6. THE PHYLA PORIFERA, CNIDARIA AND PLATYHELMINTHES
239
Another aspect of the importance of Himasthla spp. to public health
has been briefly stated (Cheng, 1965a). Back in the 1930s and 1940s,
Dr. N. Hathaway," the university physician at Yale University, conducted a clinical and epidemiological study on the cause of a series of
short-termed (24-36 h) but severe gastrointestinal disturbances in
students who shared one common experience, that of having eaten
raw Mercenaria mercenaria purchased from the New Haven, Connecticut, market, and presumably from the Connecticut coast. Bacteriological tests performed on samples of this clam and on victims failed
to reveal any bacteria which could be responsible. On the other hand,
it wm discovered that M . mercenaria from the Connecticut coast
harbored large numbers of H . quissetensis metacercarial cysts. Subsequent feeding of isolated cysts to volunteers failed to establish
infections or produce the specific clinical symptoms and thus the mystery
remained unsolved.
In 1965, I reported that the tissues of Mercenaria mercenaria
surrounding H . quissentensis cysts undergo chemical change. Among
these changes is the accumulation of short-chained fatty acids, provisionally identified as butyric acid among others. It was postulated
that if sufficient number of clams which include toxic short-chained
fatty acids in their tissues are ingested, gastrointestinal disturbances,
such as that found at Yale, could occur. Although chemical changes in
pelecypods harboring other species of Himasthla have not yet been
examined, there is no reason to believe that a parallel phenomenon
should not occur.
27. Himasthla ambigua Palombi, 1934
(Superorder Anepitheliocystidia; order Echinostomida; suborder Echinostomata; superfamily Echinostomatoidea; family Echinostomatidae)
Only the metacercaria of H . ambigua is known. It was described by
Palombi (1934a) encysted on the branchial lamellae of Tapes decussatus
collected in the Gulf of Naples. The morphology of the metacercaria
suggests that it is a member of the genus Himasthla.
Cyst (Fig. 146) transparent, 0.20 mm in diameter.
Metacercaria (Fig. 147) elongate, with ventrally interrupted collar near
anterior end beset with thirty-two spines ; twenty-eight of these, each
measuring 0.20 mm long, arranged in a curved row, but two small
terminal spines are found on each end behind the others ; body 0.72 mm
long, 0-19 mm wide; anterior sucker 0.065 mm in diameter; ventral
sucker posterior to midlength of body, 0.093 mm in diameter; pre* I am deeply grateful to Dr. Hathaway for sharing his yet unpublished findings with
Description.
me during a visit to New Haven, Connecticut, in 1966.
239
Another aspect of the importance of Himasthla spp. to public health
has been briefly stated (Cheng, 1965a). Back in the 1930s and 1940s,
Dr. N. Hathaway," the university physician at Yale University, conducted a clinical and epidemiological study on the cause of a series of
short-termed (24-36 h) but severe gastrointestinal disturbances in
students who shared one common experience, that of having eaten
raw Mercenaria mercenaria purchased from the New Haven, Connecticut, market, and presumably from the Connecticut coast. Bacteriological tests performed on samples of this clam and on victims failed
to reveal any bacteria which could be responsible. On the other hand,
it wm discovered that M . mercenaria from the Connecticut coast
harbored large numbers of H . quissetensis metacercarial cysts. Subsequent feeding of isolated cysts to volunteers failed to establish
infections or produce the specific clinical symptoms and thus the mystery
remained unsolved.
In 1965, I reported that the tissues of Mercenaria mercenaria
surrounding H . quissentensis cysts undergo chemical change. Among
these changes is the accumulation of short-chained fatty acids, provisionally identified as butyric acid among others. It was postulated
that if sufficient number of clams which include toxic short-chained
fatty acids in their tissues are ingested, gastrointestinal disturbances,
such as that found at Yale, could occur. Although chemical changes in
pelecypods harboring other species of Himasthla have not yet been
examined, there is no reason to believe that a parallel phenomenon
should not occur.
27. Himasthla ambigua Palombi, 1934
(Superorder Anepitheliocystidia; order Echinostomida; suborder Echinostomata; superfamily Echinostomatoidea; family Echinostomatidae)
Only the metacercaria of H . ambigua is known. It was described by
Palombi (1934a) encysted on the branchial lamellae of Tapes decussatus
collected in the Gulf of Naples. The morphology of the metacercaria
suggests that it is a member of the genus Himasthla.
Cyst (Fig. 146) transparent, 0.20 mm in diameter.
Metacercaria (Fig. 147) elongate, with ventrally interrupted collar near
anterior end beset with thirty-two spines ; twenty-eight of these, each
measuring 0.20 mm long, arranged in a curved row, but two small
terminal spines are found on each end behind the others ; body 0.72 mm
long, 0-19 mm wide; anterior sucker 0.065 mm in diameter; ventral
sucker posterior to midlength of body, 0.093 mm in diameter; pre* I am deeply grateful to Dr. Hathaway for sharing his yet unpublished findings with
Description.
me during a visit to New Haven, Connecticut, in 1966.