74
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
thus suggesting phylogenetic significance. It should be pointed out
that Tyler made no attempts to determine whether the agglutinations
were brought about by a protein or proteins in the molluscan fluids.
Along similar lines, Johnson (1964) has reported that saline extracts
of the butter clam, Saxidomus giganteus, will agglutinate human
erythrocytes of the phenotypes A, and A,B only. Adsorption experiments revealed that the naturally occurring hemagglutinin can be
completely adsorbed by A, and A,B cells, partially adsorbed by A,
cells, but is unaffected by B and 0 cells. This agglutinin is nondialyzable and is thus probably a large molecule. Moreover, it is
inactivated when the extract is heated to 70°C for 20min, thus
indicating that it is most probably a protein. A similar natural
agglutinin has been reported by Boyd and Brown (1965) in the body
fluids of the land snail Otala (Helix) lactea. This agglutinin, when
tested against various phenotypic human erythrocytes, only agglutinates those of the A type. Cushing et al. (1963) have demonstrated that
the plasma of Octopus bimaculatus will not agglutinate human
erythrocytes carrying A, B, 0, M and N antigens; however, it will
partially inhibit commercial anti-A serum with respect to its reaction
with type A cells. On the other hand, the plasma will not inhibit
anti-B, anti-M, anti-N, and anti-H sera. It would thus appear that the
naturally occurring molluscan agglutinins cited above all portray some
degree of specificity. The possible value of these agglutinins to the
molluscs possessing them is unknown.
The most recent evidence suggesting the possible existence of innate
humoral factors has been contributed by Heyneman (1966) who has
succeeded in demonstrating that larval trematodes transplanted from
natural host to natural host will continue to develop normally, while
larvae transplanted into incompatible hosts will fail to become established. These studies suggest the occurrence of a factor or factors in
incompatible hosts which act against the establishment of the parasites.
Furthermore, as Heyneman has stated :
“The conclusion reached is that resistance to larva1 trematode development
in the incorrect snail host is a physiological rejection within snail tissues
distinct from factors responsible for failure of miracidia to attach to or
penetrate the body wall of the nonadapted host.”
All the information cited above suggests the existence of innate
humoral factors in molluscs ; however, an equal number of investigators
have reported the absence of such factors in other molluscan species.
For example, Dungern (1903) and Cantacuzene (1923) have reported
that natural precipitins and complements cannot be detected in
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
thus suggesting phylogenetic significance. It should be pointed out
that Tyler made no attempts to determine whether the agglutinations
were brought about by a protein or proteins in the molluscan fluids.
Along similar lines, Johnson (1964) has reported that saline extracts
of the butter clam, Saxidomus giganteus, will agglutinate human
erythrocytes of the phenotypes A, and A,B only. Adsorption experiments revealed that the naturally occurring hemagglutinin can be
completely adsorbed by A, and A,B cells, partially adsorbed by A,
cells, but is unaffected by B and 0 cells. This agglutinin is nondialyzable and is thus probably a large molecule. Moreover, it is
inactivated when the extract is heated to 70°C for 20min, thus
indicating that it is most probably a protein. A similar natural
agglutinin has been reported by Boyd and Brown (1965) in the body
fluids of the land snail Otala (Helix) lactea. This agglutinin, when
tested against various phenotypic human erythrocytes, only agglutinates those of the A type. Cushing et al. (1963) have demonstrated that
the plasma of Octopus bimaculatus will not agglutinate human
erythrocytes carrying A, B, 0, M and N antigens; however, it will
partially inhibit commercial anti-A serum with respect to its reaction
with type A cells. On the other hand, the plasma will not inhibit
anti-B, anti-M, anti-N, and anti-H sera. It would thus appear that the
naturally occurring molluscan agglutinins cited above all portray some
degree of specificity. The possible value of these agglutinins to the
molluscs possessing them is unknown.
The most recent evidence suggesting the possible existence of innate
humoral factors has been contributed by Heyneman (1966) who has
succeeded in demonstrating that larval trematodes transplanted from
natural host to natural host will continue to develop normally, while
larvae transplanted into incompatible hosts will fail to become established. These studies suggest the occurrence of a factor or factors in
incompatible hosts which act against the establishment of the parasites.
Furthermore, as Heyneman has stated :
“The conclusion reached is that resistance to larva1 trematode development
in the incorrect snail host is a physiological rejection within snail tissues
distinct from factors responsible for failure of miracidia to attach to or
penetrate the body wall of the nonadapted host.”
All the information cited above suggests the existence of innate
humoral factors in molluscs ; however, an equal number of investigators
have reported the absence of such factors in other molluscan species.
For example, Dungern (1903) and Cantacuzene (1923) have reported
that natural precipitins and complements cannot be detected in