Proteolytic enzymatic activities in the omnivorous R. quelen and P. maculatus and detritivorous L. anus and H. commersoni in the summer and winter: (5) pepsin in the stomach; (6) trypsin in the anterior intestine; (7) trypsin in the posterior intestine; (8) chymotrypsin in the anterior intestine; (9) chymotrypsin in the posterior intestine. Different letters indicate significant differences between species in the same season. * Indicates a significant difference from summer in the same segment (p < 0.05). (U, a Caraway unit) (n = 15 from each species at each season).