Ingestion size of food microalgae of the Pacific oyster Crassostrea gigas larvae

ABSTRACT Digestibility index of 12 phytoplankton species were invested during the larval development sizes. Ingestible size of phytoplankton varied depending on larval sizes: Isochrysis galbana , I. aff . galbana , Pavlova lutheri , Chlorella ellipsoidea , Nannochloris oculata was ingested 94.2-99.7% all larval sizes. Cheatoceros calcitrans , C. gracilis and C. simplex could ingest over 90.0% after umbo stage (mean shell length 189.3 ± 13.8 μm). Phaeodactylum triconutum , Dunaliella tertiolecta and Tetraselmis tetrathele could not ingested D-shaped larvae (shell length 65.0-100.0 μm) but ingested 97.3-99.7%, 43.3-99.3%, 48.5-99.3% after then larval stages, respectively. But Thalassiosira weissflogii was ingested 1.0-1.7% only at full grown stage. Over 50.0% ingestion cell size was D-shape stage larvae with smaller than mean 102.3 μm in shell length could ingest phytoplankton with 4.6 μm in both major and minor axis and up to 9.3 μm in minor axis basis for larger than mean 158.3 μm in shell length, respectively. At all larval stages, phytoplankton with larger than 10.0 μm in both major and minor axis could not be ingested.