Studies On Metabolic Physiology And Energy Budget Of Crassostrea Hongkongensis

The Crassostrea hongkongensis was one of the important marine biological resourcespecies in our country. It mainly distributed in seaboards of Guangdong and Guangxi.Respiration and excretion of the shellfish are basic physiological activities, also are theimportant contents of shellfish energetics, aquaculture capacity research and evaluationbivalves marine ecosystem impact.The effects of body size on physiological change of metabolism of the C. hongkongensisis studied under controlled laboratory condition in autumn, the energy budget is established.The aim is to investigate the carrying capacity for aquaculture of C. hongkongensis, andprovide the theoretical guidance on the physiology to analyze the impacts of the C.hongkongensis culture on environment. The main results are summarized as follows：The oxygen consumption rate and excretion rate of C. hongkongensis were significantdifferent （P <0.01）, O/N and N/P ratio had no significant effect between different dry tissueweight （P>0.05）. The oxygen consumption rate （Ro）, ammonia excretion rate （Rn）, andphosphorus excretion rate （Rp） of C. hongkongensis were correlated negatively with the drytissue weight （DW）. The correlations can be expressed by the equationsRo=1.8232W^-0.7600（r²=0.8313, P<0.01）, Rn=0.0930W-0.6582（r2=0.7444, P<0.01）,Rp=12.5555W^-0.8874（r²=0.9224, P<0.01）. The values of O/N were higher, N/P ratios showedascendant trend with the dry tissue weight increasing.Energy budget is the key content of bivalves energetics. Bivalves obtain energy byfiltering organic food. The some parts discharged as dejection, some consumed for their ownrespiration, a little excreted through excretion, and the remaining parts energy become theorganism composition for growth, then many scholars have established energy budget modelsof the different bivalves. The energy budget equations were listed as follow:A:100C=27.21F+16.46R+1.23U+55.10PB:100C=33.22F+7.22R+0.63U+58.93PC:100C=58.22F+6.62R+0.67U+34.49PD:100C=64.22F+7.33R+0.70U+27.75P The results showed that ingestion rate, assimilation efficiency and growth rates of C.hongkongensis gradually decreased with the dry tissue weight increased. The equations of theenergy budget showed that the energy of growth ranged from27.75%to58.93%, respirationfrom6.62%to16.46%, defecation from33.22%to64.22%and was under2%. Defecationenergy was positively correlated with the dry tissue weight, but excretion energy had nosignificant correlation. The energy for growth decreased with the dry tissue weight increased,most of the accumulated energy was for growth and sexual maturity.