Microglanis cottoides ( Boulenger , 1891 ) ( Siluriformes : Pseudopimelodidae ) : Distribution extension to Salí-Dulce River basin , northwestern Argentina

Microglanis cottoides (Boulenger 1891) is a known Paraná-Plata River basin catfish. Its geographic distribution is herein extended to a new drainage system, the Salí-Dulce River system, northwestern Argentina, which is a separate drainage from the Paraná-Plata basin. 1 CONICET e IBIGEO, Instituto de Bio y Geociencias Museo Ciencias Naturales de Salta. Mendoza 2, 4400 Salta, Argentina. 2 Instituto Miguel Lillo. Miguel Lillo 251, 4000 Tucumán, Argentina. 3 IBIGEO, Instituto de Bio y Geociencias Museo Ciencias Naturales de Salta. Mendoza 2, 4400 Salta, Argentina. * Corresponding author: E-mail: luis1813@yahoo.com Luis Fernández 1,2* and Gladys Gonzo 3 Microglanis cottoides (Boulenger, 1891) (Siluriformes: Pseudopimelodidae): Distribution extension to Salí-Dulce River basin, northwestern Argentina The Neotropical genus Microglanis Eigenmann, 1912, included in the family Pseudopimelodidae, comprises 21 species (Ruiz and Shibatta 2011). Microglanis is basically a miniature Pseudopimelodus, from which the former can be distinguished mostly on the basis of the shape of the band of premaxillary teeth, the reduction of the posterior portion of the lateral line, and its small body size (Mees 1974; 1978, Mori and Shibatta 2006). Microglanis has a relatively small body size 20 mm SL (M. zonatus Eigenmann and Allen 1942), and its largest species, M. parahybae (Steindachner 1880), reaching a maximum length of about 80 mm SL (Ruiz and Shibatta 2011). Microglanis presents the widest distribution among pseudopimelodids, ranging from the western slope of the Andes in Perú to the la Plata River basin in Argentina (Shibatta 2003). Among its species, Microglanis cottoides (Boulenger 1891) has been recorded for Argentina from the Paraná-Plata basin, Bolivia, Perú and Brazil (Ringuelet et al. 1967; Gonzo 2003; Shibatta 2003; Liotta et al. 2002; Liotta 2006). In September 2006, we collected a specimen we identified as M. cottoides (Figure 1) from the Río Romano (65°29’ W, 27°09’ S), Tucumán province, 260 m above sea level (Figure 2), a tributary of the Río SalíDulce basin. This new record for M. cottoides broadens the known geographic distribution of the species (Figure 2). It is also the first record of any species of the genus Microglanis for the Salí-Dulce River drainage, which increases the number of recorded fish species in the basin to sixty-eight. According to the biogeographical scheme of Ringuelet (1975), Liotta (2006), López et al. (2008), the Salí-Dulce drainage, a separated drainage from the ParanáPlata basin, is located within the Pampean Province. Following Bertaco and Cardoso (2005) the specimen from the Río Romano was identified as Microglanis cottoides (Table 1) based on the following distinguishing characters: premaxillary band teeth with no backwardly projecting lateral edges; laterosensory canal with 10 pores on anteriormost portion, with single terminal pore opening at vertical line slightly posterior to dorsal fin; head large, heavy, and flattened, as wide as long; cranium covered by skin; frontal fontanel slightly extended beyond eyes; minute occipital fontanel present; occipital crest small; eyes without free orbital margins; dorsal and pectoral fin spines well developed, dorsal spine with posterior edges serrated; caudal fin crossed by broad white band near middle; maxillary barbel long, extending beyond pectoral fin origin; dorsum with transverse black band; pectoral, pelvic, and anal fins with scattered chromatophores. The specimen was caught in dark water, shallow stream with sand, gravel, and woody debris (Figure 3). Microglanis is omnivorous and nocturnal, hiding during the day in rocky caves, under driftwood, or buried in the Figure 1. Microglanis cottoides, MCN 1514, 41.9 SL mm, Romano River at the intersection with Provincial route 380, Tucumán Province, Argentina.

The Neotropical genus Microglanis Eigenmann, 1912, included in the family Pseudopimelodidae, comprises 21 species (Ruiz and Shibatta 2011).Microglanis is basically a miniature Pseudopimelodus, from which the former can be distinguished mostly on the basis of the shape of the band of premaxillary teeth, the reduction of the posterior portion of the lateral line, and its small body size (Mees 1974;1978, Mori andShibatta 2006).Microglanis has a relatively small body size 20 mm SL (M.zonatus Eigenmann and Allen 1942), and its largest species, M. parahybae (Steindachner 1880), reaching a maximum length of about 80 mm SL (Ruiz and Shibatta 2011).
Microglanis presents the widest distribution among pseudopimelodids, ranging from the western slope of the Andes in Perú to the la Plata River basin in Argentina (Shibatta 2003).Among its species, Microglanis cottoides (Boulenger 1891) has been recorded for Argentina from the Paraná-Plata basin, Bolivia, Perú and Brazil (Ringuelet et al. 1967;Gonzo 2003;Shibatta 2003;Liotta et al. 2002;Liotta 2006).In September 2006, we collected a specimen we identified as M. cottoides (Figure 1) from the Río Romano (65°29' W, 27°09' S), Tucumán province, 260 m above sea level (Figure 2), a tributary of the Río Salí-Dulce basin.This new record for M. cottoides broadens the known geographic distribution of the species (Figure 2).It is also the first record of any species of the genus Microglanis for the Salí-Dulce River drainage, which increases the number of recorded fish species in the basin to sixty-eight.According to the biogeographical scheme of Ringuelet (1975), Liotta (2006), López et al. (2008), the Salí-Dulce drainage, a separated drainage from the Paraná-Plata basin, is located within the Pampean Province.
Following Bertaco and Cardoso (2005) the specimen from the Río Romano was identified as Microglanis cottoides (Table 1) based on the following distinguishing characters: premaxillary band teeth with no backwardly projecting lateral edges; laterosensory canal with 10 pores on anteriormost portion, with single terminal pore opening at vertical line slightly posterior to dorsal fin; head large, heavy, and flattened, as wide as long; cranium covered by skin; frontal fontanel slightly extended beyond eyes; minute occipital fontanel present; occipital crest small; eyes without free orbital margins; dorsal and pectoral fin spines well developed, dorsal spine with posterior edges serrated; caudal fin crossed by broad white band near middle; maxillary barbel long, extending beyond pectoral fin origin; dorsum with transverse black band; pectoral, pelvic, and anal fins with scattered chromatophores.
The specimen was caught in dark water, shallow stream with sand, gravel, and woody debris (Figure 3).Microglanis is omnivorous and nocturnal, hiding during the day in rocky caves, under driftwood, or buried in the    sand, and becoming more active at evening time or at night (Shibatta 2003;Bertaco and Cardoso 2005).The examined specimen is deposited at the Museo de Ciencias Naturales de Salta, Argentina (MCN 1514).We also examined comparative material of Microglanis from the fish collection of the museum (MCN 015,134,378,861).Measurements to the nearest 0.01 mm were made using a digital caliper following Bertaco and Cardoso (2005), Malabarba and Mahler Jr. (1998), and Mori and Shibatta (2006).

Table 1 .
Morphometric and meristic data for Microglanis cottoides MCN 1514, collected in Salí-Dulce River basin, Tucumán Province, Argentina.Standard length is expressed in millimeters; measurements 1-15 are percent of standard length; 16-22 are percent of head length.