Ultrastructural observations on the body wall of the leech, Batracobdella picta

A series of closely spaced annulations surround the surface of the body of Batracobdella picta. The epidermis is covered by a thin cuticle which is composed of several layer of orthogonally arranged, fibrous bundles. Numerous fine projections carpet the surface of the cuticle and appear to be derived from microvillar processes which extend through the cuticle from subjacent epithelial cells. Septate junctions occur between adjacent epithelial cells, and hemidesmosomes with associated tonofilaments appear to anchor the epithelium to the overlying cuticle and to the basal connective tissue. The epithelial cells contain abundant organelles including granular endoplasmic reticulum, mitochondria and Golgi complexes. The cytology of the body wall of B. picta is compared with that of other annelids.