In population studies based on genetic-biochemical markers, variations induced by ontogenetic development, sex and gonad maturation act as a potencial source of bias. These aspects were analysed for patterns of eye-lens proteins of Micropogonias furnieri (Sciaenidae), following electrophoregrams obtained from 546 specimens ranging from 98 and 710 mm in length, collected along the southeastern Brazilian coast (23º S - 29º21'S). Proteins were extracted in 0.9% NaCl solution, processed on cellulose acetate membranes in a bridge buffer discontinuous system trisglicine-barbital, for 25 minutes at 300 V, and stained with Ponceau S. The basic pattern obtained was divided into 4 sets and 8 fractions, that were evaluated by scanning in a ATAGO-QUICK densitometer. No differences were found in the patterns of right and left eye-lens, male and female and maturity stages for the same length class. Patterns variations related to ontogenetic development were found: set I present a decrease, while sets II, III and IV show an increase in their relative concentration. Set II showed two fractions for young (until 300-350 mm) and only one for adults. Fractions I, II-1, II-2, III-3 become stable above 300-350 mm and I and IV-2 above 450-500 mm length. For the utilization of this genetic-biochemical markers and according to the study purpose the comparison of fractions or patterns should consider: a - only fractions whose relative concentration were stable (III-1, III-2 and IV-1) or, b - only electrophoregrams from fishes of narrow total length range, whithout ontogenetic influence or, c - only patterns of individuals with total length above of which the fractions concentration become stable (II-2 and III-3 above 300 mm and/or I and IV-2 above 450 mm) or, d - only the basic patterns of the adults, when fractions number and relative concentration become stable. This last alternative (d) seems to be more appropriate either in interspecific studies when the aim is restricted to spacial populations delimitation, or in taxonomic studies, when there are no problems concerning to the classification of young forms.
Micropogonias furnieri; Sciaenidae; Electrophoresis; Eye-lens; Proteins; Ontogenetic variation; Southeastern coast