328
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
carapace, hardly visible from dorsal surface ; eyes feebly developed,
very small and not visible from above; abdomen large, overlaps
basipodite of legs laterally, completely covers mouth parts anteriorly,
reaching immediately posterior to eyes ; last abdominal segment bent
inwards rather sharply while feeding so that mouth is uncovered;
abdomen deeply hollowed ; thorax hollowed ; numerous long hairs on
edges of abdomen and sternum, between bases of cheliped and on
pleopods. Smallest ovigerous female with carapace 7.5 mm wide ;
numerous eggs carried in cavity formed by hollowed thorax and deeply
hollowed abdomen ; space between sides of abdomen and thorax very
small, well guarded by long fringing hair ; exopodite of second pair of
pleopods long and blade-like, fringed with long and numerous hairs,
fits along inside of gap as far forward as fifth abdominal segment and
gives protection to eggs.
Hard-shelled male with carapace almost circular, 1.9-6.3 mm wide,
for the most part glabrous, light gray or fawn in color, with a conspicuous pattern of pale yellow areas outlined with darker yellow or
yellowish orange ; in larger specimens the yellow areas increase in size
and fuse to cover the greater part of dorsal surface of carapace ; pigmented lines and areas also occur on chelipeds and legs, including
symmetrically placed yellow spots on their ventral surfaces ; frequently
numerous black, occasionally red, chromatophores scattered over body ;
chelipeds hairy, with broad and swollen palms; two rows of setae
beneath chela, with one reaching from base of palm to tip of finger and
other extending on inner surface only slightly beyond immovable
finger, both rows converging distally ; large tooth present near base of
dactylus, fits into slight notch, with small tooth a t both ends, in propodia1 finger; both biting surfaces bear stiff setae, with closely set
spines towards tips of fingers; small teeth of propodial finger and
curved spines from both fingers absent in some ; walking legs somewhat
flattened, extremely hairy, with hairs being plumose ; second leg slightly
longer than third, both extremely hairy; first leg shorter than third,
fourth leg shortest ; short curved dactyli terminate in horny tips ;
abdomen narrow and tapering ; two small transversely ridged chitinous
nodules on fifth thoracic somite which fit into two pockets on sixth
abdominal segment ; copulatory organs large, first appendage bladelike and hairy, with closed groove along inner surface, with numerous
rosette glands around lower portion of groove, second appendage rodshaped with swollen base, with distal stylet almost hairless and without
glands.
Atkins (1958) has reported the occurrence of thin- or soft-shelled
males. She states : " The thin-shelled male has a normal male abdomen,
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
carapace, hardly visible from dorsal surface ; eyes feebly developed,
very small and not visible from above; abdomen large, overlaps
basipodite of legs laterally, completely covers mouth parts anteriorly,
reaching immediately posterior to eyes ; last abdominal segment bent
inwards rather sharply while feeding so that mouth is uncovered;
abdomen deeply hollowed ; thorax hollowed ; numerous long hairs on
edges of abdomen and sternum, between bases of cheliped and on
pleopods. Smallest ovigerous female with carapace 7.5 mm wide ;
numerous eggs carried in cavity formed by hollowed thorax and deeply
hollowed abdomen ; space between sides of abdomen and thorax very
small, well guarded by long fringing hair ; exopodite of second pair of
pleopods long and blade-like, fringed with long and numerous hairs,
fits along inside of gap as far forward as fifth abdominal segment and
gives protection to eggs.
Hard-shelled male with carapace almost circular, 1.9-6.3 mm wide,
for the most part glabrous, light gray or fawn in color, with a conspicuous pattern of pale yellow areas outlined with darker yellow or
yellowish orange ; in larger specimens the yellow areas increase in size
and fuse to cover the greater part of dorsal surface of carapace ; pigmented lines and areas also occur on chelipeds and legs, including
symmetrically placed yellow spots on their ventral surfaces ; frequently
numerous black, occasionally red, chromatophores scattered over body ;
chelipeds hairy, with broad and swollen palms; two rows of setae
beneath chela, with one reaching from base of palm to tip of finger and
other extending on inner surface only slightly beyond immovable
finger, both rows converging distally ; large tooth present near base of
dactylus, fits into slight notch, with small tooth a t both ends, in propodia1 finger; both biting surfaces bear stiff setae, with closely set
spines towards tips of fingers; small teeth of propodial finger and
curved spines from both fingers absent in some ; walking legs somewhat
flattened, extremely hairy, with hairs being plumose ; second leg slightly
longer than third, both extremely hairy; first leg shorter than third,
fourth leg shortest ; short curved dactyli terminate in horny tips ;
abdomen narrow and tapering ; two small transversely ridged chitinous
nodules on fifth thoracic somite which fit into two pockets on sixth
abdominal segment ; copulatory organs large, first appendage bladelike and hairy, with closed groove along inner surface, with numerous
rosette glands around lower portion of groove, second appendage rodshaped with swollen base, with distal stylet almost hairless and without
glands.
Atkins (1958) has reported the occurrence of thin- or soft-shelled
males. She states : " The thin-shelled male has a normal male abdomen,