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Published on: October 11, 2022
The response of digestive proteases to abrupt salinity decrease in the euryhaline sparid Sparus aurata L.
Eleni Psochiou1, Zissis Mamuris, Panagiota Panagiotaki
1Department of Biochemistry & Biotechnology, University of Thessaly, 26 Ploutonos Street, 41221 Larissa, Greece.
Summary
Juvenile gilthead sea bream showed no significant changes in stomach acid proteases or intestinal alkaline proteases after a salinity decrease. However, specific enzymes like elastase and carboxypeptidase were altered, particularly in the upper intestine.
Area of Science:
- Aquaculture and Fish Physiology
- Marine Biology
- Comparative Biochemistry
Background:
- Digestive enzyme activity is crucial for fish growth and nutrient assimilation.
- Understanding fish protease responses to environmental changes like salinity is vital for aquaculture sustainability.
- Gilthead sea bream (Sparus aurata) are euryhaline fish, but their digestive physiology under fluctuating salinity requires detailed investigation.
Purpose of the Study:
- To investigate the impact of abrupt salinity decrease on digestive protease activity in juvenile gilthead sea bream.
- To determine how different intestinal segments respond to salinity changes in terms of protease function.
- To correlate observed protease alterations with osmoregulatory roles and dietary protein digestion.
Main Methods:
- Transferring juvenile gilthead sea bream from 33 to 21 practical salinity units (psu) and maintaining for 15 days.
- Measuring activities of total acid proteases (stomach), total alkaline proteases, trypsin, chymotrypsin, elastase, and carboxypeptidases (A and B) in different intestinal segments.
- Analyzing protease activity distribution patterns across the stomach, pyloric caeca, anterior intestine, and posterior intestine.
Main Results:
- Salinity decrease did not significantly affect total acid proteases in the stomach or total alkaline proteases, trypsin, and chymotrypsin in the intestine.
- A distinct distribution pattern of major proteases (highest in posterior intestine, followed by pyloric caeca) remained unchanged by salinity reduction.
- Significant alterations in elastase and carboxypeptidase activities were observed, primarily in the pyloric caeca and anterior intestine, with specific changes noted for carboxypeptidase A and B.
Conclusions:
- While major digestive proteases show resilience to moderate salinity decrease, specific enzymes like elastase and carboxypeptidases are sensitive indicators of environmental stress.
- The differential response of proteases in various intestinal segments suggests specialized roles in osmoregulation and digestion under changing salinity.
- These findings provide insights into the physiological adaptability of gilthead sea bream and have implications for optimizing aquaculture practices during environmental fluctuations.
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