Development of enzymes during ontogeny of two freshwater Decapoda: Aegla uruguayana (Aeglidae) and Macrobrachium borellii (Palaemonidae)

Abstract

The similarities or differences among species of the same family or among different families suggest a relationship with their feeding habits or a preference for the varios types of food. The aim of this study is to identify the presence of digestive enzymes lipases, total protease, amylases and cellulose, and the effects of sex and size in these activities in two decapod freshwater crustaceans. Specimens of different sizes and sexes of A. uruguayana and M. borellii were collected in the natural environment. In laboratory, enzymatic preparation consisted in homogenizing the digestive gland in a buffer Tris-HCl. The homogenates were centrifuged and the lipid layer was removed. Enzyme activities were determined by standard protocols. There were no statistically significant differences between sexes in any of the species under study. However, there were changes in the activity of amylases during the ontogeny of A. uruguayana, indicating that in juveniles the values of said activity are significantly higher than in the rest of the groups. M. borellii showed ontogenetic differences in total proteinase activity: organisms of range 2 (intermediate sizes) presented enzymatic activities much smaller than organisms of range 4 (larger sizes). The comparisons of enzymatic activities between both species yielded significant differences, being higher the values in the species A. uruguayana with respect to M. borellii. The results obtained in this work indicate that although both species are omnivorous and consume similar items, the activity of these digestive enzymes could be evidence of different strategies of utilization of the resource.