Thursday, April 11, 2024

[Ichthyology • 2024] Cyphocharax orion • A New Species of Cyphocharax (Characiformes: Curimatidae) from the rio Juma, rio Aripuanã Basin, southern Amazon Basin

Cyphocharax orion
Melo & Faria, 2024

A new species of Cyphocharax is described from the rio Juma, which flows across the meridional Amazon basin and is a tributary of the rio Aripuanã in the rio Madeira fluvial system. Features distinguishing the new species from congeners include a longitudinally elongated caudal peduncle blotchextending from the vertical line through the adipose-fin terminus to the base of median caudal-fin rays, the number of scale series along the lateral line and between the lateral line and dorsal-fin origin, morphometric variation, and the patterns of pigmentation along the body. The species was discovered in a lesser-explored region and appears to be an endemic of the rio Aripuanã in the southern Amazon basin.

Keywords: Brazilian Shield, Characiformes, Cyphocharax spilurus clade, Madeira River, Ostariophysi.

Cyphocharax orion:
A. ZUEC 18036, paratype, 77.8 mm SL, formalin-fixed specimen;
B. LBP 33070, 57.9 mm SL, ethanol-fixed specimen;
rio Juma, rio Aripuanã, Apuí, Amazonas, Brazil.

Cyphocharax orion, new species

Diagnosis. Cyphocharax orion distinguishes from all congeners, except C. laticlavius Vari & Blackladge, 1996, C. modestus (Fernández-Yépez, 1948), C. naegelii (Steindachner, 1881), C. pantostictos Vari & Barriga Salazar, 1990, and C. sanctigabrielis, by having a horizontally elongated caudal-peduncle blotchof dark pigmentation running from the vertical line through the adipose-fin terminus to the base of median caudal-fin rays (vs. absence or blotch relatively small and confined to caudal-peduncle region). Cyphocharax orion differs from C. laticlavius by the absence of a midlateral dark stripe extending from midbase of dorsal fin to basal portions of middle caudal-fin rays (vs. presence), and head length 24.5–26.2% of SL (vs. 29.6­–34.3% of SL). Cyphocharax orion differs from C. modestus by having 4.5 scales from dorsal-fin origin to lateral line (vs. 5.5–7) and head length 24.5–26.2% of SL (vs. 27–31% of SL). Cyphocharax orion differs from C. naegelii by having 29 scales in lateral line (vs. 39­–45). The new species differs from C. pantostictos by the absence of dark spots over the center of scales on the lateral and dorsolateral region of the body (vs. presence) and distance from snout tip to anal-fin origin 77.5–81.3% of SL (vs. 83–85% of SL). Finally, C. orion differs from C. sanctigabrielis by having relatively thin and uniform caudal-peduncle blotch (vs. caudal-peduncle blotch thick and posteriorly wider), number of lateral-line scales 29 (vs. 31), distance between dorsal-fin origin and pelvic-fin origin 33.5­–37.9% of SL (vs. 30.9–33.0% of SL), distance between dorsal- and pectoral-fin origin 34.6–37.1% of SL (vs. 32.2–34.0% of SL), and postorbital length 39.8–43.2% of SL (vs. 33.1–39.0% of SL).

Etymology. The epithet orion derives from Ancient Greek Ὠρίων (Ōríōn) which means “heaven’s light”, or Arion, which means “warrior”. In ancient Greek mythology, Orion was a giant hunter who, after being killed by Scorpion sent by Earth mother Gaia, either Zeus or Artemis placed in the night sky as the constellation Orion. The Orion Constellation contains the Great Orion Nebula, one of the brightest nebulae in the visible sky, and the Orion’s Belt asterism formed by three bright blue supergiants: the triple star system Alnitak, the major star Alnilam, and the multiple star system Mintaka. The name Cyphocharax orion is in allusion to three major southern Amazonian rivers Madeira, Aripuanã (type-locality), and Tapajós, and symbolizes the resistance to anthropogenic pressures with strength, bravery, and universe brilliance. A noun in apposition.

Bruno F. Melo and Tiago C. Faria. 2024. Description of A New Species of Cyphocharax from the rio Juma, rio Aripuanã Basin, southern Amazon Basin (Teleostei: Curimatidae).  Neotrop Ichthyol. 22(1):e230122. DOI: 10.1590/1982-0224-2023-0122