332
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
Description. Adult female (Fig. 222) with soft exoskeleton, carapace
rounded quadrangular, 12-13 mm in length and width, with markedly
deflexed front; with four pairs of ambulatory legs, with the second
being the longest ; row of long hair on carpi and propodi in very young
specimens, disappears in full-grown ones ; dactyli of all legs very short
and uniformly hook-shaped ; dactylus of external maxilliped styliform
with tip exceeding that of propodus.
Adult male (Fig. 223) smaller than female, with well-calcified body ;
carapace circular, about 9 mm in length and nearly 9 mm in width ;
dorsal surface strikingly convex, frontal edge thick, produced anteriorly,
slightly emarginated in middle ; of four pairs of ambulatory legs, the
second is longest; carpi with an oblique row of very long, featherlike
hairs ; propodi with a row of similar hairs along anterior border ; dactylus
of external maxilliped styliform as in female.
Other information. According to Sakai (1965), during the mat,ing
season, which occurs in early summer in Japan, both the male and female
are usually seen together within the same mollusc's mantle cavity.
This would suggest that unlike the three species of Pinnotheres discussed previously, neither the male nor both the male and female leave
the pelecypod.
5. Other Pinnotherid Grabs
Rathbun (1918), in her definitive treatise of the grapsoid crabs of
America which includes the Pinnotheridae, has listed twenty-seven
species of the genus Pinnotheres. Of these, she lists seven which are
" commensals " of commercially important pelecypods (Table XVIII).
No host is listed for ten other species, while the remaining ten are
listed as " commensals '' of other types of invertebrates. Among the
four species of Fabia listed, one is noted as a " commensal '' of Tapes
and other pelecypods, while another, F . subquadrata, is listed as a
" commensal " of " bivalved molluscs ". Of the five species of Parapinnixa and seven species of Dissodactylus, she lists none to be associated
with a pelecypod. Of the twenty-six species of Pinnixa, she lists
two species as being " commensals '' of commercially important molluscs
(Table XVIII). The monotypic genera Xcleroplax, Tetrias and Pinnotherelia are reported not to include symbionts as is the case among the
three species of Pinnaxodes. The single species of Opisthopus, 0.
transversus, is said to be a " commensal of Mytilus edulis ".
The relationships between the eleven species of pinnotherid crabs
listed by Rathbun as occurring in the mantle cavities of commercially
important molluscs have not been investigated. If futuro studies should
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
Description. Adult female (Fig. 222) with soft exoskeleton, carapace
rounded quadrangular, 12-13 mm in length and width, with markedly
deflexed front; with four pairs of ambulatory legs, with the second
being the longest ; row of long hair on carpi and propodi in very young
specimens, disappears in full-grown ones ; dactyli of all legs very short
and uniformly hook-shaped ; dactylus of external maxilliped styliform
with tip exceeding that of propodus.
Adult male (Fig. 223) smaller than female, with well-calcified body ;
carapace circular, about 9 mm in length and nearly 9 mm in width ;
dorsal surface strikingly convex, frontal edge thick, produced anteriorly,
slightly emarginated in middle ; of four pairs of ambulatory legs, the
second is longest; carpi with an oblique row of very long, featherlike
hairs ; propodi with a row of similar hairs along anterior border ; dactylus
of external maxilliped styliform as in female.
Other information. According to Sakai (1965), during the mat,ing
season, which occurs in early summer in Japan, both the male and female
are usually seen together within the same mollusc's mantle cavity.
This would suggest that unlike the three species of Pinnotheres discussed previously, neither the male nor both the male and female leave
the pelecypod.
5. Other Pinnotherid Grabs
Rathbun (1918), in her definitive treatise of the grapsoid crabs of
America which includes the Pinnotheridae, has listed twenty-seven
species of the genus Pinnotheres. Of these, she lists seven which are
" commensals " of commercially important pelecypods (Table XVIII).
No host is listed for ten other species, while the remaining ten are
listed as " commensals '' of other types of invertebrates. Among the
four species of Fabia listed, one is noted as a " commensal '' of Tapes
and other pelecypods, while another, F . subquadrata, is listed as a
" commensal " of " bivalved molluscs ". Of the five species of Parapinnixa and seven species of Dissodactylus, she lists none to be associated
with a pelecypod. Of the twenty-six species of Pinnixa, she lists
two species as being " commensals '' of commercially important molluscs
(Table XVIII). The monotypic genera Xcleroplax, Tetrias and Pinnotherelia are reported not to include symbionts as is the case among the
three species of Pinnaxodes. The single species of Opisthopus, 0.
transversus, is said to be a " commensal of Mytilus edulis ".
The relationships between the eleven species of pinnotherid crabs
listed by Rathbun as occurring in the mantle cavities of commercially
important molluscs have not been investigated. If futuro studies should