Abstract
The enzymatic activities involved in the digestion of proteins and carbohydrates were compared among three organs of the digestive track of two Siluriformes fish species, and between two areas: a reservoir, and an area downriver of it. Our aim was to test the hypothesis that the digestive organs of species with varied feeding habits have different enzymatic activities, and that the enzymatic activity differs among seasons and environmental conditions. The iliophagous/herbivorous species Hypostomus auroguttatus Kner, 1854 had higher trypsin-like, chymotrypsin-like peptidase and β-glucosidase activity in the intestine when compared with the omnivorous species Pimelodus maculatus Lacepède, 1803, whereas the latter had more hepatic trypsin-like activity than the former. The peak of activity of the three enzymes in H. auroguttatus was recorded in the winter and spring. On the other hand, P. maculatus tended to have the more prominent peptidase and β-glucosidase activity in the summer, and the smallest in the winter. The intestine of H. auroguttatus had higher enzymatic (trypsin, chymotrypsin and β-glucosidase) activity than the stomach and the liver. For P. maculatus, the highest β-glucosidase activity was found in the liver. The enzymatic activity of H. aurogutattus did not differ between lotic and lentic systems, whereas P. maculatus had comparatively higher stomach and hepatic trypsin levels and hepatic chymotrypsin-like activities in the reservoir than down in the river. These findings indicate that, in H. auroguttatus, most digestive activity occurs in the intestine, which is long and adapted for the digestion of bottom-river vegetable matter and detritus. The seasons and the type of the system (lentic vs. lotic) seem to affect the enzymatic activity for these two species differently, a likely consequence of their different lifestyles.
Highlights
Most vertebrates, including fishes, possess digestive enzymes that allow them to digest the food that they consume, but variation exists among species in the activity of individual enzymes (CHAKRABARTI et al 1995, KUZ’MINA et al 1996, ALARCÓN et al 2001)
Concerning the -glucosidase activity, the activities in stomach and intestine were lower for P. maculatus than for H. auroguttatus (Table I)
Activities of peptidases with specificity for trypsin and chymotrypsin were consistently higher in stomachs and intestines of the iliophagous/herbivorous species H. auroguttatus when compared with the omnivorous P. maculatus
Summary
Most vertebrates, including fishes, possess digestive enzymes that allow them to digest the food that they consume, but variation exists among species in the activity of individual enzymes (CHAKRABARTI et al 1995, KUZ’MINA et al 1996, ALARCÓN et al 2001). A comparative study of the activity of these digestive peptidase and glycosidase enzymes can elucidate how different species use proteins and carbohydrates, and how they deal with variations in the availability of those nutrients among seasons and different habitats (HIDALGO et al 1999). The food preferences of fishes were established during the course of their adaptive radiation and the colonization of new habitats. This process required a broad array of different digestive mechanisms to successfully exploit the variety of foods available in an everchanging environment (DABROWSKI & PORTELA 2006, LÓPEZ-VÁSQUEZ et al 2009). For instance that of CHAKRABARTI et al (1995), have failed to find such correlation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
