The susceptibility of seed oysters of Ostrea edulis L. and Crassostrea gigas Thunberg to natural infestation by the copepod Mytilicola intestinalis Steuer
1982
Dare, P.J.
Ostrea edulis and Crassostrea gigas seed of 5-45 mm length were exposed to Mytilicola intestinalis during the main (autumn) infestation season in the Lynher and Teign Estuaries, south-west England. C. gigas proved to be far less susceptible than O. edulis to infestation. In Ostrea edulis the numbers of copepodites acquired during 2 months were positively correlated with host size; no such correlation was apparent with C. gigas. C. gigas smaller than 25 mm were so rarely infested that the risk of them transmitting the parasite is considered to be negligible. Some juvenile parasites overwintered in larger C. gigas but grew more slowly than in O. edulis hosts of similar size and their survival to breed seemed unlikely. O. edulis as small as 5-10 mm acquired parasites but juveniles and adults overwintered only in larger seed (> 35 mm) and with 87% mortality. Female Mytilicola grew to 6 mm by early winter, thus suggesting that breeding can occur in larger seed in spring. O. edulis should be regarded as a potential vector, although the risk may be considered slight with seed smaller than 15 mm.
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