Sex and a snail's sperm: on the transport, storage and fate of dimorphic sperm in Littorinidae

Littorinid parasperm develop from a distinctive lineage of germ cells which exhibit a process of nuclear destruction that has apototic characteristics . Fragments of DNA and other nuclear breakdown products are incorporated in to secretion granules in parasperm that ultimately find their way tb the fe male bursa copulatrix. Spermatozeugmata are stored in the seminal vesicles and, if unused during the breeding season, they are recycled by phagocytosi s. Attachment between eusperm and parasperm is facilitated by an electrosta tic interaction of proteins. Detachment, caused by alkaline prostate fluid, occurs by the time the ejaculate reaches the tip of the penis. Thus transp ort of eusperm by parasperm to the female is unlikely. parasperm are steril e cells that may function in defense against rival eusperm as suggested by the presence of lysosomes, or they may act as nuptial gifts as they are pac ked with glycoprotein nutrients. Differences in the reactivity of different parasperm to specific lectins may enable separation of dimorphic sperm by lectin affinity chromatography, thereby facilitating future studies on indi vidual parasperm. In female Littorinidae, sperm are stored incapacitated in storage organs, or rarely in the ovary itself. In L. littorea serotonin ca used spawning of unencapsulated eggs, which, in the presence of activated s perm, became polyspermic.