6. THE PHYLA PORIFERA, CNIDARIA AND PLATYHELMINTHES
245
Life cycle. Aspects of the life cycle of P. acanthus have been examined
by Linton (1914), F. G. Rees (1939b, 1940), Lebour (1911) and Stunkard
and Cable (1932). The adults may and commonly do include free
miracidia in the terminal portion of their uteri although eggs are also
laid containing fully developed miracidia. These hatch in 0ea water
after being voided in the avian host’s feces. The miracidium, either
born free or hatching from the egg, penetrates the first intermediate
host, Nucella lapillus in British waters, Urosalrpinx cinerea in addition
to Nucella lapillus in northeastern United States, and Littorina pintado
in Hawaii.* Each miracidium contains a mother redia. Within the snail,
mother rediae give rise to daughter rediae which in turn give rise to
cercariae. Cercariae, once out of the first intermediate host, will encyst
on practically any surface and hence a second intermediate host is not
really necessary. Shore birds (Larus argentatus, L. canus, Nycticorax
nycticorax hoactili) most probably become infected with the ingestion
of shellfish with metacercariae attached to their surfaces. Attempts by
Stunkard and Cable (1932) to infect guinea-pigs, rats and mice were
unsuccessful.
32. Neophasis pusilla Stafford, 1904. (Figs. 151-154)
(Superorder Epitheliocysticlia ; order Plagiorchiida ; suborder Plagiorchiata ;
While examining specimens of the buckie, Buccinum undatum,
brought in by the fishing boats from Cullercoats, northeast England,
Lebour (1911) found that 7 % were parasitized by a species of larval
trematode which she associated with an adult form found in the catfish
Anarrhichm lwpus. She designated this trematode aa Acanthopsolus
lageniformis. In addition, she found one specimen of B. undatum collected
at Holy Island, northeast England, parasitizedbylarvaeof this trematode.
Description of stages in mollusc. Older rediae (Fig. 151) pale yellow,
measuring from 0.50 mm long (one specimen depicted by Lebour
measured 3 mm) ; without collar or ambulatory buds ; containing
thirty or more cercariae. Smallest rediae (Fig. 152) about 0.30 mm
long, with pointed posterior terminal, pharynx, and intestinal caecum ;
caecum short and inconspicuous in older rediae. Young cercaria (Fig.
153) with straight tail which is slightly longer than body, apparently
lost prior to emergence from redia. Fully grown cercaria (Fig. 154)
about 0.5 mm long, width less than half body length; oval or flaskshaped, with anterior end more pointed ; body covered with spines
which are more sparse posteriorly ; with two eye-spots, one on each side
superfamily Allocreadioidea ; family Allocreadiidae)
*The Hawaiian species of Parorchis has only been tentatively identified as P .
acalzthua. It may be a subspecies or another species.
245
Life cycle. Aspects of the life cycle of P. acanthus have been examined
by Linton (1914), F. G. Rees (1939b, 1940), Lebour (1911) and Stunkard
and Cable (1932). The adults may and commonly do include free
miracidia in the terminal portion of their uteri although eggs are also
laid containing fully developed miracidia. These hatch in 0ea water
after being voided in the avian host’s feces. The miracidium, either
born free or hatching from the egg, penetrates the first intermediate
host, Nucella lapillus in British waters, Urosalrpinx cinerea in addition
to Nucella lapillus in northeastern United States, and Littorina pintado
in Hawaii.* Each miracidium contains a mother redia. Within the snail,
mother rediae give rise to daughter rediae which in turn give rise to
cercariae. Cercariae, once out of the first intermediate host, will encyst
on practically any surface and hence a second intermediate host is not
really necessary. Shore birds (Larus argentatus, L. canus, Nycticorax
nycticorax hoactili) most probably become infected with the ingestion
of shellfish with metacercariae attached to their surfaces. Attempts by
Stunkard and Cable (1932) to infect guinea-pigs, rats and mice were
unsuccessful.
32. Neophasis pusilla Stafford, 1904. (Figs. 151-154)
(Superorder Epitheliocysticlia ; order Plagiorchiida ; suborder Plagiorchiata ;
While examining specimens of the buckie, Buccinum undatum,
brought in by the fishing boats from Cullercoats, northeast England,
Lebour (1911) found that 7 % were parasitized by a species of larval
trematode which she associated with an adult form found in the catfish
Anarrhichm lwpus. She designated this trematode aa Acanthopsolus
lageniformis. In addition, she found one specimen of B. undatum collected
at Holy Island, northeast England, parasitizedbylarvaeof this trematode.
Description of stages in mollusc. Older rediae (Fig. 151) pale yellow,
measuring from 0.50 mm long (one specimen depicted by Lebour
measured 3 mm) ; without collar or ambulatory buds ; containing
thirty or more cercariae. Smallest rediae (Fig. 152) about 0.30 mm
long, with pointed posterior terminal, pharynx, and intestinal caecum ;
caecum short and inconspicuous in older rediae. Young cercaria (Fig.
153) with straight tail which is slightly longer than body, apparently
lost prior to emergence from redia. Fully grown cercaria (Fig. 154)
about 0.5 mm long, width less than half body length; oval or flaskshaped, with anterior end more pointed ; body covered with spines
which are more sparse posteriorly ; with two eye-spots, one on each side
superfamily Allocreadioidea ; family Allocreadiidae)
*The Hawaiian species of Parorchis has only been tentatively identified as P .
acalzthua. It may be a subspecies or another species.