The response of digestive enzyme activity in the mature Chinese mitten crab, Eriocheir sinensis (Decapoda: Brachyura), to gradual increase of salinity
Mature Chinese mitten crabs, Eriocheir sinensis, were exposed to brackish water or seawater as an obligatory part of their reproductive migration. Physiological and biochemical reorganization were needed to adapt them to this migration. To understand the digestive adjustments of Eriocheir sinensis at biochemical level during this transformation from freshwater to seawater, the response of the activity of five digestive enzymes (amylase, cellulase, pepsin, trypsin and lipase) in the
... in the hepatopancreas to salinities increasing gradually from 0 (freshwater) to 35 (seawater) was analysed in mature females and males. Digestive enzymes exhibited significantly higher activities in the hepatopancreas of males than those of females, except lipase. In females, amylase, pepsin and trypsin activities began to decrease significantly as the salinity reached 28, and cellulase activity decreased at 35; in males, a considerable decrease in the activity of digestive enzymes, except lipase, was observed at 21 and higher salinities, while an increase was observed at 14. Reduced enzyme activities at elevated salinities suggest that the digestive capacity of crabs for diets becomes weak, and all these digestive enzymes participated in digestive adjustments during osmoregulation. The initial salinity which induced the decrease of enzyme activity was lower in males than in females, indicating that females were more tolerant to elevated salinities than males from the point of digestive biochemical modulation.