David M. Sever1, Lisa C. Rania1, and Rossana Brizzi2
The Lissamphibia usually is considered monophyletic and consists of three orders, Caudata (salamanders and newts, 415 species), Anura (frogs and toads, 4100 species) and Apoda (caecilians, 165 species). In caudates, absence of sperm storage is the ancestral condition (three families), and sperm storage in cloacal sperm storage glands, spermathecae, is a synapomorphy for the Salamandroidea (seven families). The anatomy and phylogeny of caudate spermathecae have been studied extensively (reviewed by Sever and Brizzi, Journal of Experimental Zoology 282:460-476). We provide new ultrastructural observations on spermathecae of European Triturus, demonstrating similar patterns of sperm storage and degradation in sister taxa subjected to different ecological conditions over a wide geographic area. Internal fertilization has convergently evolved in a few anuran taxa, but females of just one species, Ascaphus truei (Leiopelmatidae) are known to possess oviducal sperm storage tubules. We review recent findings on sperm migration and storage in A. truei, and compare structural and functional similarities of these mechanisms to those of other vertebrates with female sperm storage. Finally, we report on evidence for sperm storage in female caecilians. Although all caecilians fertilize internally and many are viviparous, female sperm storage has not been heretofore reported.
1Department of Biology, Saint Mary's College, Notre Dame, Indiana 46556 USA dsever@saintmarys.edu
2Department of Animal Biology and Genetics, University of Florence, Italy brizzi@dbag.unifi.it