Publication Abstract

Triploidy in the Manila clam (Tapes philippinarum)

S.D. Utting

Research on polyploidy in molluscs began in America in the early 1980s in response to a request from the aquaculture industry for an oyster (Crassostrea virginica) that could be marketed throughout the year. Triploid oysters were produced which were theoretically sterile and which retained their meat quality during the summer months instead of diverting food reserves into gonad production. Since those trials, many more attempts at producing polyploid molluscs have been made with varying degrees of success. Much of the research has been carried out with the Pacific oyster (Crassostrea gigas). Methods of inducing triploidy have included the treatment of eggs with thermal shock, hydrostatic pressure, and the chemical cytochalasin B (CB). All treatments prevent the extrusion of one of the polar bodies, with the result that the egg contains a diploid set of chromosomes. At the MAFF Fisheries Laboratory Conwy, work on inducing triploidy and tetraploidy in the Manila clam (Tapes philippinarum) began in 1986. Adult broodstock clams had been introduced from the Pacific coast of North America in 1980 through the quarantine facilities at Conwy. But despite promising results from field trials and anticipated good commercial potential, the Manila clam industry in the UK expanded more slowly than expected. (In 1992, less than 50 tonnes was produced.) This was in part due to a strong lobby from UK marine conservation groups over the perceived negative environmental effects of Manila clam farming. These groups express concern that this non-native clam will recruit in the wild and displace native fauna.

Reference:

S.D. Utting, 1995. Triploidy in the Manila clam (Tapes philippinarum). Environmental Impacts of Aquatic Biotechnology, Oecd., 114-119