Abstract:To evaluate the breeding effect of sea cucumber (Apostichopus japonicus) salt tolerant strains, the growth, feeding and digestive physiological changes of the fourth generation (G4) and the fifth generation (G5) sea cucumber strains under low and high salinity environments were studied. The results showed that the growth of G4 and G5 were similar in low salt environment during a 30-day experiment. The final body weight in low salt environment decreased with the decrease in experimental salinity, and the final body weight in high salinity environment decreased with the increase in experimental salinity. The specific growth rate (SGR) and feeding rate (FR) of salinity 22 and salinity 35 were not significantly different from those of the control group at salinity 31 (P>0.05). In the salinity range of 18~31, the protease activity of G4 and G5 decreased with the decrease in salinity, and the lowest value was 1.55 U/mgprot observed in the G5. In the salinity range of 31~39, the protease activity of each experimental group decreased with the increase in salinity, but there was no significant difference between salinity 35, 37, and control group (P>0.05). There was no significant difference in amylase activity between G4 and G5 with the change in salinity; in the range of salinity 18~31, the protease activity of the G4 and G5 was not significantly different. The lipase activity of sea cucumber decreased with the decrease in salinity, and the lipase activity of salinity 18 and salinity 22 was significantly lower than that of salinity 31 (P<0.05). The results showed that there were significant differences between selected sea cucumbers and common sea cucumbers in adapting to growth, feeding, and activating digestive enzyme activities under different salinity treatments. The stability of breeding traits was strong in G4 and G5, and the directional breeding played an active role in genetic improvement of stress resistance in sea cucumbers.
