Saturday, April 3, 2021

[Ichthyology • 2021] Redescription of the Guiana Shield Darter Species Characidium crandellii and C. declivirostre (Characiformes: Crenuchidae) with Descriptions of Two New Species: Characidium duplicatum & C. wangyapoik

Characidium crandellii Steindachner, 1915; C. declivirostre Steindachner, 1915; 

Characidium duplicatum C. wangyapoik 
 Armbruster, Lujan & Bloom, 2021

Based on collections made in the western Guiana Shield over the last 21 years, Characidium crandellii and C. declivirostre are redescribed and two similar species are described from Guyana. These species all have enlarged paired fins with three to four rays thickened ventrally on the pectoral fin and two rays thickened on the pelvic fin. The species can be separated from all other Characidium and Melanocharacidium by having the venter unscaled from the isthmus to the pelvic origin. Characidium crandellii is found in the Essequibo and Takutu River systems and in an isolated population above Tencua Falls in the Ventuari River and the upper Paragua River (Orinoco River basin). Characidium declivirostre is found throughout the right-bank, shield tributaries of the Orinoco River system and in the upper Negro River. Characidium duplicatum, new species, appears to be rare but widely distributed in the Essequibo River system. Characidium wangyapoik, new species, is only known from the upper Ireng River, Branco River basin, along the border between Brazil and Guyana.

Characidium crandellii Steindachner, 1915

Characidium declivirostre Steindachner, 1915

Characidium duplicatum, new species

Distribution.—(Fig. 9) Found throughout the Essequibo River basin, but has been rarely encountered during our surveys. Most locations are in the lower Potaro and Kuribrong, but two localities are in the upper Essequibo upstream of the mouth of the Kuyuwini River.

Etymology.—Duplicatum is Latin for double and is a neuter adjective. In reference to the presence of two unbranched anal-fin rays.


Characidium wangyapoik, new species

Distribution.—(Fig. 9) Characidium wangyapoik is only known from the upper Ireng River basin (Amazon River) along the Brazil/Guyana border (known as the Rio Mau in Brazil). Specimens were collected from below Orinduik Falls to the upper falls on the Ireng and its equal tributary, the Sukwabi River, but not above the Uluk Tuwuk or Wotawanda falls of the upper Ireng and Sukwabi Rivers (see Lujan et al., 2020, for a more detailed map and description of this area).

Etymology.—Wangyapoik is the Patamona word for the species, and it is used as a noun in apposition. Wang means ‘honey' and yapoik means ‘seated,’ perhaps in reference to the yellowish color. The Patamona also refer to the species by the English common name of “fallsfish.”

Jonathan W. Armbruster, Nathan K. Lujan and Devin D. Bloom. 2021. Redescription of the Guiana Shield Darter Species Characidium crandellii and C. declivirostre (Crenuchidae) with Descriptions of Two New Species. Ichthyology & Herpetology. 109(1); 102-122. DOI: 10.1643/i2019299