Aspects of Osmotic and Ionic Regulation inCorophium Volutator(Pallas)

Experiments have been made to elucidate the problem of hyperosmotic regulation in the mud-dwelling euryhaline amphipod, Corophium volutator. The animal produced urine hypo-osmotic to the blood when acclimatized to low salinities, and isosmotic urine at salinities above 20%. The restricted permeable areas of the cuticle have been localized by silver staining. Over a range of salinities from 1 to 35 % C. volutator was found to maintain Na + , K-−, Ca 2 + , Cl-−, more concentrated than the medium, and Mg 2 ~ less concentrated. The importance of these mechanisms in assisting hyperosmotic regulation is discussed.