Abstract
Samples from seven different locations of the genus Pimelodella were genetically examined, two caves (exclusively subterranean, upper Tocantins River and São Francisco River) and five epigean (from upper Paraná River basin). Cytogenetic analyses revealed the same diploid number (2n=46) for all species besides similarities in both number and location of nucleolar organizer regions and C bands. FISH with 5S rDNA probes and CMA3 staining indicated significant differences among the studied species. Application of PCR-RFLP in ATPase 6 and 8 mitochondrial genes allowed building a minimum evolution phenogram identifying the close evolutionary relationship among groups. Both chromosomal and molecular data were useful to infer the relationships among studied Pimelodella species.
Highlights
The neotropical region encompasses the richest and most diversified fish fauna in the world (Nelson, 2006)
The nucleolar organizer regions were identified by silver nitrate staining, as described by Howell & Black (1980), and chromomycin A3 staining was performed according to Schmid (1980)
Cytogenetic Analyses All studied species presented a diploid number of 2n = 46 and fundamental number (FN) = 92, but the chromosomal structure varied among species (Fig. 1 and Table 1)
Summary
The neotropical region encompasses the richest and most diversified fish fauna in the world (Nelson, 2006). Within the family Heptapteridae (Siluriformes), Pimelodella is the most specious genus, with more than 70 nominal species, among which at least 30 occur in Brazil (Bockmann & Guazzelli, 2003). These are small to medium sized catfishes (most with less than 15 mm SL, a few surpassing 20 mm SL), generalized in morphology and habits, living in a variety of habitats, from headwater streams to large rivers, in the epigean (surface) and subterranean environment.
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