196
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
spherical), dorsally situated in posterior half of body ; micronucleus,
2.7-4-0 p in diameter, spherical, near middle of body, anterior t o or
to one side of macronucleus ; contractile vacuole centrally located,
opens to exterior on ventral body surface ; cytoplasm with numerous
lipoid droplets ; several food vacuoles in posterior part of body.
Ecology. Kozloff (194613) has found H . mytili on the gills and palps
of about 80% of the specimens of Mytilus edulis from various localities
in San Francisco Bay. It may be the only ciliate present on these
mussels or, more commonly, it is associated with two other ciliates,
Ancistrum mytili and Crebricoma koxlofi.
According to Kozloff, H . mytili is a true parasite since it is nutritionally dependent upon its host. He states : “ The anterior end of the
body is provided with a short contractile tentacle which enables the
ciliate to attach itself to the epithelial cells of the gills and palps of the
host and to suck out their contents.”
Pathology. Although H . mytili is known to feed on the contents of
the epithelial cells of Mytilus edulis, the actual pathological changes
associated with this feeding mechanism, at both the cellular and
organismic levels, have not been studied.
16. Gargarius gargarius Chatton and Lwoff, 1934. (Figs. 105-107)
(Subclass Holotrichia; order Thigmotrichida; family Sphenophryidae)
Gargarius gargarius was originally discovered by Chatton and
Lwoff (1934) attached to the gills of Mytilus edulis. It was redescribed
by Raabe (1938) and Chatton and Lwoff (1950).
Description. Body ovoid and dorsoventrally flattened, tapering a t
anterior and posterior ends, more so anteriorly, 25-60 p long, devoid
of cilia ; distinct suctorial tentacle continuous with canal leading to
interior of body ; lateral borders of body lined with blunt, pointed, or
capitate fringed papillae of unknown function ; papillae inserted on
marginal filaments encircling body behind tentacle and further supported
by filaments which pass into endoplasm; macronucleus large and
elongate ; micronucleus large, nearly half the size of macronucleus ; no
contractile vacuole present.
Life cycle. G . gargarius reproduces by budding off a ciliated larva
posteriorly (Fig. 107). The cilia of the daughter arise from its kinetosomes. The suctorial tentacle develops when the daughter is severed
from the parent as are the marginal papillae. It still remains undetermined how individuals are passed from host to host. It is possible that
a free-swimming stage, possibly the larva, exists.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
spherical), dorsally situated in posterior half of body ; micronucleus,
2.7-4-0 p in diameter, spherical, near middle of body, anterior t o or
to one side of macronucleus ; contractile vacuole centrally located,
opens to exterior on ventral body surface ; cytoplasm with numerous
lipoid droplets ; several food vacuoles in posterior part of body.
Ecology. Kozloff (194613) has found H . mytili on the gills and palps
of about 80% of the specimens of Mytilus edulis from various localities
in San Francisco Bay. It may be the only ciliate present on these
mussels or, more commonly, it is associated with two other ciliates,
Ancistrum mytili and Crebricoma koxlofi.
According to Kozloff, H . mytili is a true parasite since it is nutritionally dependent upon its host. He states : “ The anterior end of the
body is provided with a short contractile tentacle which enables the
ciliate to attach itself to the epithelial cells of the gills and palps of the
host and to suck out their contents.”
Pathology. Although H . mytili is known to feed on the contents of
the epithelial cells of Mytilus edulis, the actual pathological changes
associated with this feeding mechanism, at both the cellular and
organismic levels, have not been studied.
16. Gargarius gargarius Chatton and Lwoff, 1934. (Figs. 105-107)
(Subclass Holotrichia; order Thigmotrichida; family Sphenophryidae)
Gargarius gargarius was originally discovered by Chatton and
Lwoff (1934) attached to the gills of Mytilus edulis. It was redescribed
by Raabe (1938) and Chatton and Lwoff (1950).
Description. Body ovoid and dorsoventrally flattened, tapering a t
anterior and posterior ends, more so anteriorly, 25-60 p long, devoid
of cilia ; distinct suctorial tentacle continuous with canal leading to
interior of body ; lateral borders of body lined with blunt, pointed, or
capitate fringed papillae of unknown function ; papillae inserted on
marginal filaments encircling body behind tentacle and further supported
by filaments which pass into endoplasm; macronucleus large and
elongate ; micronucleus large, nearly half the size of macronucleus ; no
contractile vacuole present.
Life cycle. G . gargarius reproduces by budding off a ciliated larva
posteriorly (Fig. 107). The cilia of the daughter arise from its kinetosomes. The suctorial tentacle develops when the daughter is severed
from the parent as are the marginal papillae. It still remains undetermined how individuals are passed from host to host. It is possible that
a free-swimming stage, possibly the larva, exists.