Whiteleg shrimp (Litopenaeus vannamei, Boone, 1931) isotrypsins: Their genotype and modulation

Based on information about isotrypsins found by substrate-SDS-PAGE in the whiteleg shrimp Litopenaeus vannamei and their segregation, an explanation for the presence of three-trypsin phenotype was sought. Isotrypsins A, B, and C depend on two loci: locus β, which is homozygous, yielding isoenzyme C, and locus α, which is heterozygous, yielding isoenzymes A and B. Segregation in locus α in offsprings from 20 families was analyzed. Results demonstrated that isotrypsins were segregated according to Mendelian rules, and hence, external stimuli did not affect the phenotype. To corroborate this, the phenotype was evaluated in relation to changes in trypsin activity during a digestion process. Trypsin phenotypes found in shrimp feces were also analyzed. Results showed that phenotypes were conserved by individuals. Therefore, changes in trypsin activity found in previous investigations must be related to changes in the concentration of the established isotrypsins.