Abstract
Trichomycterus dali, new species, is described from flooded limestone caves in Serra da Bodoquena karst area, State of Mato Grosso do Sul, Central Brazil. The new species is diagnosed by a unique character in the genus, the presence of conspicuous, ridge-like adipose folds lining dorsally throughout the body. Trichomycterus dali can be further distinguished readily from epigean congeners by the reduction of eyes and skin pigmentation (except for T. gorgona), and from remaining congeners (i.e., all hypogean plus T. gorgona) by the total loss of eyes, not visible externally (except for T. sandovali and T. spelaeus). Other diagnostic features includes very long barbels, especially the nasal (99.3-143.5% HL) and the maxillary (97.0-131.3% HL), pectoral-fin ray count reaching I,9 and a unique cranial fontanel with a conspicuous constriction on the meeting point of supraoccipital and the two frontal bones. The troglobitic status of the species is suggested by the presence of troglomorphisms on an advanced degree, especially the reduction of skin pigmentation, the total loss of eyes and the enlarged barbels. In addition, the presence of a well developed adipose fold in adults may indicate a distinctive adaptation acquired by neoteny to withstand the food scarce conditions of its hypogean habitat.
Highlights
Brazil has one of the most remarkable subterranean ichthyofaunas in the world, comparable to few other countries or geographically comparable karst areas, such as Mexico, China and southeastern Asia (Bichuette & Trajano, 2008; Trajano et al, 2009; Trajano & Bichuette, 2010)
All but two species of Brazilian troglomorphic fishes are siluriforms which belong to four families: Callichthyidae, Loricariidae, Heptapteridae and Trichomycteridae, the two latter being the most species-rich (Trajano & Bichuette, 2010)
Trichomycterids are among the most successful fishes colonizing subterranean habitats (Castellanos-Morales, 2008), and up to now there are 13 nominal species in the genera Silvinichthys, Glaphyropoma, Ituglanis and Trichomycterus (Proudlove, 2010). The latter includes the majority of described troglomorphic species: T. chaberti Durand, from Bolivia, T. spelaeus DoNascimiento, Villarreal e Provenzano, from Venezuela, T. sandovali Ardila-Rodriguez, T. santanderensis Castellanos-Morales and T. uisae Castellanos-Morales, from Colombia, and T. itacarambiensis Trajano e de Pinna, from eastern Brazil
Summary
Brazil has one of the most remarkable subterranean ichthyofaunas in the world, comparable to few other countries or geographically comparable karst areas, such as Mexico, China and southeastern Asia (Bichuette & Trajano, 2008; Trajano et al, 2009; Trajano & Bichuette, 2010). Trichomycterids are among the most successful fishes colonizing subterranean habitats (Castellanos-Morales, 2008), and up to now there are 13 nominal species in the genera Silvinichthys, Glaphyropoma, Ituglanis and Trichomycterus (Proudlove, 2010) The latter includes the majority of described troglomorphic species: T. chaberti Durand, from Bolivia, T. spelaeus DoNascimiento, Villarreal e Provenzano, from Venezuela, T. sandovali Ardila-Rodriguez, T. santanderensis Castellanos-Morales and T. uisae Castellanos-Morales, from Colombia, and T. itacarambiensis Trajano e de Pinna, from eastern Brazil. The rio Miranda lowlands (Alvarenga et al, 1982), which includes the “Zona Serrana Oriental” (Eastern Highland Zone - Almeida, 1965), constitutes a vast lowland area (elevation of 100-350 m), bordered to the east by the Maracaju-Campo Grande Plateau In both Bodoquena Plateau and rio Miranda lowlands, the landscape is influenced by the presence of Corumbá Group carbonate rocks, which give rise to karstic surface relief with many caves, dolines and other typical features. The vegetation can be characterized as a remnant of Atlantic forest in transition to Cerrado
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