Penis Glands of the Dugesiid Planarian Girardia schubarti (Platyhelminthes, Tricladida, Paludicola)

In the penis glands of the dugesiid planarian Girardia schubarti, 6 secretory cell types were distinguished based on their histology and distribution. One cell type (type I) opens into the most distal part of the bulbar cavity, 3 cell types (types IIa, lib, and lIc) open into the ejaculatory duct, and 2 cell types (types lila and IIIb) open directly into the male atrium through the epithelium of the penis papilla. Secretory cells of types Ib, lic, and lila 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 distribution, number, and histochemical affinities of the cell types of the penial glands may constitute differential taxonomic characters. The role of the penis glands in maintaining sperm viability and in sperm transfer is compared with their function in other dugesiid species. Additional key-words: flatworm, turbellarian Considering the central position of the reproductive system in resolving problems of turbellarian systematics and evolution, information about the ultrastructure of the reproductive organs and associated glands in triclads is surprisingly scant (Rieger 1981). Detailed histological studies are also needed because histological characteristics are usually used for taxonomic identification, and also because they are more accurate after a suitable fixation than is the shape of the copulatory organs in such soft-bodied animals. According to Sluys (1996), anatomical variability often makes species recognition in Girardia complex and difficult. Few recent studies deal with the histology and ultrastructure of the reproductive organs of triclads. Marinelli & Vagnetti (1977) analyzed the ultrastructure of the sperm ducts, penis bulb, and penis papilla of Schmidtea lugubris (SCHMIDT 1861). Fischlschweiger & Clausnitzer (1984) and Fischlschweiger (1990, 1992, 1994) analyzed ultrastructural aspects of the reproductive system of Girardia tigrina (GIRARD 1850) and Cura foremanii (GIRARD 1852). Moretto (1996) studied the histology and ultrastructure of the reproductive system of Girardia sanchezi (HYMAN 1959) and G. bonaerensis (MORETTO 1996) and proposed using the secretions of the penis glands in relation to the physiology of the copula as differential taxonomic features for these species. a Author for correspondence. E-mail: ipp@cirus.unisinos. tche.br Taxonomic studies have contributed to the knowledge of the microscopic anatomy of the reproductive system of Girardia schubarti (MARCUS 1946) (see Marcus 1946; Kawakatsu et al. 1976, 1982, 1983, 1984b, 1985, 1986), but have not provided histological data about the constitution of the penis glands. The reproductive biology of most dugesiid species, including G. schubarti, is unknown. The objective of the present paper is to provide a detailed description of the histology of the penis glands of G. schubarti and a first histochemical characterization of their secretions in order to support further studies on the physiology of the male copulatory organs.