Somerton and Donaldson: Parasitism of Lithodes aequispinus by two species of Careproctus 
881 
ability to choose host crabs that are early in their 
molt cycle or that have embryonic and larval resi- 
dence times that are short in relation to the intermolt 
period of the crab. Evidence that snailfish have both 
attributes is provided by the association that we 
found between the embryonic developmental stages 
of crabs and those of the snailfish found wdthin the 
crabs. 
Preference for newly molted crabs is indicated by 
the observed presence of young (uneved) snailfish 
embryos in female golden king crab carrying uneyed 
embryos but not in those carrying eyed embryos or 
remnants of hatched larvae (Table 4), because king 
crabs deposit their eggs soon after molting. Snailfish 
may locate newly molted crabs olfactorally, by de- 
tecting minute traces of molting hormones in the 
same way that some male crabs locate premolt fe- 
males (Ryan, 1966). 
A relatively short embryonic and larval residence 
time, compared with the intermolt period of the crab, 
is indicated by the presence of late snailfish devel- 
opmental stages (eyed embryos and larvae) in newly 
molted (uneyed) female golden king crab (Table 4). 
The length of the embryonic periods for pink and red 
snailfish are unknown, but the large size of the eggs 
and low temperatures of the water in which they in- 
cubate (average bottom temperature on the 1982 
survey was 3.8°C) indicate that the embryonic peri- 
ods are probably quite long. Incubation times are 
Table 4 
Number of female golden king crab observed categorized 
by the development stage of their own embryos and the 
snailfish embryos within their branchial chambers. 
Snailfish stages 
Crab stages 
Uneyed 
Eyed 
Larvae 
Uneyed 
9 
4 
1 
Eyed 
0 
1 
0 
Hatched 
0 
0 
3 
greater in colder water and for fish with larger eggs 
(Pauley and Pullin, 1988), but there are no studies 
applicable to a large egg-producing deep slope spe- 
cies such as Careproctus. If chinook salmon {Onco- 
rhynchus tshawytscha) are used as an approximate 
model for a relatively large egg, cold water species, 
then 4.5 months would be required for hatching at 
3.8°C. (Alderdice and Velsen, 1978). Although this 
rate of embryonic development may be long for a fish, 
it is considerably shorter than that of golden king 
crab which perhaps exceeds 1 year (Somerton and 
Otto, 1986). 
If snailfish can preferentially choose newly molted 
crabs as hosts, then their spawning season must oc- 
cur at the same time as the molting season of the 
