Changes in calcium content, histopathology and calreticulin expression in the juvenile Chinese mitten crab Eriocheir sinensis under different salinity conditions

The growth, development and reproduction of Eriocheir sinensis are influenced by salinity changes. In order to study the response of juvenile Chinese mitten crab to salinity, the crabs were exposed to 5 salinity conditions (0, 3, 6, 12 and 18‰) for 48 h. The calcium content was detected in the hepatopancreas, posterior gill, intestine, haemolymph, antennal gland and carapace. The hepatopancreas, posterior gills and intestines were selected for subsequent experiments, and their histopathological changes and calreticulin (CRT) gene expression levels were evaluated. The calcium content of hepatopancreas and intestine was highest at 6‰ salinity and that of gill at 3‰ salinity. With the increase in salinity, the degree of damage was more obvious in tissues. Compared with the control group (0‰), CRT expression in the gills decreased significantly. However, in the hepatopancreas and intestine, CRT expression increased at 3‰ salinity and decreased at 3–6‰ salinity. Overall, our results showed that juvenile E. sinensis could survive short-term exposure to saline water within a certain salinity range (<18‰). However, a high concentration of saline water exposed the juvenile crab to excessive stress, resulting in serious tissue damage, which was not conducive to the long-term survival of juvenile crabs.