238
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
26. Himasthla muehlensi Vogel, 1933
(Superorder Anepitheliocystidia; order Echinostoniida; suborder Echinostomata; superfamily Echinostomatoidea; family Echinostomatidae)
Adults of H . muehlensi were originally described by Vogel (1933)
from a human who had eaten many raw small quahaugs (cherry stones),
Mercenaria mercenaria, in New York and later, upon arrival in
Germany, complained of gastrointestinal disturbances. The worms
were passed after treatment with an anthelmintic. Since it is now known
that the definitive hosts of Himasthla spp. acquire their infections from
ingesting metacercariae-harboring pelecypods, it can be assumed that
the metacercaria of H . muehlensi occurs in Mercenaria mercenaria from
the east coast of the United States although it has yet to be found.
The first experimental demonstration of the life cycle in the genus Himasthla
(that of H . puissetensis) supports the opinion of Vogel that the human
species, H . muehlensi, is acquired by eating raw or insufficiently cooked
mollusks. Examination of large numbers of Venus ( =Memenaria) mercenaria,
purchased in the New York market, has failed, however, to disclose the
metacercaria of this species. Whether or not it is distinct from H . quissetensis
remains to be determined.
Later (Stunkard, 1939), he stated that in a letter to Dr. Vogel from
Dr. H. Mendheim of Munchen, Germany, it was suggested that H .
muehlensi might be a synonym of H . elonqata. However, Stunkard,
after examining Vogel’s specimens of H . muehlensi, stated :
Although they are very similar, specimens of H . muehlelzsi may be distinguished from those of H . puissetensis. The principal difference is the shape
of the testes; in the former species the contour is always smooth whereas in
the latter one, these organs are invariably notched or lobed. It seems unlikely
that such a character would be dependent upon development in a particular
host. Moreover, there are important reasons for considering H . muehlensi
distinct from H. elongata. The two species are very different in size and in
measurements of particular organs. The number of cephalic spines is regarded
as one of the best specific criteria, and H . elongata bears twenty-nine of these
spines whereas the number of H . muehlensi is certainly greater. Reexamination of the material has led both Dr. Vogel and myself to the opinion that
the specific number of spines in H . muehlensi is probably thirty-one, rather
than thirty-two as stated previously.
Since H . quissetensis also bears thirty-one collar spines, it still
remains uncertain, despite Stunkard’s observations on the shape of the
testes, as to whether H . muehlensi should be considered a distinct
species, but until further evidence becomes available, i t will be considered as such.
Stunkard (1938), in reference to H. muehzensi, has stated :
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
26. Himasthla muehlensi Vogel, 1933
(Superorder Anepitheliocystidia; order Echinostoniida; suborder Echinostomata; superfamily Echinostomatoidea; family Echinostomatidae)
Adults of H . muehlensi were originally described by Vogel (1933)
from a human who had eaten many raw small quahaugs (cherry stones),
Mercenaria mercenaria, in New York and later, upon arrival in
Germany, complained of gastrointestinal disturbances. The worms
were passed after treatment with an anthelmintic. Since it is now known
that the definitive hosts of Himasthla spp. acquire their infections from
ingesting metacercariae-harboring pelecypods, it can be assumed that
the metacercaria of H . muehlensi occurs in Mercenaria mercenaria from
the east coast of the United States although it has yet to be found.
The first experimental demonstration of the life cycle in the genus Himasthla
(that of H . puissetensis) supports the opinion of Vogel that the human
species, H . muehlensi, is acquired by eating raw or insufficiently cooked
mollusks. Examination of large numbers of Venus ( =Memenaria) mercenaria,
purchased in the New York market, has failed, however, to disclose the
metacercaria of this species. Whether or not it is distinct from H . quissetensis
remains to be determined.
Later (Stunkard, 1939), he stated that in a letter to Dr. Vogel from
Dr. H. Mendheim of Munchen, Germany, it was suggested that H .
muehlensi might be a synonym of H . elonqata. However, Stunkard,
after examining Vogel’s specimens of H . muehlensi, stated :
Although they are very similar, specimens of H . muehlelzsi may be distinguished from those of H . puissetensis. The principal difference is the shape
of the testes; in the former species the contour is always smooth whereas in
the latter one, these organs are invariably notched or lobed. It seems unlikely
that such a character would be dependent upon development in a particular
host. Moreover, there are important reasons for considering H . muehlensi
distinct from H. elongata. The two species are very different in size and in
measurements of particular organs. The number of cephalic spines is regarded
as one of the best specific criteria, and H . elongata bears twenty-nine of these
spines whereas the number of H . muehlensi is certainly greater. Reexamination of the material has led both Dr. Vogel and myself to the opinion that
the specific number of spines in H . muehlensi is probably thirty-one, rather
than thirty-two as stated previously.
Since H . quissetensis also bears thirty-one collar spines, it still
remains uncertain, despite Stunkard’s observations on the shape of the
testes, as to whether H . muehlensi should be considered a distinct
species, but until further evidence becomes available, i t will be considered as such.
Stunkard (1938), in reference to H. muehzensi, has stated :