Penis glands of the dugesiid planarian Girardia schubarti (Platyhelminthes, Tricladida, Paludicola)

In the penis glands of the dugesiid planarian Girardia schubarti, 6 secreto ry cell types were distinguished based on their histology and distribution. One cell type (type I) opens into the most distal part of the bulbar cavit y, 3 cell types (types IIa, IIb, and IIc) open into the ejaculatory duct, a nd 2 cell types (types IIIa and IIIb) open directly into the male atrium th rough the epithelium of the penis papilla. Secretory cells of types IIb, II c, and IIIa were identified as mucocytes. Types I, IIa, and IIIb produce a proteinaceous secretion. Fixation with neutral formaldehyde best preserves the integrity of the secretory granules of the penis glands. The distributi on, number, and histochemical affinities of the cell types of the penial gl ands may constitute differential taxonomic characters. The role of the peni s glands in maintaining sperm viability and in sperm transfer is compared w ith their function in other dugesiid species.