Virgin homozygous black pigmented and albino Biomphalaria glabrata are paired during a period varying from 1 to 20 days. The rate of cross-fertilized parents is statistically similar for the various lengths of pairing. As a whole, nearly 80% of the albino snails produce a pigmented progeny. This production begins as soon as the snails are mated and continues after their separation. To measure the actual use of the allosperm, its use during the postmating period must be added to the length of mating. So, it appears that the real use of the allosperm is statistically constant (mean slightly inferior to 8 weeks) and not related to the length of the previous pairing.

Experimental study of the life history of Echinostoma parvocirrus n. sp. (Trematoda: Echinostomatidae), a larval parasite of Biomphalaria glabrata in Guadeloupe.SUMMARY. The larval stages and adult of a new species of Echinostome with 37 collar spines originating from Guadeloupe are described. The first intermediate host is the snail vector of Schistosoma mansoni in this island, Biomphalaria glabrata. Metacercariae encyst in the pericardial sac of the same snail and the physid snail Physa marmorata, as in kidneys of tadpoles of Bufo marinus. Adult develops experimentally in ducklings of Cairina moschata and in canaris but not in ducklings of Anas platyrhyncos, pigeons, chicks, albino mice, Ratlus rattus, or wild and albino R. norvegicus. The natural final host is unknown.

When one pigmented Biomphalaria glabrata is mated with 1 to 20 albino snails, the percentage of albino parent producing pigmented offspring decreases while the percentage of parent laying albino offspring increases. If the number of snaisl/group increases, the mean duration of the use of allosperm decreases.

A correspondence analysis of shell measurements taken from 521 widely dispersed specimens of the African aquatic pulmonate snail Biomphalaria pfetyereri suggests the existence of eight morphological groups. These groups appear to relate to either ecophysiological factors or to factors associated with the stability of the freshwater system rather than to aspects of geographic distribution and genetic isolation.