Taxonomic Study of Hoplias Aimara (Valenciennes, 1846) and Hoplias macrophthalmus (Pellegrin, 1907) (Ostariophysi, Characiformes, Erythrinidae)

The taxonomy of the nominal species of giant trahiras Hoplias aimara (Valenciennes, 1846) and Hoplias macrophthalmus (Pellegrin, 1907), both described from Cayenne (French Guiana), was evaluated to determine whether they constitute distinct forms and to determine the geographic distribution of the recognized species. A total of 200 specimens were examined (30–624 mm standard length). Analysis of meristic and morphometric data resulted in the recognition of a single species. Study of the type-specimens revealed that both species names, H. aimara and H. macrophthalmus, refer to the same taxon. According to the Principle of Priority of the International Code of Zoological Nomenclature the name Hoplias aimara has precedence. This species is distinguished from congeners by the presence of a vertically-elongate dark spot on the median portion of the opercular membrane and by the absence of the accessory ectopterygoid. Hoplias aimara occurs in the drainages of Rio Tocantins, Rio Xingu, Rio Tapajós, Rio Jarí, and Rio Trombetas, in coastal drainages of the Guyanas, Suriname, and state of Amapá, Brazil. In the Río Orinoco basin, the species occurs only in the Río Caroní and rivers to the east of this drainage. Literature records of Hoplias aimara for the Rio Purus and upper Río Orinoco were based on misidentifications. This pattern of geographic distribution of Hoplias aimara in rivers of the Guyanas and Brazilian Shields also occurs in other Neotropical species of fishes.

Figure 1

Hoplias aimara: (A) FMNH 109458, 46.9 mm SL; (B) MZUSP 87964, 355.3 mm SL. Arrow indicates vertically-elongate dark spot on opercular membrane.

Figure 2

Ventral view of anterior right portion of cranium and suspensorium of (A) Hoplias aimara, MZUSP 41513, 107.4 mm SL and (B) H. malabaricus, MZUSP 47720, 146.8 mm SL. Abbreviations: AC ECT, accessory ectopterygoid; ECT, ectopterygoid; END, endopterygoid; MAX, maxilla; PMX, premaxilla; VOM, vomer.

Figure 3

Ventral view of head of (A) Hoplias aimara, MZUSP 21835, 136.3 mm SL and (B) H. malabaricus, AMNH 74691, 167.2 mm SL.

Figure 4

Lateral view, left infraorbital series of (A) Hoplias aimara, MZUSP 41513, 107.4 mm SL and (B) H. aimara, MZUSP 47694, 191 mm SL. Abbreviations: 1–6, infraorbitals one to six.

Figure 5

Map of central and northern South America showing geographic distribution of Hoplias aimara based on material examined in this study. Some dots may represent more than one lot. Square indicates the type locality of H. aimara and H. macrophthalmus.

Figure 6

(A) Hoplias aimara, holotype, MNHN A-9968, 765 mm SL, Cayenne, French Guiana; (B) Hoplias macrophthalmus, holotype, MNHN A-9770, 275 mm SL, Cayenne, French Guiana.

Figure 7

Head length versus orbital diameter for Hoplias aimara (dots) and H. malabaricus (circles). Only specimens of H. aimara smaller than 385 mm SL included.

Contributor Notes

(GMTM, MT-P) Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, P.O. Box 11461, São Paulo/SP, Brazil; and (OTO) Sec¸ão de Peixes, Museu de Zoologia da Universidade de São Paulo, P.O. Box 42594, São Paulo/SP, Brazil. E-mail: (GMTM) georgemattox@uol.com.br. Send reprint requests to GMTM.

Received: 29 Jul 2005

Accepted: 20 Feb 2006