Effects of Water Temperature and Macroalga Species on Feeding,Respiration and Ammonia Excretion of Sea Urchin Hemicentrotus pulcherrimus

In this study,sea urchin(Hemicentrotus pulcherrimus)with initial body weight of(0.55±0.16)g were reared in a 0.3 m×0.4 m×0.5 m white plastic tank at stocking density of 100 individuals per tank and overfed five common species of macoralgae Undaria pinnatifida,Leathesia difformis,Ulva pertusa,Enteromorpha intestinalis,and Chaetomorpha moniligera to study the feeding selectivity of sea urchin for algae by calculation of dry macoralgae weight.Also,the sea urchin with initial body weight of(0.67±0.32)g were reared at water temperature of 10.1,15.6 and 20.3℃and fed the same macroalgae for 2 days,and then 10 individuals of similar size sea urchin were placed in a 1 L sealed conical flask to determine the oxygen consumption and ammonia excretion rates.The results showed that the descending order feeding selectivity of sea urchin to five species of algae was expressed as U.pinnatifida,L.difformis,U.pertusa,E.intestinalis,and C.moniligera,prefering to U.pinnatifida.The daily relative food intake of the sea urchin was significantly affected by temperature and macoralga species,the maximal value at water temperature of 15.6℃,and significantly higher in U.pinnatifida group than that in other groups(P<0.05),with the minimal in C.moniligera group.Oxygen consumption rate was shown to be increased gradually in the sea urchin with the increase in water temperature in different groups,the maximal in U.pertusa group at the same temperature.The ammonia excretion rate,however,was first increased and then decreased with the warming water temperature,the maximal at 15.6℃.The findings will provide a foundation for the ecological breeding of sea urchin and for the construction of a green integrated aquaculture model in sea cucumber ponds.