292
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
fifth pair as large as third pair, each process is triangular and extends
diagonally outward and backward and with an acute tip which sometimes curves slightly forward ; genital segment enlarged a t posterior
corners but without processes ; abdomen considerably narrower and
thinner than genital segment, tapers slightly posteriorly, as long as
genital segment, undivided and with smooth lateral margins ; caudal
rami cylindrical, longer than wide, slightly divergent, with no setae ;
first antenna of four segments, basal segment large and swollen, all four
sparsely armed with small spines; second antenna of two segments,
distal segment in form of a curved claw, divided a t center and with each
half armed with a spine-like seta ; upper lip subtriangular ; mandible
cylindrical, unsegmented, extremely small ; first maxilla as elliptical
mamma, armed with two short spine-like setae; second maxilla of
stout basal portion and a two-segmented portion with terminal segment
curved and fringed with hairs ; maxilliped lacking in female ; each of
four pairs of uniramous swimming legs reduced to simple pointed
knob; ovisacs elongate conical, 7 mm long; eggs minute, about 200
in each sac.
Adult male (Fig. 191) considerably smaller than female, total length
4 mm, greatest width 0.55 mm ; with thoracic segments more or less
separated by grooves ; thoracic processes more reduced than in female
but more prominent than those of M . intestinalis except for first pair
which is wanting in M . orieatalis ; legs larger than in female but still
as uniramous pointed knobs; abdomen unsegmented ; caudal rami
enlarged and nearly parallel ; mouth parts similar to those of female
but with additional pair of stout maxillipeds behind second maxillae.
Life cycle. The life cycle of M . orientalis is not known although it
is most probably of the same pattern as that of M . intestinalis.
Ecology.* I n their paper in which was reported the occurrence of this
copepod in Mytilus californianus, Chew et al. (1963) also reported that
although the average number of copepods per mussel is not significantly
different in Ostrea lurida (2*4), Mytilus edulis (2-3), and M . californianus
(2.5), those in Ostrea lurida are larger, averaging 6-3 mm in length,
than those in the two species of mussels, with those in mussels ranging
from 3-0 to 4.0 mm. Examination of these copepods has revealed that
the smaller specimens (3.0-4.0 mm) are males while the larger ones
(6.0 mm and longer) are females. Although their samples included only
fifty-two 0. lurida (9.6% infected), twenty-four M . edulis (5893%
infected) and twenty M . californianus (65 yo infected), their finding of
proportionally more males in 0. lurida may be significant.
* See note 011 p. 390.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
fifth pair as large as third pair, each process is triangular and extends
diagonally outward and backward and with an acute tip which sometimes curves slightly forward ; genital segment enlarged a t posterior
corners but without processes ; abdomen considerably narrower and
thinner than genital segment, tapers slightly posteriorly, as long as
genital segment, undivided and with smooth lateral margins ; caudal
rami cylindrical, longer than wide, slightly divergent, with no setae ;
first antenna of four segments, basal segment large and swollen, all four
sparsely armed with small spines; second antenna of two segments,
distal segment in form of a curved claw, divided a t center and with each
half armed with a spine-like seta ; upper lip subtriangular ; mandible
cylindrical, unsegmented, extremely small ; first maxilla as elliptical
mamma, armed with two short spine-like setae; second maxilla of
stout basal portion and a two-segmented portion with terminal segment
curved and fringed with hairs ; maxilliped lacking in female ; each of
four pairs of uniramous swimming legs reduced to simple pointed
knob; ovisacs elongate conical, 7 mm long; eggs minute, about 200
in each sac.
Adult male (Fig. 191) considerably smaller than female, total length
4 mm, greatest width 0.55 mm ; with thoracic segments more or less
separated by grooves ; thoracic processes more reduced than in female
but more prominent than those of M . intestinalis except for first pair
which is wanting in M . orieatalis ; legs larger than in female but still
as uniramous pointed knobs; abdomen unsegmented ; caudal rami
enlarged and nearly parallel ; mouth parts similar to those of female
but with additional pair of stout maxillipeds behind second maxillae.
Life cycle. The life cycle of M . orientalis is not known although it
is most probably of the same pattern as that of M . intestinalis.
Ecology.* I n their paper in which was reported the occurrence of this
copepod in Mytilus californianus, Chew et al. (1963) also reported that
although the average number of copepods per mussel is not significantly
different in Ostrea lurida (2*4), Mytilus edulis (2-3), and M . californianus
(2.5), those in Ostrea lurida are larger, averaging 6-3 mm in length,
than those in the two species of mussels, with those in mussels ranging
from 3-0 to 4.0 mm. Examination of these copepods has revealed that
the smaller specimens (3.0-4.0 mm) are males while the larger ones
(6.0 mm and longer) are females. Although their samples included only
fifty-two 0. lurida (9.6% infected), twenty-four M . edulis (5893%
infected) and twenty M . californianus (65 yo infected), their finding of
proportionally more males in 0. lurida may be significant.
* See note 011 p. 390.