RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) MARKERS REVEAL CROSS-FERTILIZATION IN BIOMPHALARIA-GLABRATA (PULMONATA, BASOMMATOPHORA)

The freshwater, schistosome-transmitting snail, Biomphalaria glabrata is a simultaneous hermaphrodite which can reproduce by both cross-and self-fertilisation, but despite the medical importance of this species , little is known about the mating strategies adopted by wild-type ind ividuals from natural populations. The identification of cross-fertili sed progeny is a prerequisite for both evolutionary studies of the rel ative fitness of different reproductive strategies, and for the produc tion of exclusively out crossed Fl populations for genetic mapping of biologically important phenotypes, most notably, resistance to schisto some infection. In this study, parents, offspring and 'synthetic offsp ring' (controls) from four families of B. glabrata recently derived fr om wild populations were analysed using the Random Amplified Polymorph ic DNA (RAPD) assay. RAPDs were used because they reveal more genetic variation, require less tissue (juvenile snails were only 4-5 mm diame ter) than protein electrophoresis, are less laborious than other molec ular analyses, and do not require sequence data. Seven of the 19 arbit rary sequence, oligonucleotide primers used gave bands that were polym orophic between pairs of parent snails. Scoring the offspring for the presence/absence of these polymorphic bands showed that all the offspr ing tested were the products of cross-fertilisation. This study provid es the first demonstration of the applicability of the RAPD technique to an analysis of fertilisation in wild-type B. glabrata.