G . THE PHYLA PORIFERA. CNIDARIA AND PLATYHELMINTHES
223
about one-sixth size of anterior sucker according to Palombi (although
that of the specimen which he depicted (Fig. 132) appears to be considerably smaller), situated in posterior half of body between caeca ; numerous
glands surround and empty into anterior sucker ; prepharynx absent ;
pharynx large, with its diameter larger than that of ventral sucker ;
esophagus short ; intestinal caeca large and bulbous, occupying middle
portion of body; excretory vesicle Y-shaped with minute stem, arms
reaching level of anterior sucker ; immature testes ovoid, one on each
side of body near posterolateral margins, posterior to caeca; small
immature ovary to the left and overlapping ventral sucker; genital
pore immediately anterior to ventral sucker.
Other information. The cyst wall of this metacercaria is in the form
of a gelatinous capsule within which the metacercaria is not doubled over.
Its presence on the mantle of Mytilus galloprovincialis causes the laying
down of nacrous material in pearl formation.
14. Gymnophallus bursicola Odhner, 1900. (Fig. 133)
(Superorder Anepitheliocystidia; order Strigeatoidea; suborder Azygiata;
Stunkard and Uzmann (1958), as a part of their extensive study on
gymnophallids of northeastern United States, reported the occurrence
of a gymnophallid metacercaria on the mantle of Mytilus edulis
collected a t Milford, Connecticut, and Newburyport, Massachusetts.
This metacercaria was found in 20% of the mussels examined, with one
to ten per mussel. They fed these metacercariae to hamsters and young
eider ducks, Somateria mollissima. Adults were recovered from both
experimental hosts but those from the hamster had not reached maturity
in 7 days while one specimen from an eider duck had just commenced
producing eggs in what was believed to be 10 days. The adults were
tentatively identified as Gymnophallus bursicola, a species described by
Odhner (1900) from the bursa Fabricii of Somateria mollissima in
Sweden, and later reported to occur in Melanitta fusca and M . nigra in
Japan (Yamaguti, 1939). Its life cycle had been reported by Giard
(1907).
Description of metacercaria (the form found in economically important molluscs). Metacercaria ovoid, 0.4-0.6 mm long x 0.2-0.3 mm
wide ; body covered with cuticular spines ; anterior sucker 0.088 mm
in diameter ; prepharynx absent ; pharynx, 0.030 mm in diameter, and
short esophagus present ; intestinal caeca extending to near anterior
margin of ventral sucker ; ventral sucker slightly smaller than anterior
superfamily Fellodistomatoidea; family Fellodistomatidae)
223
about one-sixth size of anterior sucker according to Palombi (although
that of the specimen which he depicted (Fig. 132) appears to be considerably smaller), situated in posterior half of body between caeca ; numerous
glands surround and empty into anterior sucker ; prepharynx absent ;
pharynx large, with its diameter larger than that of ventral sucker ;
esophagus short ; intestinal caeca large and bulbous, occupying middle
portion of body; excretory vesicle Y-shaped with minute stem, arms
reaching level of anterior sucker ; immature testes ovoid, one on each
side of body near posterolateral margins, posterior to caeca; small
immature ovary to the left and overlapping ventral sucker; genital
pore immediately anterior to ventral sucker.
Other information. The cyst wall of this metacercaria is in the form
of a gelatinous capsule within which the metacercaria is not doubled over.
Its presence on the mantle of Mytilus galloprovincialis causes the laying
down of nacrous material in pearl formation.
14. Gymnophallus bursicola Odhner, 1900. (Fig. 133)
(Superorder Anepitheliocystidia; order Strigeatoidea; suborder Azygiata;
Stunkard and Uzmann (1958), as a part of their extensive study on
gymnophallids of northeastern United States, reported the occurrence
of a gymnophallid metacercaria on the mantle of Mytilus edulis
collected a t Milford, Connecticut, and Newburyport, Massachusetts.
This metacercaria was found in 20% of the mussels examined, with one
to ten per mussel. They fed these metacercariae to hamsters and young
eider ducks, Somateria mollissima. Adults were recovered from both
experimental hosts but those from the hamster had not reached maturity
in 7 days while one specimen from an eider duck had just commenced
producing eggs in what was believed to be 10 days. The adults were
tentatively identified as Gymnophallus bursicola, a species described by
Odhner (1900) from the bursa Fabricii of Somateria mollissima in
Sweden, and later reported to occur in Melanitta fusca and M . nigra in
Japan (Yamaguti, 1939). Its life cycle had been reported by Giard
(1907).
Description of metacercaria (the form found in economically important molluscs). Metacercaria ovoid, 0.4-0.6 mm long x 0.2-0.3 mm
wide ; body covered with cuticular spines ; anterior sucker 0.088 mm
in diameter ; prepharynx absent ; pharynx, 0.030 mm in diameter, and
short esophagus present ; intestinal caeca extending to near anterior
margin of ventral sucker ; ventral sucker slightly smaller than anterior
superfamily Fellodistomatoidea; family Fellodistomatidae)