5 . THE PHYLUM PROTOZOA
187
Ecology. MacKinnon and Hawes (1961) have noted that the motility
of C. mytili is not limited to creeping over its host’s foot. It can also
swim with a rotating movement and thus could infect other hosts in the
vicinity.
Beers (1959)) who has examined aspects of the ecology of C. mytili,
has found that in general each mussel has from ten to thirty ciliates and
about 5% of these are regularly in division. This is true of ciliates on
mussels collected at low tide (mussels out of water) and a t high tide
(mussels submerged), hence no correlation exists between the activities
of the ciliates and the cycles of water propulsion. As a relatively high
percentage of ciliates on any mussel are dividing, yet the total number
of ciliates remains relatively constant, it is believed that ciliates are
probably continuously being lost in the excurrent stream.
That normal reproduction of C . mytili is dependent upon its host,
a strong argument in favor of considering these ciliates to be parasites,
has also been demonstrated. Beers has reported that although ciliates
cultured in vitro feed principally on bacteria and colorless flagellates,
they will only grow and divide in sea water t o which a small amount
of Mytilus blood (about 0.25 ml per 10 ml sea water) is added. The contribution supplied by blood has not been identified.
Beers has also demonstrated that contrary to earlier observations
(Kidder, 1933a) C. mytili has considerable tolerance for sea water when
removed from its host. It is able to survive for 48-72 h at 14°C. Thus
it is well adapted t o live for short periods apart from its host and
hence ensures its maintenance and dissemination in a Mytilus population.
Relative to host-symbiont contact, Beers has suggested that ciliation is an important physical property of the substratum on which C.
mytili lives. I n addition, he has stated that : “ . . . though chemotaxis
no doubt affects significantly its choice of a substratum ”.
Physiology. The physiology of C. mytili has not been studied. It
is of interest to note that MacKinnon and Hawes (1961) have reported
that this ciliate has a marked affinity for neutral red, even in weak
dilutions.
9. Crebricoma koxlofji Chatton and Lwoff, 1950. (Figs. 94 and 95)
(Subclass Holotrichia; order Thigmotrichida; family Ancistrocomidae)
Kozloff (1 946a), while studying ancistrocomid ciliates attached to
the palps and ctenidia of the mussel Mytilus edulis in San Francisco
Bay, California, found a ciliate which he believed to be identical with
Raabe’s (1 934) Hypocomina carinata. Certain features of this ciliate
187
Ecology. MacKinnon and Hawes (1961) have noted that the motility
of C. mytili is not limited to creeping over its host’s foot. It can also
swim with a rotating movement and thus could infect other hosts in the
vicinity.
Beers (1959)) who has examined aspects of the ecology of C. mytili,
has found that in general each mussel has from ten to thirty ciliates and
about 5% of these are regularly in division. This is true of ciliates on
mussels collected at low tide (mussels out of water) and a t high tide
(mussels submerged), hence no correlation exists between the activities
of the ciliates and the cycles of water propulsion. As a relatively high
percentage of ciliates on any mussel are dividing, yet the total number
of ciliates remains relatively constant, it is believed that ciliates are
probably continuously being lost in the excurrent stream.
That normal reproduction of C . mytili is dependent upon its host,
a strong argument in favor of considering these ciliates to be parasites,
has also been demonstrated. Beers has reported that although ciliates
cultured in vitro feed principally on bacteria and colorless flagellates,
they will only grow and divide in sea water t o which a small amount
of Mytilus blood (about 0.25 ml per 10 ml sea water) is added. The contribution supplied by blood has not been identified.
Beers has also demonstrated that contrary to earlier observations
(Kidder, 1933a) C. mytili has considerable tolerance for sea water when
removed from its host. It is able to survive for 48-72 h at 14°C. Thus
it is well adapted t o live for short periods apart from its host and
hence ensures its maintenance and dissemination in a Mytilus population.
Relative to host-symbiont contact, Beers has suggested that ciliation is an important physical property of the substratum on which C.
mytili lives. I n addition, he has stated that : “ . . . though chemotaxis
no doubt affects significantly its choice of a substratum ”.
Physiology. The physiology of C. mytili has not been studied. It
is of interest to note that MacKinnon and Hawes (1961) have reported
that this ciliate has a marked affinity for neutral red, even in weak
dilutions.
9. Crebricoma koxlofji Chatton and Lwoff, 1950. (Figs. 94 and 95)
(Subclass Holotrichia; order Thigmotrichida; family Ancistrocomidae)
Kozloff (1 946a), while studying ancistrocomid ciliates attached to
the palps and ctenidia of the mussel Mytilus edulis in San Francisco
Bay, California, found a ciliate which he believed to be identical with
Raabe’s (1 934) Hypocomina carinata. Certain features of this ciliate