THE JOURNAL OF EXPERIMENTAL ZOOLOGY 282:507–525 (1998) © 1998 WILEY-LISS, INC. Survey of the Oviduct of Salamandrids With Special Reference to the Viviparous Species HARTMUT GREVEN* Institut für Zoomorphologie und Zellbiologie der Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany ABSTRACT Urodeles include oviparous and a few obligately viviparous species that belong to one family, the Salamandridae. Oviducts of both groups have basically the same design, but some modifications became necessary as viviparous species evolved. The entire oviduct of urodeles is lined by a monolayered epithelium, which is regionally differentiated into large glands and smaller secretory cells rich in glycoproteins. Secretory products important for fertilization form the egg jelly, which also is present in viviparous species. In the latter species, however, there appear to be fewer oviductal convolutions and subdivisions of the glandular part of the organ, as well as fewer gland cells. Viscous, acidic secretory products predominate in viviparous species, whereas resis- tant neutral mucins predominate in oviparous species. In viviparous species, the caudal portion of the oviduct became altered to retain the developing offspring. This “uterus” lacks glands, but epithelial cells produce carbohydrate-rich material. Offspring remain in the uterus anywhere from several months to five years, depending on the species and climatic conditions. The Na + -K + -AT- Pase system, common in vertebrate epithelia, is used to regulate the intrauterine milieu. Subepi- thelial vessels mediate gas exchange and the removal of waste products, mainly urea. Secretions of the uterine epithelium may contribute to the fluid surrounding the young, but do not seem to support nutrition. Sources of nutrition for the young vary from one (sub)species to the next. Some feed on yolk reserves (Salamandra salamandra and certain of its subspecies), others on unfertil- ized eggs and siblings (other S. salamandra subspecies and Mertensiella luschani with subspe- cies), and yet others on degrading embryotrophic eggs as well as on cells derived from a specialized uterine trophic zone (S. atra and subspecies). Certain basic alterations in the uterine epithelium during pregnancy are most likely under endocrine control. Others, such as the flattening of cells, the discharge of secretory products, and the development of the trophic zone, may be induced by interactions with the offspring. J. Exp. Zool. 282:507525, 1998. © 1998 Wiley-Liss, Inc. Viviparity, a mode of reproduction in which young are carried in a parent’s body during a major por- tion or during the entire period of development, has evolved many times within the vertebrate phylum (for discussions of definitions: Wourms et al., ’88; Wake and Roth, ’89; Wake, ’93). Viviparous species are found in all three extant orders of Amphibia, most of them among the Gymnophiona, and only a few among Anura and Urodela (Wake, ’93). Of the urodeles, only members of the family Salaman- dridae, i.e. all species of the Palaearctic genus Salamandra and the related species Mertensiella luschani are obligately viviparous. The exact number of species and/or subspecies belonging to these genera is still a matter of debate (references in Greven and Thiesmeier, ’94). Larvae at diverse stages of development, or even metamorphosed young, are born in Salamandra species, but Mertensiella luschani gives birth only to trans- formed offspring. Embryos and larva develop in a modified caudal portion of the Müllerian ducts (= oviducts). Usually it is called a uterus, a term that is justified because the oviducts of most verte- brates are homologous and have similar functions. Nutritive support of the young during development ranges from the initial yolk stores to oophagy, adelphophagy, and even epitheliophagy (for refer- ences see Greven and Thiesmeier, ’94). The general bauplan and basic functions of the oviducts in viviparous salamandrids are largely similar to those of oviparous species. Neverthe- less, viviparity and the trophic patterns mentioned above, i.e. lecithotrophy (nutrients provided only *Correspondence to: Hartmut Greven, Institut für Zoomorphologie und Zellbiologie der Heinrich-Heine-Universität Düsseldorf, Univer- sitätsstrasse 1, D-40225 Düsseldorf, Germany.