164
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
not unique since it has been reported for certain species of Haplosporidium (Granata, 1914 ; Debaisieux, 1920 ; Jirovic, 1936 ; CEtullery, 1953 ;
Ganapati and Narasimhamurti, 1960 ; Barrow, 1961).
Pathology. Although the cause-and-effect relationship between M .
costalis and the death of Crassostrea virginica has not been experi1959
1960
H O G I S L A N D BAY
JAN
FEB MAR APR MAY JUN J U L AUG SEP OCT NOV DEC
FIG. 55. Death rates of native seaside oysters, Crassostrea virginica, in trays resulting
from parasitism by Minchinia costalw. Each point represents the monthly death
rate for the preceding interval. (After Andrews et al., 1962.)
mentally demonstrated, the high mortality data presented by Andrews
et al. (1962) among parasitized oysters strongly suggest that this
parasite is a pathogen. These data are particularly convincing since the
number of deaths is remarkably greater during the warm months than
during those months when M . costalis cannot be found in oysters.
Moreover, the mortality rate is significantly higher when M . costalis is
present than those associated with other endemic pathogens.