224
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
sucker ; testicular anlage in posterior half of body, one on each side of
ventral sucker ; ovarial anlagen, if present, immediately anterior to
left testis; with cephalic glands (exact number not known) on each
side of pharynx ; genital pore near anterior margin of ventral sucker ;
genital atrium, if present, tubular ; excretory vesicle Y-shaped, with
arms reaching level of pharynx anteriorly.
Other information. Stunkard and Uzmann (1958) have noted that
the metacercariae produce lesions in the mantle and body wall of
Mytilus edulis which may result in the deposition of nacrous material.
15. Metacercaria (Gymnophalloides) tokiensis Fujita, 1925. (Fig. 134)
(Superorder Anepitheliocystidia; order Strigeatoidea; suborder Azygiata;
This metacercaria was described by Fujita (1925) on the external
surface of the mantle of Crassostrea gigas from Hokkaido, Matsushima
Bay, Tokyo Bay, Hamana Lake and Ise Bay, Japan.
Body elongate ovoid, pointed posteriorly, 0.36 mm
long x 0.23 mm wide, covered with sparsely arranged minute papillalike projections ; with two eye-spots on ventral surface overlapping
intestinal caeca ; anterior sucker 0.13 mm x 0.09 mm ; ventral sucker,
0.05 mm x 0.06 mm, in posterior one-third of body; prepharynx
absent ; pharynx 0.02 mm long ; esophagus short ; intestinal caeca
bulbous, measuring 0.08 x 0.04 mm, reaching midlength of body or
slightly beyond ; two testes, each measuring 0425mm ingreatest length,
one on each side of ventral sucker ; ovary slightly larger than testes,
anterior to left testis and lateral to intestinal caecum ; seminal vesicle,
seminal receptacle, ootype, Laurer's canal, and cirrus (ejaculatory
duct) present ; genital pore on ventral surface, approximately midway
between ventral sucker and caecal bifurcation ; vitelline glands
scattered in parenchyma on each side of body, extending along entire
length of body ; excretory vesicle Y-shaped, with extremely short stem
and large arms which reach level of anterior sucker.
Physiology. Fujita (1925) has shown that this metacercaria is very
sensitive to changes in the density (" densiti: ") of the surrounding
water. At 20°C, if the water has a density of 1.024, the parasites will
live for 5 h but if the density is increased to 1.026, the longevity of the
metacercaria is reduced to 30 min. Similarly, at water densities of
1.028 and 1.030, the survival periods are reduced to 15 and 10 min
respectively.
superfamily Fellodistomatoidea; family Fellodistomatidae)
Description.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
sucker ; testicular anlage in posterior half of body, one on each side of
ventral sucker ; ovarial anlagen, if present, immediately anterior to
left testis; with cephalic glands (exact number not known) on each
side of pharynx ; genital pore near anterior margin of ventral sucker ;
genital atrium, if present, tubular ; excretory vesicle Y-shaped, with
arms reaching level of pharynx anteriorly.
Other information. Stunkard and Uzmann (1958) have noted that
the metacercariae produce lesions in the mantle and body wall of
Mytilus edulis which may result in the deposition of nacrous material.
15. Metacercaria (Gymnophalloides) tokiensis Fujita, 1925. (Fig. 134)
(Superorder Anepitheliocystidia; order Strigeatoidea; suborder Azygiata;
This metacercaria was described by Fujita (1925) on the external
surface of the mantle of Crassostrea gigas from Hokkaido, Matsushima
Bay, Tokyo Bay, Hamana Lake and Ise Bay, Japan.
Body elongate ovoid, pointed posteriorly, 0.36 mm
long x 0.23 mm wide, covered with sparsely arranged minute papillalike projections ; with two eye-spots on ventral surface overlapping
intestinal caeca ; anterior sucker 0.13 mm x 0.09 mm ; ventral sucker,
0.05 mm x 0.06 mm, in posterior one-third of body; prepharynx
absent ; pharynx 0.02 mm long ; esophagus short ; intestinal caeca
bulbous, measuring 0.08 x 0.04 mm, reaching midlength of body or
slightly beyond ; two testes, each measuring 0425mm ingreatest length,
one on each side of ventral sucker ; ovary slightly larger than testes,
anterior to left testis and lateral to intestinal caecum ; seminal vesicle,
seminal receptacle, ootype, Laurer's canal, and cirrus (ejaculatory
duct) present ; genital pore on ventral surface, approximately midway
between ventral sucker and caecal bifurcation ; vitelline glands
scattered in parenchyma on each side of body, extending along entire
length of body ; excretory vesicle Y-shaped, with extremely short stem
and large arms which reach level of anterior sucker.
Physiology. Fujita (1925) has shown that this metacercaria is very
sensitive to changes in the density (" densiti: ") of the surrounding
water. At 20°C, if the water has a density of 1.024, the parasites will
live for 5 h but if the density is increased to 1.026, the longevity of the
metacercaria is reduced to 30 min. Similarly, at water densities of
1.028 and 1.030, the survival periods are reduced to 15 and 10 min
respectively.
superfamily Fellodistomatoidea; family Fellodistomatidae)
Description.