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

Three species of armored catfish of the genus Loricariichthys were clearly discriminated by starch gel isozyme electrophoresis on heart, liver and mus cle tissues. We scored 21 enzyme loci from 14 isozyme systems (ACP, ADH, AA T, EST, GCDH, G3PDH, G6PDH, GPI, ICDH, LDH, MDH, MDHP, PGM and SOD). Expect ed mean heterozygosity (H-e) ranged from 0.023 in Loricariichthys anus to 0 .050 in L. platymetopon and 0.035 in Loricariichthys sp. The percentage of polymorphic loci (P-0.99) was 14.3% for the three analyzed species. Nei's g enetic identity (I) was found to be 0.663 between Lorica riichthys anus and Loricariichthys sp., 0.329 between L. anus and L. metopon, and 0.478 betwe en L. platymetopon and Loricariichthys sp. Genetic variability, tissue spec ific differences, as well as applicability of isozyme electrophoresis as a tool for neotropical fish systematists are discussed.