Abstract
The developmental metamorphosis of larvae of a freshwater mussel, Anodonta woodiana (Lea, 1834), under parasitizing on the goby Rhinogobius flumineus, was observed. The larvae embedded in the paraffin was sectioned and stained by the borax carmine and the Azan. The digestive tract was formed at about 42 hours after parasitized. The posterior adductor muscle was formed after the larval adductor muscle shifted anteriorly from the center in vertical section. The villus-like tissue stained blue was formed inside of the mantle cells in contact with host tissues and it disappeared before the mussel larva detached off host fish. It suggests that the villus-like tissue functions to digest and absorb body fluid of the host fish.
