308
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
11. Myicola metisiensis Wright, 1885. (Figs. 205 and 206)
(Order Cyclopoida; family Myicolidae)
Myicola metisiensis, the genotype, was originally found and described by Wright (1885) between the gill lamellae of Mya arenaria
collected a t the village of Little Metis, Quebec, on the Gulf of St.
Lawrence. It was redescribed by Wilson (1932) from the mantle cavity
of the same host collected a t Wellfleet, Massachusetts, and placed in
the family Lichomolgidae. Wright had placed this species in the no
longer recognized family Corycaeidae. However, in following Pearse
(1947), I am placing it in the cyclopoid family Myicolidae.
Adult female (Fig. 205) averaging 3 mm long, first
four thoracic segments subequal, broader than long ; fifth segment
smaller than first abdominal segment ; double genital segments nearly
as long as remaining three abdominal segments; furcal segments as long as
last two abdominal segments, with six setae of which three are
apical and one subapical ; rostrum shield-shaped ; anterior antennae
as long as head, with first, second, and fifth segments being the longest ;
second antennae directed downwards, shorter than first pair ; labrum
with lateral borders denticulated and posterior border emarginated ;
mandible with two setose lobes and two setose filaments; maxillae
with three setae of which the middle is the longest; two basal joints
of first maxillipeds tumid, with two converging oblique patches of
spines, distal joint of first maxilliped with strong seta and terminating
in two curved setose filaments of which the more slender is attached
like a palp ; first through fourth legs biramous ; basipodite of first leg
with a row of strong spines on ventral surface which decrease in rigidity
on the second and third legs and are absent from the fourth ; fifth leg
uniramous, of three podomeres, two basal ones each with a seta while
the distal podomere has two apical setae and a group of subequal spines ;
egg sacs cylindrical, 1.0 mm x 0.5 mm.
Adult male (Fig. 206) very similar to female, smaller, measuring
1-75 mm or less in length ; thoracic segments gradually decreasing in
breadth anteroposteriorly ; posterior borders of genital and two
subsequent abdominal segments denticulated ; second maxilliped with
basal joint denticulated ; spermatophores subpyriform, 0.2 mm x
0.1 mm.
Life cycle. The stages in the life cycle of this species are not known.
Relative to the mode of infection of the soft clam, Wright (1885) has
stated :
I have found some in the suprabranchial chambers, which would seem to
indicate entry through the cloaca1 siphon, while I have found others, head
Description.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
11. Myicola metisiensis Wright, 1885. (Figs. 205 and 206)
(Order Cyclopoida; family Myicolidae)
Myicola metisiensis, the genotype, was originally found and described by Wright (1885) between the gill lamellae of Mya arenaria
collected a t the village of Little Metis, Quebec, on the Gulf of St.
Lawrence. It was redescribed by Wilson (1932) from the mantle cavity
of the same host collected a t Wellfleet, Massachusetts, and placed in
the family Lichomolgidae. Wright had placed this species in the no
longer recognized family Corycaeidae. However, in following Pearse
(1947), I am placing it in the cyclopoid family Myicolidae.
Adult female (Fig. 205) averaging 3 mm long, first
four thoracic segments subequal, broader than long ; fifth segment
smaller than first abdominal segment ; double genital segments nearly
as long as remaining three abdominal segments; furcal segments as long as
last two abdominal segments, with six setae of which three are
apical and one subapical ; rostrum shield-shaped ; anterior antennae
as long as head, with first, second, and fifth segments being the longest ;
second antennae directed downwards, shorter than first pair ; labrum
with lateral borders denticulated and posterior border emarginated ;
mandible with two setose lobes and two setose filaments; maxillae
with three setae of which the middle is the longest; two basal joints
of first maxillipeds tumid, with two converging oblique patches of
spines, distal joint of first maxilliped with strong seta and terminating
in two curved setose filaments of which the more slender is attached
like a palp ; first through fourth legs biramous ; basipodite of first leg
with a row of strong spines on ventral surface which decrease in rigidity
on the second and third legs and are absent from the fourth ; fifth leg
uniramous, of three podomeres, two basal ones each with a seta while
the distal podomere has two apical setae and a group of subequal spines ;
egg sacs cylindrical, 1.0 mm x 0.5 mm.
Adult male (Fig. 206) very similar to female, smaller, measuring
1-75 mm or less in length ; thoracic segments gradually decreasing in
breadth anteroposteriorly ; posterior borders of genital and two
subsequent abdominal segments denticulated ; second maxilliped with
basal joint denticulated ; spermatophores subpyriform, 0.2 mm x
0.1 mm.
Life cycle. The stages in the life cycle of this species are not known.
Relative to the mode of infection of the soft clam, Wright (1885) has
stated :
I have found some in the suprabranchial chambers, which would seem to
indicate entry through the cloaca1 siphon, while I have found others, head
Description.