Monday, June 28, 2021

[Ichthyology • 2021] Corydoras bethanae • A New Arc-striped Species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the Peruvian Amazon

A. Corydoras bethanae, female holotype, río Blanco, Department of Loreto, Peru.
B. Corydoras arcuatus unpreserved aquarium specimen.
Bentley, Grant & Tencatt, 2021
Photos by Steven Grant & Hans-Georg Evers.

A new Corydoras is described from the Blanco and Ucayali river basins in Peru. The new species can be distinguished from its congeners by having the following features: (I) posterior margin of dorsal-fin spine with laminar serrations directed towards the origin of the spine; (II) a long, wide, arched, and continuous black stripe, which runs parallel to the dorsal profile of the body, extending at least from the region below anterior origin of dorsal fin to the anterior half of the ventral caudal-fin lobe; (III) a black stripe transversally crossing the eye, forming the typical mask-like blotch; mask clearly not fused to arched stripe in most specimens; some specimens with mask separated from arched stripe by a thin line around the suture between neurocranium (in the region composed by the posteroventral margin of parieto-supraoccipital plus the posterodorsal margin of the compound pterotic) and first dorsolateral body plate; (IV) posterior margin of pectoral-fin spine with laminar serrations directed towards the origin of the spine; (V) pointed snout, presenting a long mesethmoid, with anterior tip larger than 50% of the entire length of the bone; and (V) ventral surface of trunk covered by small, non-coalescent platelets. A discussion on the possible positive adaptive value of the arc-striped color pattern is also provided.

Keywords: Pisces, Aposematism, Corydoradinae, mimicry, río Blanco, taxonomy

FIGURE 2. A. Corydoras bethanae, holotype alive, MUSM 69403, female, 51.2 mm SL, Peru, Department of Loreto, río Blanco. B. Corydoras arcuatus unpreserved aquarium specimen. C. Corydoras granti unpreserved aquarium specimen from Peru, río Tapiche.
Photos A and C by Steven Grant, B by Hans-Georg Evers.

FIGURE 6. Live coloration of paratypes of Corydoras bethanae, BMNH 2017.5.25.1-21, showing A. female, and B. male. Fin coloration affected by background colors. Arrows indicate gap in arc-stripe around the suture between neurocranium.
Photos by Steven Grant.

FIGURE 8. Photos of the habitat of Corydoras bethanae, new species, showing A. its type-locality, the río Blanco, and B. the confluence of río Blanco (left) with río Tapiche, both in Peru.
Photo A by Mark Breeze, and B by Tom Christoffersen.

Rebecca Frances Bentley, Steven Grant and Luiz Fernando Caserta Tencatt. 2021. A New Arc-striped Species of Corydoras Lacépède, 1803 (Teleostei: Callichthyidae) from the Peruvian Amazon. Zootaxa. 4948(2); 184–200. DOI: 10.11646/zootaxa.4948.2.2