The Spermatogenic Cycle of Dermophis mexicanus (Amphibia: Gymnophiona)

Abstract

The general notion that amphibian reproduction in the tropics is non-cyclic and aseasonal (cf. Duellman and Trueb, 1986) is countered by the spermatogenic cycles of caecilians. In fact, for virtually all caecilians investigated, spermatogenic cycles (and particularly sperm release, fertilization, and hatching or birth) are synchronous and seasonal. Spermatogenesis has been described for members of four of the five currently recognized families of caecilians. Seshachar, in a series of papers, carefully described spermatogenesis in the ichthyophiid Ichthyophis glutinosus (1936, 1937, 1943), the uraeotyphlid Uraeotyphlus narayani (1939, 1945), and the caeciliaids Siphonops annulatus and Schistometopum (then Dermophis) gregorii (1942), and Gegeneophis carnosus (1945). Exbrayat (1986) and Exbrayat and Sentis (1982) examined the cycle of the typhlonectine Typhlonectes compressicaudus, and de Sa and Berois (1986) described that of the typhlonectine Chthonerpeton indistinctum. Wake (1968) discussed spermatogenesis in the caeciliaid Gymnopis multiplicata, that of a number of other species in less detail. She considered active spermatogenesis to be the entire period of spermatocyte production, maturation, and sperm release, because multiple stages of development of sperm are present in the testis much of the time.