The organisation, fine structure and function of the excretory systems of the estuarine bivalve Scrobicularia plana (da Costa) and the freshwater bivalve Anodonta cygnea (Linne) and other selected species

Abstract

The organization, fine structure and function of the excretory systems of Scrobicularia plana and Anodonta cygnea were studied.

Ultrastructural evidence of a site capable of producing an ultrafiltrate of the blood, the initial stage of urine production, was found in the pericardial glands. The glands, formed by extensive infolding of the auricular epicardium are lined by podocytes which form the filtration site. In the main species under investigation the pericardial glands elaborated from the auricle expand into the pallial sinuses of the mantle. Conclusive evidence was found of openings from the lumen of the gland into the pericardium.

The pericardial glands of eight other species were also examined. Those of Corbicula manilensis, Polymesoda caroliniana, P. maritima, Dreissena polymorpha and Mya arenaria appeared similar. A similar arrangement was found in three species: Nucula nucleus, Mytilus edulis and Pecten maximus, in which the gland is confined to the auricle (believed to be the primitive condition). In all species a highly ordered slit diaphragm bridges the filtration slits of the podocytes.

A comparative study of the anatomy and ultrastructure of the kidney of Scrobicularia and Anodonta was undertaken and the observations considered in relation to function and basic organization of the bivalve kidney.

Ferritin tracer experiments revealed selective uptake of ferritin from the blood in the pericardial glands and proximal limb of the kidney of Scrobicularia.

A brief study of tidal influence on pericardial gland and renal activity of Scrobicularia indicated that there is no synchronous activity or rhythm.