Sunday, June 25, 2017

[Ichthyology • 2017] Trichomycterus ytororo • Living in the Waterfalls: A New Species of Trichomycterus (Siluriformes: Trichomycteridae) from Tabay Stream, Misiones, Argentina


Trichomycterus ytororo
Terán, Ferrer, Benitez, Alonso, Aguilera & Mirande, 2017

live specimens (A). holotype CI–FML 7241, 94.2 mm. (B–D). paratype CI–FML 7241, 60.9 mm SL.
Argentina, Misiones, Jardín América, Tabay stream, Paraná River basin. 


Abstract

A new species assigned to the genus Trichomycterus from the area of the waterfalls of Tabay stream, Paraná River basin, Misiones, Argentina, is described. Trichomycterus ytororo sp. nov. is distinguished from all other species in the genus by the presence of 31–35 dorsal procurrent caudal-fin rays and the combination of some external characters such as: coloration, number of pectoral–fin rays and pores of the laterosensory canals. The new taxon belongs to a presumably monophyletic group of species composed of T. crassicaudatus, T. igobi, and T. stawiarski based on the presence of 24 or more thickly ossified and rigid procurrent caudal-fin rays with a slender distal tip extending along the tips of at least ten neural spines.

Fig 4. Geographic distribution of the species assigned to the Trichomycterus stawiarski group: T. crassicaudatus (green symbols), T. igobi (white symbols), T. stawiarski (yellow symbols) and T. ytororo (red symbol). Stars represent the type localities. Some triangles symbols represent more than one collection locality. Numbers 1, 2, 3 indicate the Paraguay, Paraná and Iguazú Rivers, respectively.

Fig 5. Type locality of Trichomycterus ytororo; Tabay waterfalls, Tabay stream, Jardín América, Misiones, Argentina.

Ecological notes: The Tabay stream basin through 192 km from its headwaters at Campo Viera to its mouth on the Paraná River, at Jardín América (Fig 4). The stream bed is mainly composed of basaltic bedrock, in which sections with waterfalls and pools alternates all along its run. At the type locality (Tabay waterfall; Fig 5), the stream is surrounded by remnants of the Paranaense riparian forest, with its left margin degraded due to a camping site. This waterfall consists of three consecutive falls, the main one is 10m high and 20–50m wide, which drains into a narrow gorge. All specimens of Trichomycterus ytororo were captured above the waterfalls at shallow areas (about 1 meter depth or less) or in rapids witha predominantly rocky bottom and strong current. Trichomycterus davisi was the single congener recorded at the type locality, which was not collected syntopically with T. ytororo.

 Distribution: Trichomycterus ytororo is so far known only from its type locality, the Tabay waterfalls in the Tabay stream (Fig 5), a tributary of the left bank of the Paraná River, province of Misiones, northeast of Argentina (Fig 4).

Etymology: The specific epithet ytororo derived from the indigenous language Guaraní (“ytororõ”) which means “waterfall” in reference to the habitat occupied by the new species. A noun in apposition.


Guillermo Enrique Terán, Juliano Ferrer, Mauricio Benitez, Felipe Alonso, Gastón Aguilera and Juan Marcos Mirande. 2017. Living in the Waterfalls: A New Species of Trichomycterus (Siluriformes: Trichomycteridae) from Tabay Stream, Misiones, Argentina.
 PLoS ONE. 12(6); e0179594.  DOI: 10.1371/journal.pone.0179594

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