Self-fertilization in the freshwater snails Helisoma duryi and Helisoma trivolvis

Abstract

Fifty specimens of five strains (10 per strain) of Helisoma duryi from Lima (Peru), St. Croix (Virgin Islands), Formosa (Brazil), Cartago (Costa Rica) and St. Vincent (Lesser Antilles), reared in isolation for about 150 days, laid 103 eggs. The numbers of eggs laid by the 10 specimens of each strain were respectively (viable eggs in parenthesis): 44 (26), 1 (1), 5 (0), 15 (7) and 38 (0). Egg production widely varied between the individuals of each strain, there being in all strains, except St. Vincent, a number of specimens (3 to 9) which did not lay any eggs. After the observation period the isolated specimens, including those that laid no eggs, readily engaged in cross-breeding when mated and brought forth large numbers of eggs. Self-fertilized F1S are fully interfertile, producing normal cross-fertilized offspring. Ten specimens of Helisoma trivolvis (strain from Zempoala, Mexico), also reared in isolation for about 120 days, laid 646 eggs, of which 74 were inviable. Our data, added to those from a few previous studies cited in the text, show that self-fertilization is not so efficient an alternative mode of reproduction in H. duryi as in many other planorbids (it is a little more efficient in H. trivolvis than in H. duryi). Thus, H. duryi benefits much less from functional hermaphroditism which, besides other advantages, enables a single virgin individual to found a new population.

Selfing and outcrossing in hermaphrodite freshwater gastropods (Basommatophora): where, when and why

“…Larambergue (1939) andParaense &Correa ( 1988) give a list of about 30 selffertile Planorbidae species, to which Biomphalaria pfez$eri (Krauss) (Vianey-Liaud, 1984) and Bulinus cernicus (Morelet) (Rollinson, Kane & Lines, 1989) must be added. Absolute self-sterility has been advocated in Planorbis caritanus (Muller) (Larambergue, 1939) and in Helisoma duryi (Weatherby) (Madsen, Thiongo & Ouma, 1983).…”

A bacterial artificial chromosome library for Biomphalaria glabrata, intermediate snail host of Schistosoma mansoni

“…Molluscs are a highly diverse group that includes some of the largest, longest living, and most intelligent invertebrates. Genome information will instruct on several remarkable properties of molluscs such as shell formation (biomineralization; Milet et al 2004), the evolution of body asymmetry (Schilthuizen & Davison 2005), and hermaphrodism (Paraense & Corrêa 1988). Molluscs are also being used to study pharmo-toxicology (Terlau & Olivera 2004); neuroendocrinology (Altelaar et al 2005); parthenogenesis (Jokela et al 2003); and the molecular basis of behavior and learning (Williamson & Chrachri 2004, Zhurov et al 2005.…”

Molluscicidal activity of Physalis angulata L. extracts and fractions on Biomphalaria tenagophila (d'Orbigny, 1835) under laboratory conditions

“…The culture was mantained in the Department of Biology according to Paraense and Corrêa (1988), and the snails fed with fresh lettuce (Lactuca sativa L.).…”