The ultrastructural localisation of membrane-associated phosphatases in the integument of the earthworm Eisenia foetida.

Acid phosphatase was demonstrated in relation to the apical microvilli, though not in the epicuticular projections derived from them, and reaction products were rare at the level of the apical membrane between microvilli. Positive reactions occurred at the septate desmosomal level of the epidermal intercellular junctions. All reactions were associated with the inner leaflet of the membrane. The alkaline phosphatase technique was negative at all epidermal membrane sites.