The structure of the ctenidium in the Pacific oyster Crassostrea gigas was examined. The inhalent orifice was located in the ventral side the pallial fold to the apex. Two exhalent orifices were in the dorsal side. One was located from the pallial fold to the adductor near the left and right ctenidia, and the other from the adductor to the apex near the left ctenidium. The left and right ctenidia were not divided from the pallial fold to near the labial palp. The gill type showed the heterorhabdic pseudolamellibranch: the primary filament and the ordinary filament were joined by the inner-filament connecting membrane and the inner-laminar connecting membrane.
Pacific oyster
ctenidium
exhalent orifice
food groove
heterorhabdic pseudolamellibranch
inner-filament connecting membrane