320
MARINE MOLLUSCS AS HOSTS BOR SYMBIOSES
with one or more females, which usually takes place in June or July,
the males disappear. Thus males only become 1 year old or less.
Females become ovjgerous in their first summer but do not attain
maximum size before their second summer. Some do not attain this
until their third summer. Fully grown ovigerous females measure
from 9.4 to 10.8 mm in width. These carry from 7 957-9 456 eggs. The
P
FIGS. 214 and 215. Stage I (hard stage) Pinnotheresostreurn. (214) Female, dorsal view;
(215) female, ventral view. (Redrawn after Stauber, 1945.)
exact period for which the eggs are carried is not known but it is
believed to be from 3 to 5 weeks. Females only produce one batch of
eggs during the first year but may produce two batches during the second
and third years.
Ecology. Again, interested readers are referred to the detailed
ecological observations by Stauber (1945) and Christensen and McDermott (1958). It is known that in Delaware Bay, and presumably
also in other temperate regions, invasion of oysters by P. ostreum is