334
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
reveal metabolic dependency, as is suspected in the case of Pinnotheres
ostreum, P. maculatus and P. pisum, then these pinnotherids should
be considered as parasites. For further information, especially the
descriptions of these species, Rathbun’s monograph should be consulted.
Sakai (1965), in his monograph on the crabs of Sagami Bay, has
listed those species of pinnotherid crabs commonly found in commercially important molluscs in the Far East. These are also included in
Table XVIII. References to the descriptions of these species, along with
notes on their natural history, can be found in Sakai’s monograph.
Since the appearance of Rathbun’s monograph, several authors
have reported the occurrence of immature Pinnixa fuba and P. littoralis
associated with various species of pelecypods, including some
commerically important ones. Although the relationship between these
two species of crabs and their molluscan hosts has not been demonstrated to be a parasitic one, such accounts are being briefly mentioned
for those interested in crabs associated with commerically important
marine molluscs.
Pearce (1966a) has reported that the adults of both P. faba and P .
littoralis are sympatrically distributed with their clam host, Tresus
capax, in Puget Sound, State of Washington, but are never associated
with the closely related clam T . nutalli. Furthermore, he has confirmed
the observations of others that immature specimens of both of these
crabs are found within the mantle cavities of a number of pelecypods.
Specifically, Pearce has confirmed Rathbun’s (1918) report that immature P. faba and P. littoralis have been found in Mya arenaria,
Tapes, Saxidomus, Macoma nasuta and “ cockles ”, and Wells’s (1928,
1940) reports that the young of P. littoralis can occur in Macoma
nasuta, M . inquinuta, M . indentata, M . secta, Mya arenaria, Saxidomus
giganteus and Clinocardium nuttalli. It should be mentioned that in
addition to immature specimens, Wells (1940) has also reported the
occurrence of both P. faba and P. littoralis adults in small specimens of
Macoma, Mya and Cardium on rare occasions. It would appear from
such observations that both P. faba and P. littoralis may undergo a
change in host as is the case with Pinnotheres pisum.
In another paper (Pearce, 1966b), it has been reported that the
post-planktonic stages of Fabia subquadrata occurs in the mantle
cavity of the horse mussel, Modiolus modiolus, collected from the
San Juan Archipelago in the State of Washington. Pearce not only
has given a detailed description of the ecology, mating habits, and
growth of this crab, but also has considered it a true parasite, basing
his opinion on the fact that F. subquadrata causes extensive damage to
the gills, palps, and mantle of its host.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
reveal metabolic dependency, as is suspected in the case of Pinnotheres
ostreum, P. maculatus and P. pisum, then these pinnotherids should
be considered as parasites. For further information, especially the
descriptions of these species, Rathbun’s monograph should be consulted.
Sakai (1965), in his monograph on the crabs of Sagami Bay, has
listed those species of pinnotherid crabs commonly found in commercially important molluscs in the Far East. These are also included in
Table XVIII. References to the descriptions of these species, along with
notes on their natural history, can be found in Sakai’s monograph.
Since the appearance of Rathbun’s monograph, several authors
have reported the occurrence of immature Pinnixa fuba and P. littoralis
associated with various species of pelecypods, including some
commerically important ones. Although the relationship between these
two species of crabs and their molluscan hosts has not been demonstrated to be a parasitic one, such accounts are being briefly mentioned
for those interested in crabs associated with commerically important
marine molluscs.
Pearce (1966a) has reported that the adults of both P. faba and P .
littoralis are sympatrically distributed with their clam host, Tresus
capax, in Puget Sound, State of Washington, but are never associated
with the closely related clam T . nutalli. Furthermore, he has confirmed
the observations of others that immature specimens of both of these
crabs are found within the mantle cavities of a number of pelecypods.
Specifically, Pearce has confirmed Rathbun’s (1918) report that immature P. faba and P. littoralis have been found in Mya arenaria,
Tapes, Saxidomus, Macoma nasuta and “ cockles ”, and Wells’s (1928,
1940) reports that the young of P. littoralis can occur in Macoma
nasuta, M . inquinuta, M . indentata, M . secta, Mya arenaria, Saxidomus
giganteus and Clinocardium nuttalli. It should be mentioned that in
addition to immature specimens, Wells (1940) has also reported the
occurrence of both P. faba and P. littoralis adults in small specimens of
Macoma, Mya and Cardium on rare occasions. It would appear from
such observations that both P. faba and P. littoralis may undergo a
change in host as is the case with Pinnotheres pisum.
In another paper (Pearce, 1966b), it has been reported that the
post-planktonic stages of Fabia subquadrata occurs in the mantle
cavity of the horse mussel, Modiolus modiolus, collected from the
San Juan Archipelago in the State of Washington. Pearce not only
has given a detailed description of the ecology, mating habits, and
growth of this crab, but also has considered it a true parasite, basing
his opinion on the fact that F. subquadrata causes extensive damage to
the gills, palps, and mantle of its host.