Studies on The Reproductive Biology of Gastropods: Part 1. The Systematic Distribution of Egg Retention in the Subclass Pulmonata (Gastropoda)

Summary

Thus far, no pulmonate snail has been unequivocally demonstrated to be viviparous. Most pulmonate snail are oviparous, i.e. they release each egg immediately after its formation On the basis of several years of observations and literatute search, a list of known ovoviviparous pulmonates (here defined sensu lato, as those animals which retain their eggs instead of releasing them right away) is presented. Ovoviviparity is apparently rare compared with oviparity; it is absent from the entire freshwater order Basommatophora and from all families of slugs. Ovoviviparous reproduction is most common in such families as the Achatimdae, Subulinidae, as well as in several groups of the suborder Orthurethra. On the basis of this survey. it appears that while approximately one-half of the more than sixty families of stylommatophoran families contain at least one ovoviviparous species, the total number of species involved is small.