Ultrastructure of the podocyte of the pericardia! gland in marine bivalve Pinctada radiata and in fresh water bivalve Anodonta rubens were investigated. Obvious differences in shape, distribution and number of cytoplasmic organelles of the podocytes observed in both species are suggested to be related to the difference of their habitats. In addition, the pedicels of the basal membrane are more complex in A. rubens than those in P. radiata, and also the surface of the apical cell differs in structure. The suitability of podocyte structure to its function is discussed.