280
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
2. Odostomia bisutularis Say, 1922. (Figs. 182 and 183)
(Class Gastropoda; subclass Opisthobranchia; order Tectibranchia; family
Odostomia bisutularis, also referred to as Menestho bisutularis or 0.
( M . ) bisutularis, has been reported by Loosanoff (1956) to be a parasite
of Crassostrea virginica a t Milford, Connecticut.
Description. About 5-7 mm long, some smaller ; shell dull white,
with a thin brownish periostracum ; with seven or eight whorls ; somewhat flattened and slightly shouldered at sutures; with a deeply
impressed revolving line on upper part of each volution ; aperture oval ;
columella bears one oblique fold ; operculum brown and horny.
Ecology. 0. bisutularis is commonly found on sandy mud flats
ranging from the Gulf of St. Lawrence to Florida.
Loosanoff (1956) has stated that this gastropod shows a preference
for young oysters, especially those found in shallow waters.
Boss and Merrill (1965) have studied host-preference by 0. bisutuEaris. By permitting specimens removed from Crassostrea virginica
collected near West Dennis, Massachusetts, to choose between the
oyster and Crepidula fornicata, it was demonstrated that after 2 weeks,
of eighteen 0. bisutularis, three became attached to C. virginica and
the remainder were free on the substrate. In another experiment
during which specimens of C. fornicata were placed between 0. bisutularis
and its original host, C. virginica, so that the parasite had to by-pass
C. fornicata in order to reach oysters, it was found that after 2 days of
the twelve 0. bisutularis tested, two became attached to C. virginica,
two to C. fornicata, and eight were on the substrate. I n another series
of experiments, specimens of 0. bisutularis were given a choice between
C. virginica, Mercenaria mercenaria, Aequipecten irradians, Crepidula
fornicata, C. plana, Crucibulum striatum, Modiolus rnodiolus, Arctica
islandica and Placopecten magellanicus in different combinations. It
was demonstrated that this parasite will become attached to all of the
host species except C. plana, but it showed a behavioral preference
for A. irradians, sometimes even to the point of ignoring its original
host, C. virginica. From these studies, Boss and Merrill have concluded
that although “ trends towards host-specificity are present and detectable, but some measure of non-specificity is retained.” They also
have found that 0. bisutularis does spend considerable time off of hosts.
Pathology. This is one of two species of Odostomia which has been
reported to cause serious damage to their hosts. As more becomes
known about other species, similar deleterious effects will probably be
found. Relative to 0. bisutuhris, Loosanoff has stated :
Pyramidellidae )
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
2. Odostomia bisutularis Say, 1922. (Figs. 182 and 183)
(Class Gastropoda; subclass Opisthobranchia; order Tectibranchia; family
Odostomia bisutularis, also referred to as Menestho bisutularis or 0.
( M . ) bisutularis, has been reported by Loosanoff (1956) to be a parasite
of Crassostrea virginica a t Milford, Connecticut.
Description. About 5-7 mm long, some smaller ; shell dull white,
with a thin brownish periostracum ; with seven or eight whorls ; somewhat flattened and slightly shouldered at sutures; with a deeply
impressed revolving line on upper part of each volution ; aperture oval ;
columella bears one oblique fold ; operculum brown and horny.
Ecology. 0. bisutularis is commonly found on sandy mud flats
ranging from the Gulf of St. Lawrence to Florida.
Loosanoff (1956) has stated that this gastropod shows a preference
for young oysters, especially those found in shallow waters.
Boss and Merrill (1965) have studied host-preference by 0. bisutuEaris. By permitting specimens removed from Crassostrea virginica
collected near West Dennis, Massachusetts, to choose between the
oyster and Crepidula fornicata, it was demonstrated that after 2 weeks,
of eighteen 0. bisutularis, three became attached to C. virginica and
the remainder were free on the substrate. In another experiment
during which specimens of C. fornicata were placed between 0. bisutularis
and its original host, C. virginica, so that the parasite had to by-pass
C. fornicata in order to reach oysters, it was found that after 2 days of
the twelve 0. bisutularis tested, two became attached to C. virginica,
two to C. fornicata, and eight were on the substrate. I n another series
of experiments, specimens of 0. bisutularis were given a choice between
C. virginica, Mercenaria mercenaria, Aequipecten irradians, Crepidula
fornicata, C. plana, Crucibulum striatum, Modiolus rnodiolus, Arctica
islandica and Placopecten magellanicus in different combinations. It
was demonstrated that this parasite will become attached to all of the
host species except C. plana, but it showed a behavioral preference
for A. irradians, sometimes even to the point of ignoring its original
host, C. virginica. From these studies, Boss and Merrill have concluded
that although “ trends towards host-specificity are present and detectable, but some measure of non-specificity is retained.” They also
have found that 0. bisutularis does spend considerable time off of hosts.
Pathology. This is one of two species of Odostomia which has been
reported to cause serious damage to their hosts. As more becomes
known about other species, similar deleterious effects will probably be
found. Relative to 0. bisutuhris, Loosanoff has stated :
Pyramidellidae )