6. THE PHYLA PORIFERA, CNIDARIA AND PLATYHELMINTHES
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11. Phylum CNIDARIA
Most of the cnidarians known to be associated with marine molluscs
are epiphoronts" ; however, four species of the genus Eugymnanthea
have been reported as " commensals " found within the mantle cavities
of commercially important pelecypods (see Crowell, 1957). Until more
information on the relationship between these hydroids and their hosts
becomes available, these are only briefly mentioned herein.
The first of the fourt species, E . inquilina, was described by Palombi
(1936a) from within the mantle cavity of Tapes decussatus collected a t
Lago Fusaro, near Naples, Italy. The second, E . polimantii, was
originally described as Mytilhydra polirnantii by Cerruti ( 1941b) from
the mantle cavity of Mytilus galloprovincialis a t Taranto, Italy. The
third species, E. ostrearum, was described by Mattox and Crowell (1951)
from within the mantle cavity of Crassostrea rhizophorae from Boqubron
Lagoon, Puerto Rico. The fourth, E . japonica in Crassostrea gigas in
Japan, was described by Yamada (1950) in a new genus Ostreohydra,
and later transferred to Eugymnanthea by Crowell (1957). All four species
possess a conspicuous rounded basal disk by which the polyps are
enabled t o remain attached to their host's tissues. Furthermore, both a
perisarc and stolons are absent. These features, according to Mattox
and Crowell (1951), may be considered as adaptive to commensalism.
Within their hosts, the polyps are attached to the inner surface of
the mantle but in heavily infested pelecypods, they may also be
attached on the foot, gills and labial palps.
111. Phylum PLATYHELMINTHES
A. Class Turbellaria
Several species of turbellarians have been reported associated with
oommercially important marine molluscs. Among these, several
belonging to the genera Stylochus and Pseudostylochus are known to
feed on oysters and other marine invertebrates. I n accepting the
definition of predation given on pp. 8-9, these turbellarians should be
considered as predators rather than parasites. For this reason, these
turbellarians will not be considered a t any length herein but, for the
convenience of those interested in invertebrates associated with commercially important marine molluscs, the more common species are
briefly mentioned along with citations to the pertinent literature.
*For a review of the types of relationships occurring between cnidarians and
molluscs, see W. J. Rees (1967).
t Crowell (1957) thinks that E. inquilina and E. polimantii are the same species.
lo!)
11. Phylum CNIDARIA
Most of the cnidarians known to be associated with marine molluscs
are epiphoronts" ; however, four species of the genus Eugymnanthea
have been reported as " commensals " found within the mantle cavities
of commercially important pelecypods (see Crowell, 1957). Until more
information on the relationship between these hydroids and their hosts
becomes available, these are only briefly mentioned herein.
The first of the fourt species, E . inquilina, was described by Palombi
(1936a) from within the mantle cavity of Tapes decussatus collected a t
Lago Fusaro, near Naples, Italy. The second, E . polimantii, was
originally described as Mytilhydra polirnantii by Cerruti ( 1941b) from
the mantle cavity of Mytilus galloprovincialis a t Taranto, Italy. The
third species, E. ostrearum, was described by Mattox and Crowell (1951)
from within the mantle cavity of Crassostrea rhizophorae from Boqubron
Lagoon, Puerto Rico. The fourth, E . japonica in Crassostrea gigas in
Japan, was described by Yamada (1950) in a new genus Ostreohydra,
and later transferred to Eugymnanthea by Crowell (1957). All four species
possess a conspicuous rounded basal disk by which the polyps are
enabled t o remain attached to their host's tissues. Furthermore, both a
perisarc and stolons are absent. These features, according to Mattox
and Crowell (1951), may be considered as adaptive to commensalism.
Within their hosts, the polyps are attached to the inner surface of
the mantle but in heavily infested pelecypods, they may also be
attached on the foot, gills and labial palps.
111. Phylum PLATYHELMINTHES
A. Class Turbellaria
Several species of turbellarians have been reported associated with
oommercially important marine molluscs. Among these, several
belonging to the genera Stylochus and Pseudostylochus are known to
feed on oysters and other marine invertebrates. I n accepting the
definition of predation given on pp. 8-9, these turbellarians should be
considered as predators rather than parasites. For this reason, these
turbellarians will not be considered a t any length herein but, for the
convenience of those interested in invertebrates associated with commercially important marine molluscs, the more common species are
briefly mentioned along with citations to the pertinent literature.
*For a review of the types of relationships occurring between cnidarians and
molluscs, see W. J. Rees (1967).
t Crowell (1957) thinks that E. inquilina and E. polimantii are the same species.