Trichomycterus alterus ( Marini , Nichols & La Monte , 1933 ) and T . corduvensis Weyenberg 1877 ( Siluriformes : Trichomycteridae ) : new records from the High Andean Plateau

New records of two Trichomycterus species are herein added to the existing checklist of catfishes living at elevations above 3,000 m in the Andes of South America. Trichomycterus alterus and T. corduvensis are recorded at 3,430 m above sea level from the High Andean Plateau (or Puna) in a stream near Antofagasta de la Sierra, Provincia de Catamarca, Argentina. Morphometric and meristic data of examined specimens are included.

The Andean ichthyofauna is miniscule (around 375 spp.) compared to that of the South American lowlands (6,000+ spp.) (Schaefer 2011;Fernandez & Vari 2012;Reis et al. 2016).The depauparate ichthyofauna from above 3,000 m in the Andes consists mainly of 34 species of Trichomycteridae, 22 of which occur on the High Andean Plateau or Puna (Arraya et al. 2009;Fernandez 2013).The Puna of the Central Andes is the second largest and highest plateau on the Earth after the Tibet Plateau.It is the prominent feature that characterizes the Andean mountain range along the western border of South America (Aramayo et al. 2017).The high-elevation Puna Plateau extends from southwestern Peru through western Bolivia and into Chile and northern Argentina; it has a relatively long dry season (Ramos 1999;Risse et al. 2013;Becker et al. 2015).The Puna includes endorrheic drainage such as lakes Titicaca and Poopó, and numerous small high-altitude freshwater lakes and swamps, as well as extensive salars such as Coipasa-Uyuni in Bolivia and Antofalla, Hombre Muerto, and Salinas Grandes in Argentina (Kraemer 1999;Schaefer 2011;Ducea et al. 2013;Fernandez 2013).
The ichthyological collection of Facultad Ciencias Exactas y Naturales, Universidad Nacional de Catamarca, Catamarca, Argentina (FACEN) was revised.Six specimens of Trichomycterus alterus and eight of T. corduvensis were identified based on comparisons with type material (for Trichomycterus alterus; type material of T. corduvensis is missing), the original descriptions, and additional specimens listed below.Measurements to the nearest 0.01 mm were made using a digital caliper following Tchernavin (1944) and Fernandez & Vari (2012).Institutional acronyms follow Sabaj Pérez (2016).In examined material, the number     The specimens of T. alterus (Figure 1A) were recognized by the following combination of characters: caudal peduncle narrow and laterally compressed; dorsal-fin origin unpigmented (Figure 4A); interopercular and opercular odontodes embedded in a thick integument; premaxilla with 2 or 3 rows of teeth; 12 principal caudal-fin rays and distal margin concave; maxillary barbel expanded basally; 6 to 9 branched dorsal-fin rays; 7 or 8 pectoral-fin rays, with small filament; 5 branched anal-fin rays (Fernandez & Vari 2002).Additional features include: supraorbital canal segment discontinuous, with pores s1, s2, s3, and s6 present and laterosensory canal of trunk with 3 pores anteriorly (LF pers.obs.).Morphometric and meristic data is presented in Table 1.
The T. corduvensis (Figure 1B) specimens were recognized by the following combination of characters: caudal peduncle smoothly continuous with dorsal and ventral profiles of trunk; papillae-like structures present on body; unpigmented region on the dorsal-fin origin absent (Figure 4B); interopercular and opercular odontodes not embedded in thick integument; premaxilla with 4 to 6 teeth rows and distal portions of teeth in each jaw flattened and slightly expanded; 13 principal caudal-fin rays with distal margin straight (Fernandez 2001).Additional features include: supraorbital canal segment continuous, with pores s1, s2 and s6 present and laterosensory canal of trunk with 4 to  Eye diameter 11.5-13.912.3 0.9 First pectoral-fin ray length 84.8-98.993.5 5.1
Trichomycterus alterus and T. corduvensis inhabit the Río de la Plata basin, in northwestern and central Argentina and the Amazonas basin, at western of Bolivia (Fernandez 2001;Fernandez & Vari 2002;Arraya et al. 2009) (Figure 5).However, they were not collected in high altitudes until now.Several genera of trichomycterid catfishes are endemic to the Andean Cordillera, such as Silvinichthys Arratia, 1998 (Argentina), Hatcheria Eigenmann, 1909 (Argentina and Chile), Rhizosomychthys (Miles, 1942) (Colombia), as well as many undescribed species of Trichomycterus Valenciennes, 1832 (Fernandez 2013;Fernandez et al. 2014;Reis et al. 2016).Trichomycterid catfishes are highly specialized for life in uplands along the Andean mountains, and they occur in a remarkable variety of environments, including temporary streams, subterranean drainages, high elevation streams, and warm thermal water (Fernandez & Vari 2012).They generally are equipped with opercular and interopercular odontodes that can be everted to provide friction when these fishes climb waterfalls (Zuanon & Sazima 2005;Fernandez 2013).Although some Trichomycterus species can occur at altitudes up to about 4,800 m (T.roigi Arratia & Menu-Marque, 1984), they become scarce at high elevations (Fernandez 2013).

Figure 5 .
Figure 5. Map of Trichomycterus spp.modified from Liotta (2006).A. Trichomycterus alterus and B. T. corduvensis.All localities (circle) are below 2,500 m and 1,500 m above sea level, respectively.The new record (asterisk) is at 3,430 m above sea level in Antofagasta de la Sierra.