Sunday, February 4, 2018

[Ichthyology • 2018] Charax awa • A New Species of Charax (Characiformes, Characidae) from northeastern Brazil


Charax awa
Guimarães, De Brito, Ferreira & Ottoni, 2018


Abstract
Charax awa sp. n. is herein described from the Rio Mearim, Rio Munim and Rio Turiaçu basins, three coastal river basins of northeastern Brazil located between the Rios Gurupi and Parnaíba basins. These have a complex and still poorly known biogeographic history. This region is ecologically extremely relevant since it comprises three of the main Brazilian biomes, as well as, transition zones between them: Amazônia, Brazilian Cerrado and Caatinga. Therefore, this area has faunal and floristic representatives of these three biomes, which makes it particularly relevant in terms of ecology, biodiversity and conservation. Charax awa sp. n. possesses a relatively small orbital diameter (22.1–28.5 % HL), what distinguishes it from most of its congeners, except from C. notulatus and C. caudimaculatus. It differs from C. caudimaculatus by a longer snout, and from C. notulatus by the number of scales around the caudal peduncle, as well as by the number of vertebrae. The new species herein described differs from its geographically closely distributed congeners, C. leticiae, C. niger, and C. pauciradiatus mainly by the relative horizontal orbital diameter. It is a “small-eyed” species. In addition, C. awa sp. n. can be distinguished from C. leticiae by having a maxilla extending to the vertical line posterior to the pupil, near the posterior orbital margin and by having a lower humeral spot distance. It can be distinguished from C. pauciradiatus by more scale rows from the pelvic-fin origin to the lateral line and more scale rows from the dorsal-fin origin to the lateral line and it differs from C. niger by having more transverse scale rows in space from the humeral spot to the supracleithrum. In addition, it differs from C. pauciradiatus and C. niger by the absence of bony hooks on anal and pelvic-fins rays of adult males.

Key Words: Characinae, Characini, freshwater, Maranhão state, Neotropical region, Rio Mearim, Rio Munim, Rio Turiaçu, taxonomy


Figure 1. Charax awa: (A) Holotype, CICCAA 00752, 101.33 mm SL; Brazil, Maranhão, Alto Alegre do Pindaré, Pindaré river drainage, Mearim river basin. (Photographed by Beldo Ferreira). (B) Live specimen, paratype, CICCA00898, 62.2 mm SL; Brazil, Maranhão, Miranda do Norte, stream at the Miranda do Norte, Mearim river basin. (Photographed by Erick Guimarães).



Charax awa sp. n.

Charax gibbosus [non Charax gibbosus (Linnaeus, 1758)]: Martins and Oliveira 2011: 196-197.
Charax sp. - Martins and Oliveira 2011:196–197.

Diagnosis: Charax awa sp. n. can be distinguished from C. apurensis Lucena, 1987, C. condei (Géry & Knöppel, 1976), C. delimai Menezes & Lucena, 2014, C. gibbosus (Linnaeus, 1758), C. hemigrammus (Eigenmann, 1912), C. leticiae Lucena, 1987, C. macrolepis (Kner, 1858), C. metae Eigenmann, 1922, C. michaeli Lucena, 1989, C. niger Lucena, 1989, C. pauciradiatus (Günther, 1864), C. stenopterus (Cope, 1894) C. tectifer (Cope, 1870) by the orbital diameter (22.1–28.5% HL vs. 29.6–38.4% HL combined) (Fig. 2). Charax awa sp. n. differs from C. caudimaculatus Lucena, 1987 by the possession of a longer snout (snout length 23.3–32.8% HL vs. 20.3–22.8% HL); from C. notulatus Lucena, 1987 by the number of scales around the caudal peduncle (15–18 vs. 20–22) and by having more vertebrae (35 vs. 32). Furthermore, Charax awa sp. n. can be distinguished from C. condei, C. hemigrammus and C. stenopterus by having the lateral line complete (vs. incomplete); from C. delimai, C. metae and C. tectifer by having a toothless ectopterygoid (vs. presence of teeth on ectopterygoid) and having the anal-fin origin always anterior to the vertical through the dorsal-fin origin (vs. anal-fin origin on, or slightly posterior to the vertical through the dorsal-fin origin); from C. condei, C. delimai, C. hemigrammus, C. metae, C. pauciradiatus and C. stenopterus by the number of scale rows from the pelvic-fin origin to the lateral line (11–12 vs. 6–10 combined); from C. pauciradiatus by having more scale rows from the dorsal-fin origin to the lateral line (15–18 vs. 13–14). It can be distinguished from C. niger by having 8–10 transverse scale rows in space from the humeral spot to the supracleithrum (vs. 5–6); from C. condei, C. delimai, C. metae, C. rupununi Eigenmann, 1912 by the number of scale rows around the caudal peduncle (15–18 in C. awa sp. n. vs. 12–14 combined in C. condei and C. rupununi, 19–21 combined in C. delimai and C. metae). Finally, it differs from C. leticiae by having the maxilla extending to a vertical line posterior to pupil, near the posterior orbital margin (vs. maxilla extending slightly beyond vertical through middle of pupil) and from humeral spot distance (35.8–38.0 % SL vs. 39.0–44.0 % SL).

Distribution: Charax awa is known from the Rio Mearim, Rio Munim and Rio Turiaçu basins, Maranhão state, northeastern Brazil.

Etymology: The specific epithet honors the term Awá, from Tupi-guarani, meaning “man, people, person”, used by the native tribe Guajá, from the Maranhão state, for their self-denomination.


 Erick Cristofore Guimarães, Pâmella Silva De Brito, Beldo Rywllon Abreu Ferreira and Felipe Polivanov Ottoni. 2018. A New Species of Charax (Ostariophysi, Characiformes, Characidae) from northeastern Brazil.  Zoosystematics and Evolution. 94(1): 83-93.  DOI: 10.3897/zse.94.22106

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