Morphological alterations in the digestive diverticula of Mizuhopecten yessoensis (Bivalvia: Pectinidae) from polluted areas of Peter the Great Bay, Sea of Japan

This paper describes the histology of the digestive diverticula of Mizuhopecten yessoensis (Jay) sampled from one reference and three polluted stations in Peter the Great Bay, Sea of Japan. A wide spectrum of morphological changes has been identified in scallops from polluted sites. Some changes were typical of only one of the polluted stations, such as the occurrence of new cell types, transitive cells with attributes of both digestive and basophilic cells, altered basophilic cells at Station B, the occurrence of atrophic tubules at Station C and mass shedding of basophilic cells in tubule lumina at Station D. Other changes were common in scallops from all polluted sites, such as vacuolization and shedding of digestive cells and necrosis of digestive tubules. Two different responses of the basophilic cells may represent an adaptive-compensatory reaction of the digestive diverticula to damage, i.e. loss of digestive cells and disruption of intracellular digestion. The regeneration of the digestive diverticula through the formation of new tubules was observed in scallops from all stations but at Station D there was incomplete regeneration as evidenced by the smaller numbers of digestive tubules per unit area of digestive diverticula. Histological changes in the scallop digestive diverticula seem to be related to pollution of Peter the Great Bay.