinguish C. abramoides, not only from its congeners, but also from all other species in the family. Cyphocharax abramoides is further distinguished from its congeners by the 77 to 97 scales in the lateral line, 24 to 30 scales in a transverse series from the lateral line to the origin of the dorsal fin, and 20 to 25 scales in a transverse series from the lateral line to the origin of the anal fin. This contrasts with a maximum of 62 lateral-line scales, 13 scales above the lateral line to the origin of the dorsal fin, and 10 scales below the lateral line to the origin of the anal fin in other Cyphocharax species.

DESCRIPTION.—Body very deep in specimens over 40 mm SL, more so in ripe females, greatly compressed laterally. Dorsal profile of head straight or very slightly concave to tip of supraoccipital spine. Dorsal profile of body smoothly curved from tip of supraoccipital spine to origin of dorsal fin; somewhat convex and distinctly posteroventrally slanted at base of dorsal fin, convex from base of last dorsal-fin ray to caudal peduncle, convexity more pronounced in larger specimens. Dorsal surface of body with indistinct median keel anterior to dorsal fin, with distinct median keel extending from slightly behind posterior terminus of dorsal fin posteriorly to origin of adipose fin. Ventral profile of body gently curved from tip of lower jaw to caudal peduncle. Prepelvic region transversely rounded anteriorly, somewhat flattened with indistinct median keel in region proximate to pelvic fin origin. Well developed, acute median keel posterior to pelvic fin origin. Secondary obtuse keel on each side of postpelvic portion of body about six scales dorsal of ventral midline.

Greatest body depth at origin of dorsal fin, relatively deeper in ripe females, strongly positively allometric until 40 mm SL; body depth 0.48–0.61 (in specimens over 46 mm SL) [0.54]; snout tip to origin of dorsal fin 0.52–0.57 [0.56]; snout tip to origin of anal fin 0.82–0.89 [0.87]; snout tip to origin of pelvic fin 0.58–0.61 [0.58]; snout tip to anus 0.80–0.88 [0.85]; origin of dorsal fin to hypural joint 0.59–0.63 [0.58]. Dorsal fin pointed in profile distally; last unbranched and first branched rays in moderate and larger sized specimens very elongate, extending posteriorly to origin of adipose fin; those elongate rays about five to six times length of ultimate ray. Pectoral fin pointed in profile distally; length of pectoral fin 0.17–0.20 [0.19], extends to or slightly beyond point one-half distance to vertical line through origin of pelvic fin. Pelvic fin pointed in profile distally, length of pelvic fin 0.18–0.24 [0.22], tip reaches nearly to origin of anal fin in small specimens, falling well short of that point in larger individuals. Caudal fin forked. Adipose fin well developed, with relatively elongate base. Anal fin border emarginate, anteriormost branched rays two and one-half to three times length of ultimate ray. Least depth of caudal peduncle 0.12–0.15 [0.14].

Head profile obtusely pointed, head length 0.26–0.31 [0.29]; jaws nearly equal or upper slightly longer than lower, mouth terminal to barely subterminal; snout length 0.26–0.31 [0.27]; nostrils of each side very close, anterior circular, posterior crescent-shaped with aperture closed by thin flap of skin separating nares; orbital diameter 0.30–0.35 [0.34]; adipose eyelid well developed, with vertically ovoid opening over center of eye; length of postorbital portion of head 0.39–0.45 [0.40]; gape width 0.23–0.29 [0.25]; interorbital width 0.43–0.48 [0.45].

Scales somewhat deciduous, more so in smaller individuals. Pored lateral-line scales from supracleithrum to hypural joint 77 to 97 [85]; all scales of lateral line pored, canals in scales straight; 4 to 9 series of pored scales extend beyond hypural joint onto caudal-fin base; 24 to 30 [approximately 24] scales in transverse series from origin of dorsal fin to lateral line; 20 to 25 [approximately 25] scales in transverse series from lateral line to origin of anal fin.

Dorsal fin with anteromedially bifurcate procumbent spine at base of first dorsal-fin ray (Figure 3), spine covered with layer of skin continuous with that underlying scales on proximate portions of body; lateral margins of spine overlain by scales; spine closely associated with and moves in unison with first to first to third dorsal-fin rays (number of rays involved a function of number of unbranched rays); anterior bifurcation of spine less pronounced in larger individuals; dorsal-fin rays (not including procumbent spine) i,9 or ii,9 or iii,9 (ii,9 most common; when three unbranched rays present, first very short) [ii,9]; anal-fin rays ii,7 or 8 or iii,7 or 8 (when three unbranched rays present, first very short) [ii,7]; pectoral-fin rays 13 to 16 [13]; pelvic-fin rays i,8 or 9 (i,8 most common) [i,8].

Total vertebrae 32 (4), 33 (22).

COLOR IN ALCOHOL.—Overall coloration of specimens retaining guanine on scales golden or silvery-golden, darker on dorsal portions of head and body. Ground coloration of specimens lacking guanine on scales tan to brown, darker dorsally. No pronounced pigmentation pattern on head and body. Larger specimens with margins of scales outlined by series of small, dark chromatophores. Fin rays and distal margins of dorsal and adipose fins outlined by series of small, dark chromatophores.

DISTRIBUTION.—Blackwaters of the Rio Negro basin and upper Río Orinoco, and tributaries to lower Rio Amazonas (Figure 4).

AUTAPOMORPHIES OF Cyphocharax abramoides.—The transversely flattened, vertically deep body of Cyphocharax abramoides is unique within the Curimatidae and its hypothesized sister-group the Prochilodontidae (Vari, 1983, 1989a). Similarly the distinct middorsal keel extending from slightly behind the posterior terminus of the dorsal fin to the origin of the adipose fin occurs neither in other curimatids nor in prochilodontids. The overall body form and the middorsal keel are thus considered unequivocal autapomorphies for the species. A third feature, the procumbent spine at the anterior of the dorsal fin (Figure 3) is unique to C. abramoides in the Curimatidae. The spine, which apparently results from the pronounced enlargement of the small first unbranched dorsal fin ray typical of other curimatids, is approximated in the two most speciose genera of the Prochilodontidae, Semaprochilodus Fowler and Prochilodus Agassiz, but is absent in the third prochilodontid genus Ichthyoelephas Posada-Arango. Nonetheless, within the most parsimonious hypothesis of relationships between curimatids and prochilodontids, and among curimatids (Vari, 1983, 1989a), it is most parsimonious to hypothesize that the procumbent spine in Cyphocharax abramoides is autapomorphic for that species in the Curimatidae albeit homoplastically present in most members of the Prochilodontidae.

Two other features of C. abramoides, although derived, occur homoplastically elsewhere in the Curimatidae. Cyphocharax abramoides has the last unbranched and first branched dorsal-fin rays in adults developed into filamentous extensions reaching to the adipose fin in many individuals. Similar elongations of those dorsal-fin rays occur in Curimata cyprinoides (Linnaeus) and C. knerii Steindachner (Vari, 1989c, figs. 28, 31). These extensions were hypothesized synapomorphic for the two species (Vari, 1989c:18), a hypothesis congruent with the distribution of other derived characters in the genus. Under the overall most parsimonious hypotheses of relationships in the Curimatidae (Vari, 1989a) and Curimata (Vari, 1989c) the simplest hypothesis is that the elongate anterior dorsal-fin rays of the C. cyprinoides-C. knerii clade are homoplastic relative to the filamentous rays in Cyphocharax abramoides.

Cyphocharax abramoides has small, relatively deciduous scales contrary to the condition of most of its congeners. The relative size of the scales is reflected both in the number of scales along the lateral line to the hypural joint (77 to 97), and in the number in a transverse series above (24 to 30) and below (20 to 25) the lateral line. No other member of Cyphocharax has such large numbers of scales in these series, nor do such high numbers occur in Curimatella, Steindachnerina, and Pseudocurimata, the other components of the terminal polytomy within the Curimatidae proposed by Vari (1989a). Indeed the only other curimatids with such high numbers of lateral-line scales are the species of Potamorhina Cope with 85 to 110 scales in the lateral-line series. As discussed by Vari (1984:7–8), the high number of scales in Potamorhina on the one hand and Cyphochrax abramoides on the other is evidently homoplastic. This hypothesis was reinforced by the phylogenetic hypothesis for curimatids proposed by Vari (1989a) under which Potamorhina and Cyphocharax are widely separated lineages of the family distinguished by differences in numerous derived features. Thus the small scales of C. abramoides are considered an autapomorphy for the species homoplastically present in the species of Potamorhina.

MATERIAL EXAMINED.—1081 specimens (56, 55.3–212.8).

BRAZIL. Pará: Óbidos, MCZ 20202, 2 (110.0–138.3). Rio Tapajós, Itaituba, USNM 267950, 10 (8, 88.4–96.3). Rio Tapajós, Ilha Tapaiuna, MZUSP 21345, 1. Rio Tapajós, between Itaituba and São Luís, MZUSP 32259, 82. Rio Tapajós, São Luís, MZUSP 22104, 7. Belém, MZUSP 3580, 5. Rio Trombetas, Cuminá, USNM 267951, 20; MZUSP 32261, 836 (15, 90.7–143.6). Rio Trombetas, 20 km from mouth, MZUSP 32260, 12. Lago Jacupá, Oriximiná, MZUSP 5513, 1. Lago Parauacui, Oriximiná, MZUSP 5565, 1. Rio Xingu, Belo Monte, USNM 267952, 5 (124.2–135.5). Santarém, NMW 66904, 1 (122.0); MNHN 09–58–60, 3 (102.7–126.5); NMW 66905, 1. Amazonas: Mouth of Rio Negro, NMW 67402, 1 (133.0, holotype of Curimatus abramoides). Vicinity of Manaus, MZUSP 6686, 9; GC, 1 (140.1). Lower Rio Negro, USNM 229206, 1. Rio Negro, Barcelos, USNM 242137, 4; USNM 289298, 4 (68.8–81.3). Rio Negro, Ilha de Tamaquaré, USNM 242138, 1 (212.8); USNM 289297, 10 (3, 55.3–58.3). Rio Negro, above mouth of Rio Urubaxi, Lago Central of Ilha de Buiu-Açu, USNM 289299, 2 (67.3–69.3). Rio Negro, Paraná de Jacaré, USNM 289295, 1 (116.1); USNM 242139, 1. Rio Negro, Urumari, USNM 242140, 1 (156.3). Rio Negro, Anavilhanas, USNM 267953, 3 (1 specimen cleared and counterstained for cartilage and bone). Rio Negro, Arirará, USNM 289300, 1 (81.1). Rio Negro, Mandiquíe, USNM 242135, 3 (156.0–174.1). Rio Urubaxi, near mouth, USNM 289451, 1 (73.7). Rio Negro, Bucury (= Bucuri), CAS 41732, 1 (77.9). Rio Canumã, MZUSP 7046, 10. Lagoa Central between Rio Camaraú and Rio Apaú, MZUSP 21059, 2. Rio Purus, NMW 66906, 1.

VENEZUELA. Territorio Federal Amazonas: Río Negro at mouth of Río Casiquiare, USNM 289296, 2 (67.0–76.2). Caño Momoni, tributary of Río Casiquiare, MBUCV V-6026, 1. Caño Amanamo, tributary of Río Negro, about 45 km upstream of San Carlos de Río Negro, MBUCV V-11279, 17. Río Negro, about 7 km upstream of San Carlos de Río Negro, MBUCV V-11283, 4. Laguna Titi, San Fernando de Atabapo, MBUCV V-8533, 4. Laguna El Loro, along Río Atabapo, 1 km from San Fernando de Atabapo, MBUCV V-7886, 3.

COLOMBIA. Guainia: Río Guaviare, Cuayare, NRM 26202, 5.