6
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
B. Mutualism
Mutualism describes an intimate relationship during which both the
mutualist and the host are metabolically dependent on each other. An
often cited example of mutualism is that relationship between the
cnidarian Chlorohydra viridissima and the green alga Zoochlorella,
which lives in the cytoplasm of the nutritive-muscular cells of the
cnidarian’s gastrodermis.
The alga produces oxygen which
Chlorohydra utilizes, and Zoochlorella makes use of the nitrogenous
waste products of Chlorohydra for its synthetic processes. Thus there
exists interdependency between the mutualist and host. In addition
to this aspect of metabolic dependency, others exist (Muscatine and
Lenhoff, 1965a,b ; Muscatine, 1965).
What appears to be a concise distinction between parasitism and
mutualism has been partially shattered by Smyth’s (1962) viewpoint
that mutualism is actually a specialized form of parasitism during
which some metabolic by-products of the parasite are of value to the
host. Nevertheless, the mutual dependency is a real, recognizable and
obligatory one during mutualistic, but not during parasitic,
relationships.
C. Commensalism
Commensalism describes that type of more or less intimate relationship during which the commensal generally derives physical shelter
from the host, is nourished on foods that are associated but not a part of
the host, and is not metabolically dependent on the host. Literally,
commensalism means “ eating at the same table ”. It is thus a loose
type of relationship and is not an obligatory one. In accepting this
definition, there is no longer a need to have a special category of
inquilinism as defined by Caullery (1952).
One of the best known examples of commensalism is found within
the realms of marine biology. This is the association between certain
species of hermit crabs and sea anemones. The anemone lives on the
shell sheltering the hermit crab, At this location, it benefits directly
in that it has access to the food caught and scattered by the crab. In
return, the crab benefits from the presence of the anemone which aids
in warding off predators. Yet each animal can live without the other.
Not all anemone-hermit crab associations are commensalistic. For
example, Faurot (1910) has shown that the relationship between the
hermit crab Eupagurus prideauxi and the anemone Adamsia palliata
is an obligatory one, since neither of the partners will survive alone.
Here the relationship appears to have developed into a mutualistic one.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
B. Mutualism
Mutualism describes an intimate relationship during which both the
mutualist and the host are metabolically dependent on each other. An
often cited example of mutualism is that relationship between the
cnidarian Chlorohydra viridissima and the green alga Zoochlorella,
which lives in the cytoplasm of the nutritive-muscular cells of the
cnidarian’s gastrodermis.
The alga produces oxygen which
Chlorohydra utilizes, and Zoochlorella makes use of the nitrogenous
waste products of Chlorohydra for its synthetic processes. Thus there
exists interdependency between the mutualist and host. In addition
to this aspect of metabolic dependency, others exist (Muscatine and
Lenhoff, 1965a,b ; Muscatine, 1965).
What appears to be a concise distinction between parasitism and
mutualism has been partially shattered by Smyth’s (1962) viewpoint
that mutualism is actually a specialized form of parasitism during
which some metabolic by-products of the parasite are of value to the
host. Nevertheless, the mutual dependency is a real, recognizable and
obligatory one during mutualistic, but not during parasitic,
relationships.
C. Commensalism
Commensalism describes that type of more or less intimate relationship during which the commensal generally derives physical shelter
from the host, is nourished on foods that are associated but not a part of
the host, and is not metabolically dependent on the host. Literally,
commensalism means “ eating at the same table ”. It is thus a loose
type of relationship and is not an obligatory one. In accepting this
definition, there is no longer a need to have a special category of
inquilinism as defined by Caullery (1952).
One of the best known examples of commensalism is found within
the realms of marine biology. This is the association between certain
species of hermit crabs and sea anemones. The anemone lives on the
shell sheltering the hermit crab, At this location, it benefits directly
in that it has access to the food caught and scattered by the crab. In
return, the crab benefits from the presence of the anemone which aids
in warding off predators. Yet each animal can live without the other.
Not all anemone-hermit crab associations are commensalistic. For
example, Faurot (1910) has shown that the relationship between the
hermit crab Eupagurus prideauxi and the anemone Adamsia palliata
is an obligatory one, since neither of the partners will survive alone.
Here the relationship appears to have developed into a mutualistic one.