Effects of Temperature on the Feeding Rate and the Digestive Enzymes Activities of Eogammarus possjeticus

Abstract:

he amphipod crustacean Eogammarus possjeticus is an ideal live feed for fish and shrimp. However, little is known about the optimal aquaculture conditions for this species. Here we investigated the effects of temperature on the feeding rate and digestive enzymes activities of E. possjeticus using physiological ecology method and enzymatic analysis. Our results demonstrated that there were significant differences in digestive enzymes activities between groups treated at different temperatures (P<0.01). In the range of 15−25℃ the activities of pepsin, trypsin and amylase in E. possjeticus were elevated along with the increase of temperature, especially higher above 20℃. Thus, the optimal temperature for digestive enzymes activities should be 20−25℃. The amylase/trypsin (A/T) value was used to evaluate the feeding habits of crustacean. The A/T values were between 1.2 and 1.5 with small fluctuation, which indicated that the larvae of E. possjeticus had preference to plant diets. The feeding rate of E. possjeticus juveniles was largely affected by temperature (P<0.05), and the predicted maximal feeding rate was 89.84% according to the correlation equation (y= −0.754x2+33.297x−277.57, R2 =0.958) between 20℃ and 25℃. The predicted maximal feeding rate of adults was 32.47% according to the correlation equation (y=−0.247x2+10.463x–78.287 (R2=0.998) at around 20℃. The assimilation rates were similar between the juveniles and the adults of E. possjeticus. The maximal assimilation efficiency was 59.86% for juveniles, and 56.86% for adults, and the corresponding optimal temperatures were 21.30℃ and 21.24℃ respectively. These data suggested that 20−25℃ could be an appropriate temperature range for the cultivation of E. possjeticus.