Abstract:Indoor experiments were conducted to investigate the effect of constant light intensity on physiology and ecology characteristics of swimming crab(Portunus trituberculatus).The oxygen consumption rate(OCR),ammonia excretion rate(AER),O:N ratio,lactic acid(LD),energetic contents in hemolymph and respiratory enzyme activities including hexokinase(HK),pyruvate kinase(PK),succinate dehydrogenase(SDH)and lactate dehydrogenase(LDH)were tested in five constant light intensity treatments(0,200,800,1 500,3 500 lx).The main results were as follows:1.Light intensity influenced the OCR and AER significantly(P<0.05).The oxygen consumption rate of the crab under 200-1 500 lx was significantly higher than those of the crab under 0 lx and 3 500 lx(P<0.05).The ammonia excretion rate of the crab under 1 500 lx was significantly lower than others(P<0.05).2.Light intensity influenced total protein,but did not influence other energetic contents and O:N ratio significantly(P>0.05).Our results suggest that protein is used preferentially as energy source.3.Marked differences were found in LD(P<0.05).The LD in muscle of the crab under 1 500 lx was lowest.4.Different light intensity influenced different respiratory enzymes differently.Under 1 500 lx,the activity of HK and PK were at a high level.Glycolysis went faster and produced more energy.The activity of SDH was at a high level,while LDH was low.Aerobic metabolism was at a higher level,providing more energy for a continuous motion of crab The results revealed that light intensity affected respiratory metabolism,and the crab at 1 500 lx had higher metabolism while under less stress.So about 1 500 lx may be the better illumination condition of the crab culture industry.