248
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
stylet not seen (but may be present) ; another group of smaller glands
with long ducts immediately in front of ventral sucker (Lebour considered these to be cytogenous glands but this is doubtful); ventral
sucker near middle of body, about same size as anterior sucker or slightly
smaller ; excretory vesicle epitheloid and oval.
Life cycle. The life cycle of C. neptuneae has not been determined
although Lebour (19ll)has stated that it maybe the larva of anAZlocreadium or Lebouria (= Plagioporus), both of which are known to include
representatives which are intestinal parasites of fish.
Pathology. Lebour (1911) has pointed out that the entire whorl of
both species of molluscan hosts is packed with rediae and that the
reproductive organs are destroyed.
34. Cercaria ophicerca Palombi, 1934. (Figs. 157 and 158)
(Superorder Epitheliocystidia; order Plagiorchiida; suborder Plagiorchiata;
Cercaria ophicerca, developing in sporocysts, was described by
Palombi (1934a) from the visceral mass of Tapes decussatus and T .
aureus in the Gulf of Naples. He tentatively placed it in the family
Allocreadiidae.
Sporocyst (Fig. 157) sacciform,
semi-transparent, whitish in color, 1.07 mm long, 0.13 mrn wide.
Cercaria (Fig. 158) with elongate body, averaging 0.34 mm long,
0.09 mm wide, 0.08 mm thick ; cuticle spinous ; anterior sucker averaging
0.05 mm in diameter; ventral sucker averaging 0’05 mm in diameter ; cephalic glands (referred to as “ glandole cistogene ” by
Palombi) on each side of esophagus (Palombi depicts four glands
on each side) which empty to exterior at anterior end of body
via separate ducts ; one pair of eye-spots present, one on each side of
prepharynx ; prepharynx, pharynx, and long esophagus present ;
intestinal caeca terminating at posterior end of body ; two testes,
tandemly arranged in posterior half of body, between ventral sucker
and ovoid epitheloid excretory vesicle; tail 1.20 mm long, 0.03 mm
wide, straight and simple tapering, to point posteriorly.
Other information. Palombi (1934a) has reported the occurrence of
a metacercaria in a single specimen of Tapes decussatus collected at
Naples which is morphologically similar to C. ophicerca and which,
according to him, may be the metacercaria of this cercaria but experimental evidence is wanting.
superfamily Allocreadioidea ; family Allocreadiidae? )
Description of stages in mollusc.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
stylet not seen (but may be present) ; another group of smaller glands
with long ducts immediately in front of ventral sucker (Lebour considered these to be cytogenous glands but this is doubtful); ventral
sucker near middle of body, about same size as anterior sucker or slightly
smaller ; excretory vesicle epitheloid and oval.
Life cycle. The life cycle of C. neptuneae has not been determined
although Lebour (19ll)has stated that it maybe the larva of anAZlocreadium or Lebouria (= Plagioporus), both of which are known to include
representatives which are intestinal parasites of fish.
Pathology. Lebour (1911) has pointed out that the entire whorl of
both species of molluscan hosts is packed with rediae and that the
reproductive organs are destroyed.
34. Cercaria ophicerca Palombi, 1934. (Figs. 157 and 158)
(Superorder Epitheliocystidia; order Plagiorchiida; suborder Plagiorchiata;
Cercaria ophicerca, developing in sporocysts, was described by
Palombi (1934a) from the visceral mass of Tapes decussatus and T .
aureus in the Gulf of Naples. He tentatively placed it in the family
Allocreadiidae.
Sporocyst (Fig. 157) sacciform,
semi-transparent, whitish in color, 1.07 mm long, 0.13 mrn wide.
Cercaria (Fig. 158) with elongate body, averaging 0.34 mm long,
0.09 mm wide, 0.08 mm thick ; cuticle spinous ; anterior sucker averaging
0.05 mm in diameter; ventral sucker averaging 0’05 mm in diameter ; cephalic glands (referred to as “ glandole cistogene ” by
Palombi) on each side of esophagus (Palombi depicts four glands
on each side) which empty to exterior at anterior end of body
via separate ducts ; one pair of eye-spots present, one on each side of
prepharynx ; prepharynx, pharynx, and long esophagus present ;
intestinal caeca terminating at posterior end of body ; two testes,
tandemly arranged in posterior half of body, between ventral sucker
and ovoid epitheloid excretory vesicle; tail 1.20 mm long, 0.03 mm
wide, straight and simple tapering, to point posteriorly.
Other information. Palombi (1934a) has reported the occurrence of
a metacercaria in a single specimen of Tapes decussatus collected at
Naples which is morphologically similar to C. ophicerca and which,
according to him, may be the metacercaria of this cercaria but experimental evidence is wanting.
superfamily Allocreadioidea ; family Allocreadiidae? )
Description of stages in mollusc.