Allozyme discrimination of three species of Loricariichthys (Siluriformes: Loricariidae) from Southern Brazil

Abstract

number of forms in each taxonomic group and to the great similarity found among species of the same genus. The family Loricariidae is the largest among the Siluriformes, with many species difficult to identify in several genera. In Loricariichthys Bleeker, 1862 as is usually the case for fish systematics and taxonomy, morphological characters forms the bulk of data used in descriptions as well as in species diagnoses (Reis & Pereira, in press). The genus Loricariichthys comprises 16 valid species (Isbriicker, 1980) and do not diverge from other neotropical taxa of fishes in regard to the gaps in the systematic knowledge. Thus, we search auxiliary tools for the morphological criteria. Different cytogenetic, biochemical and molecular techniques have been developed and used to assist in the diagnosis and species identification. As suggested by Thorpe & Sol-Cava (1994), isozyme electrophoresis can become an extremely useful tool when combined with morphological methods for the discrimination of closely related species. In this work we examine the level of genetic identity and variability among three species of Loricariichthys through allozyme electrophoresis, assaying loci and tissue expression. These are first and partial results from an attempt of the first author to form a bulk of allozyme data of some Loricariidae catfishes from southern Brazil, with the objective of finding genetic markers that could help to resolve questions on the systematics of this family. We also aim to corroborate the use of allozyme electrophoresis as a tool for the discrimination of morphologically similar species of Loricariidae.