The histochemistry of the clitellum of Tubifex tubifex (annelida: oligochaeta).

The histochemistry of the clitellar glands of Tubiflex tubiflex is reported, together with the ultrastructure of mature secretion units. The distribution and ultrastructure of mucous and granule cells are consistent with published accounts of tubificid citella, thus indicating an absence of intrageneric variation. Mucous cells contain homogenous electron lucent globules which are rich in neutral and acidic mucopolysaccharides and are non-reactive with techniques designed to reveal protein. Type I cells possess structured granules composed of tyrosine-containing basic protein and carboxylated acid mucopolysaccharides. The granules of type II cells are heterogenous and contain several 0.3--0.7 micrometer inclusions of acidic protein with identifiable tyrosine, tryptophan and cystine. The inclusions occur within a matrix composed of neutral mucopolysaccharides and carboxymucin. Type III cell granules possess 0.2--0.5 micrometer inclusions within an electron dense matrix and are rich in neutral and carboxylated acid mucopolysaccharides and basic protein containing tyrosine, tryptophane and cystine. Clitelar carboxymucins are characterized by their stability to beta-glucoronidase, hyaluronidase, neurominidase and acid hydrolysis. A pyridine-extractable lipid moiety within the clitellar secretions was not detected. The results are discussed in relation to cell function during cocoon deposition and, comparatively, with those documented for other oligochaete families.