Journal of Fish Biology (2007) 71, 1303–1316 doi:10.1111/j.1095-8649.2007.01589.x, available online at http://www.blackwell-synergy.com A catfish of the genus Trichomycterus from a thermal stream in southern South America (Teleostei, Siluriformes, Trichomycteridae), with comments on relationships within the genus L. FERNA´ NDEZ*† AND G. MIRANDA‡ *Departamento Vertebrados, Instituto Miguel Lillo, Miguel Lillo 251, 4000 Tucuman,´ Argentina and ‡Instituto de Ecologı´a, Universidad Mayor de San Andres, Bolivia, CP 10077, La Paz, Bolivia (Received 16 June 2005, Accepted 23 May 2007) The first record of two trichomycterid species from the thermal waters of a small stream in Miraflores, north of Potosı´ , Bolivia is given. The reported species are Trichomycterus therma n. sp. and Trichomycterus tiraquae. The new species differ from all congeners in the possession of thickened transverse skin on the ventral surface of the head. They are further distinguished from all congeners by the following combination of characteristics: presence of spatulate incisiform premaxillary teeth; presence of large and rounded papilla-like structures on trunk of body; continuous segment of the laterosensory canal within the frontal with the presence of a segment between pores 2 and 6; long laterosensory canal with four to six pores; maxilla with a short anterior process that is smaller than the main axis of the bone, and has an anterior orientation; mesethmoid shaft narrower than the width of the lateral cornua; prepelvic length 58 7–61 0% of Á Á standard length (L ); head width 19 1–22 8% of L ; submaxillary barbel length 23 9–37 5% of S Á Á S Á Á head length (LH). Two derived characters, namely the presence of spatulate incisiform premaxillary teeth and large and rounded papilla-like structures, define a monophyletic group within Trichomycterus, comprising T. therma, T. corduvensis and T. tiraquae. # 2007 The Authors Journal compilation # 2007 The Fisheries Society of the British Isles Key words: Bolivia; catfishes; new species; thermal water. INTRODUCTION The genus Trichomycterus is the largest non-monophyletic assemblage in the Tri- chomycteridae, and its taxonomy requires a comprehensive revision (Fernan´ dez & Schaefer, 2005). Trichomycterus has >100 recognized species that inhabit a diver- sity of habitats from Amazonian lowlands to the Andean cordilleras (Arratia, 1998; de Pinna, 1998). Seven or eight species of Trichomycterus occur in the west- ern region of Bolivia (Eigenmann, 1918; Terrazas Urquidi, 1970; Arratia & Menu-Marque, 1984; Ferna´ ndez, 2000a, 2001; Ferna´ ndez & Osinaga, 2006). †Author to whom correspondence should be addressed at present address: Division of Vertebrate Zoology, Department of Ichthyology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192, U.S.A. Tel.: 1 212 769 5797; fax: 1 212 769 5642; þ þ email: [email protected] 1303 # 2007 The Authors Journal compilation # 2007 The Fisheries Society of the British Isles 1304 L . F E R N A´ N D E Z A N D G . M I R A N D A Trichomycterus shows a high potential for colonization of extreme environ- ments such as high altitude (>4000 m), subterranean streams, island fresh waters (56 km off the Colombian coast) and, as reported in this study, warm thermal waters (>35° C) (Pouilly & Miranda, 2003; Fernandez´ & Schaefer, 2005). The Andean and Preandean regions are characterized by the presence of several endorrheic drainage basins, each of which has evolved a characteristic fish fauna with some of them poorly known or hitherto inaccessible (Arratia & Menu-Marque, 1984; Fernandez´ & Vari, 2000, 2002; Fernandez´ & Schaefer, 2003). The environmental impacts of gold-mining activities in these regions include deforestation and the release of thousands of tonnes of sediment and chemicals into exploited rivers (e.g. >330 t of mercury released since 1952 according to Maurice-Bourgoin & Quiroga, 2002), and these impacts endanger many populations of endemic species of Trichomycterus. This study presents a description of a new species of Trichomycterus, found with Trichomycterus tiraquae (Fowler) in a thermal stream at the locality of Miraflores, near the city of Potosı´, in Bolivia. De Pinna & Wosiacki (2003) placed T. tiraquae in synonymy with Trichomycterus rivulatus Valenciennes but this is disputed (L. Fernan´ dez, pers. obs.). This study represents the first record of species of Trichomycteridae known to inhabit thermal waters. MATERIALS AND METHODS STUDY AREA Miraflores has a complex of thermal streams (19°279 S; 65°479 W) in Potosı´ Depart- ment, Bolivia. It lies in the ‘Ecoregion of the Vertiente Oriental, Valles interandinos: Prepuna’ (Gerold, 2003), within the Austral biogeographic region. The study area is characterized by a subtropical climate. The annual average air temperature ranges from 14 to 16° C and the annual average precipitation ranges from 100 to 400 mm (Gerold, 2003). The Potosı´ area is crossed by several parallel streams running eastwards to join the Rı´ o Tarapaya, a tributary of the Rı´ o Pilcomayo. The new species was col- lected in an unnamed thermal stream that originates from sub-Andean mountains and flows as a small watercourse 800 m in length with four waterfalls of 7 to 9 m height each. The fishes of interest occur 500 m downstream from the thermal source at a site where water temperature is 37° C. This contrasts with the Rı´ o Tarapaya, where the water temperature is 12 to 18° C. Fishes were collected using backpack electrofishing gear delivering a current between 300 and 600 V and quickly killed by stunning. Individuals were preserved in buffered formaldehyde (4%) before transport to the laboratory. Water temperature was mea- sured with a WTW digital thermometer and pH with a Hach apparatus. Measurements were taken on the left side of each specimen with digital callipers under a stereomicro- scope, and followed the methods of Tchernavin (1944) and de Pinna (1992). Cleared and double-stained osteological preparations (denoted C&S) of comparative material follow Taylor & Van Dyke (1985), and some type specimens were studied from radio- graphs. Osteological terminology follows Baskin (1973) and de Pinna (1989, 1998), and the numbering system and terminology for the laterosensory pores of the head follow Arratia & Huaquin (1995) and Arratia (1998). Counts of dorsal and anal-fin rays and vertebrae follow de Pinna (1992) with vertebral counts omitting the compound verte- brae of the Weberian complex and the vertebrae associated with the caudal skeleton. Counts of caudal vertebrae follow Fernand´ ez & Schaefer (2003). Institutional abbreviations follow Leviton et al. (1985), with the addition of FLBS, Flathead Lake Biological Station, Montana; IBA, Instituto de Biologı´ a Animal, Mendoza, Argentina; MFA-ZV, Museo Provincial de Ciencias Naturales Florentino Ameghino, Santa Fe, Argentina. # 2007 The Authors Journal compilation # 2007 The Fisheries Society of the British Isles, Journal of Fish Biology 2007, 71, 1303–1316 N E W S P E C I E S O F C A T F I S H F R O M T H E R M A L W A T E R S 1305 Comparative material examined in this study is that cited in Fernandez´ (2000b) and Fernan´ dez & Vari (2000, 2004) with the addition of specimens listed below. Trichomycterus aguarague Fernandez & Osinaga MNKP 4002, paratypes, six specimens (1 C&S), 28 7–56 1 mm standard length (LS), Bolivia, Tarija, Gran Chaco, Rio Caiguami, 9 MarchÁ 2003,Á coll. Osinaga, Coro. Trichomycterus alterus (Marini, Nichols & La Monte) FML 2085, nine specimens (C&S), 43 6–49 1 mm LS, Argentina, Catamarca, San Blas, Andalucas, 7 September 1994, coll. FernÁ a´ ndeÁz, Scrocchi, Montero; FML 2088, four speci- mens (2 C&S), 40 8–42 1 mm LS, Argentina, Catamarca, Paclı´n, Rı´o Paclı´n, 16 September 1994, coll. FernÁandez,´ Á Scrocchi, Montero. Trichomycterus barbouri (Eigenmann) CAS 64578, paratype, one specimen, 29 5 mm L , Bolivia, Rı´ o Beni, coll. Barbour; Á S USNM 120289, paratypes, four specimens, 27 8–29 7 mm LS, Bolivia, Alti Beni. Tricho- mycterus belensis Fernandez´ & Vari FML 2531,Á paratypes,Á 10 specimens (2 C&S), 25 5– Á 58 7 mm LS, Argentina, Catamarca, Belen, Laguna Blanca, 8 September 1993, coll. FernÁ andez,´ Scrocchi, Lavilla. Trichomycterus corduvensis Weyenbergh FML 1215, four specimens, 39 0–93 1 mm L , Argentina, Tucuman, Trancas, Rı´ o Vipos, 25 July 1985, Á Á S coll. Pagaburo; FML 1796, four specimens (2 C&S), 26 6–57 9 mm LS, Argentina, Tucuman, Yerba Buena, Rı´ o Muerto, 5 October 1992, coll.ÁFernandez,Á´ Scrocchi, Lobo. Trichomycterus chaberti Durand USNM 236426, two specimens, 64 2–83 8 mm LS, Bolivia, Potosı´ , Cave Toro Toro, 31 August 1982, coll. Morales. TrichomycterusÁ Á gorgona Fernandez & Schaefer ANSP 149946 holotype (radiographs), 63 6 mm LS, Colombia, Cauca, Isla Gorgona, 21 September 1961; ICN-MHN 10019 paratype,Á one specimen, 58 7 mm L , Colombia, Cauca, Isla Gorgona, 21 September 1961. Trichomycterus pseu- Á S dosilvinichthys Fernandez & Vari FML 2588, holotype, 61 1 mm LS, Argentina, La Rioja, Chilecito, Rı´ o Amarillo, 8 September 1994, coll. FernÁandez,´ Scrocchi, Montero; FML 2589, paratypes, nine specimens (C&S), 54 5–62 2 mm LS, Argentina, La Rioja, Chilecito, Rı´ o Amarillo, 8 September 1994, coll. FernÁ andez,´ Á Scrocchi, Montero. Tricho- mycterus punctulatus Valenciennes FMNH 58672, paratype, one specimen, 97 8 mm L , Á S Peru.´ T. rivulatus MNHNC 2347, two specimens, 86 9–90 1 mm LS, Chile, Parinacota, Arica, 30 Abr 1979, coll. Gallardo. T. tiraquae ANSPÁ 69127,Á paratypes, two specimens, 27 7–32 6 mm LS, Bolivia, Cochabamba, Tiraquae, 30 September 1937, coll. Carriker, Howes;Á ÁMUSM 15476, three specimens, 58 7–60.1 mm L , Bolivia, Potosı´ , Rı´ o Tupiza; Á S CBF uncat., two specimens, 38 7–49 9 mm LS, Bolivia, Potosı´, Rı´o Pilcomayo, 20 October 2001, coll.