Ultrastructure of the excretory organs and urinary component of the marine bivalve, Atrina (S.) Pectinata

1. 1. Auricle epithelial cells of Atrina (S.) pectinata had an ultrafiltration site similar to that of podocyte and kidney epithelium was composed of absorptive cells with brush border, basal infoldings, invaginations of aplcal cytoplasmic membrane and dense granules like secondary lysosomes. 2. 2. Osmolality, Na⁺ and Cl^- contents of the blood, pericardial fluid, urine and sea-water were almost identical. 3. 3. Most free amino acids and some K⁺ were reabsorbed from the urine. 4. 4. Taurine and ammonia were concentrated into the urine. 5. 5. Blood protein was partially passed into the pericardial fluid and mostly reabsorbed from the urine.