Feeding Physiology And Larval Rearing Of The Pearl Oyster Pinctada Fucata

In the paper, an optical microscope was used to observed the ingestion and digestion process of Pinctada fucata larvae, ten species of microalgae were tested for ingestion and digestion in the larvae to choose an oppropriate diet. The mixture microalgae species with simalar size but different surface structures and similar surface structure but different sizes were fed to the P.fucata respectively, selective feeding was detected by cells count in the remaining mixture microalgae; four species of microalgae at different concentrations were fed to the P.fucata respectively, the digestion degree of microalgae with different species and concentrations were detected in feces. Single and mixed species of microalgae, un-ingestable and ingestable species of microalgae,different concentrations microalgae and different concentrations shell power were fed or added to the larval rearing to detected growth and survival of larvae. So as to provide theoretical guidance on feeding of larval rearing of P.fucata, the results are as follows:1. Ingestioin and digestion of 10 species of microalgae by Pinctada fucata larvaeTen species of microalgae（Platymonas subcordiformis, Dunaliella salina,Chlorella vulgaris, Nannochloropsis oculata, Dicrateria zhanjiangensis, Pavlova viridis,Isochrysis galbana, Chaetoceros muelleri, Phaeodactylum tricornutum and Nitzschia clostericm） were tested for ingestion and digestion in P. fucata larvae using an optical microscope to choose an oppropriate diet. An experiment was condueted using 2 d（D-shaped stage）, 8 d（early umbo stage）, 14 d（umbo stage）, 18 d（late umbo stage） and22 d（eye-spot stage） old larvae, respectively. Larvae were stocked in flasks and fed 105ind·mL^-1 of each species individualy, larvae were observed under the microscope at 1 h post feeding to detect if they were ingested or not and then were transferred to filtered clear seawater, and digestion status of the ingested algae were observed at 1 h, 2 h and 4h after sieved. The result showed that C. vulgaris, N. oculata, D. zhanjiangensis, P.viridis and I. galbana were ingested by the five stages larvae; D. salina and C. muelleri were just ingested only by 18 d older larvae. Among others, only D. zhanjiangensis, P.viridis and I. galbana were digested fully, while C. vulgaris and N. oculata were hardlydigested. P. Subcordiformis, with the increasing concentration, the microalgae will partial digested or not digested, P. tricornutum and N. Clostericm were not ingested at all though it was fed as main food in usual larval culture practice of this animal.Therefore, only P. viridis, D. zhanjiangensis and I. galbana should be used for larvae rearing of P. fucata until other species are identified as suitable ingested and digested for larvae feeding at an appropriate concentration, and less but frequent.2. Effect of ingestion and digestion on different types and concentrations microalgae by pearl oyster Pinctada fucataAn experiment was conducted to explore the effect of ingestion and digestion on different types and concentratios microalgae from the different sizes, surface structures,biochemical composition and concentrations by P. fucata. The mixture of C. muelleri and D. zhanjiangensis with similar size and the mixture of P. subcordiformis and C.vulgaris with different sizes were fed to the pearl oyster respectively, cells count was detected in the remaining mixture microalgae. C.muelleri, D.zhanjiangensis,P.subcordiformis and C. vulgaris at four kinds of concentrations respectively were fed to the pearl oyster to compare the digestion degree of microalgae in feces. The results show that the selective feeding not significant（P > 0.05） between the microalge with similal size, while the ingestion rate raised on microalgae with the increasing sizes（P <0.05）. Four species of microalgae hardly digestion sequence is P. Subcordiformis > C.Vulgaris > C. Muelleri > D. Zhanjiangensis, the digestion degree decreased with the increase of diet concentration.3. Application of microalgae and shell power for larval rearing of Pinctada fucataTo optimize feeding strategy for pearl oyster P. fucata larval culture, effects of microalgae species, algal mix, diet concentrations and shell power concentrations on growth and survival rates of the larvae were investigated in this study. growth and survival rate were determined by feeding easy-digested D. zhanjiangensis, P. viridis, D.zhanjiangensis+P. viridis, P. tricornutum（not ingested as indicated above）, and different concentrations of D. zhanjiangensis, 50 mg·L^-1, 100 mg·L^-1, 150 mg·L^-1 and 200 mg·L^-1shell power were added to the pond at larval rearing. As a result, better growth and survival rates were observed in the larvae fed with mixed algae than single algal species（P < 0.05）. The un-ingestible algae could not be used by the larvae and high concentration of algae was detrimental to larval growth and survival. When the shell power concentration added more than 200 mg·L^-1 the larvae shell length and survivalrate is significantly（P<0.05） higer than that not added. These findings suggested that D.vhanjiangensis and P. viridis can be used as staple foods in the larval culture practice of P. fucata, feeding in blended at an appropriate concentration, and less but frequent.Shell power can be used for larval culture and concentration had better higher than 200mg·L^-1.