871 
Abstract.-Aiong the continental 
slope of the eastern Bering Sea, two 
species of Careproctus snailfishes de- 
posit eggs within the branchial cham- 
bers of the commercially important 
golden king crab ( Lithodes aequi- 
spinus). The larger of the two species 
is the pink snailfish (C. furcellus ) ; the 
smaller species is an undescribed spe- 
cies referred to as the red snailfish. 
According to 1982 trawl survey data, 
incidence of snailfish eggs and larvae 
within crab branchial chambers in- 
creases with carapace length (CL) and 
is greater for male than female crabs. 
A logistic model fitted to the incidence 
data predicts that a 140-mm-CL male 
will have an incidence of 0.52, approxi- 
mately 1.9 times greater than the inci- 
dence for a 100-mm male. Incidence for 
a 100-mm-CL male is approximately 
1.9 times greater than that for a female 
of equal size. On the basis of develop- 
mental stages of embryos carried by 
female golden king crab and the devel- 
opmental stages of snailfish embryos 
within a female’s branchial chambers, 
snailfish appear to deposit eggs prefer- 
entially in crabs that are early in their 
molt cycle. The presence of the egg 
masses results in gill compression, lo- 
calized necrosis of gill tissue and, in 
extreme cases, total loss of gill tissue 
on one side of the body. For crabs of 
commercial size, the presence of eggs 
and larvae increases mortality within 
the holds of fishing vessels by 35%. The 
current incidence of eggs and larvae in 
commercial sized males, however, is so 
low that the effect on the commercial 
fishery is considered to be small. 
Manuscript accepted 7 January 1998. 
Fish. Bull. 96:871-884 (1998). 
Parasitism of the golden king crab, 
Lithodes aequispinus, by two species 
of snailfish, genus Careproctus 
David A. Somerton 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE, Seattle, Washington 98115 
E-mail address: David.Somerton@noaa.gov 
William Donaldson 
Alaska Department of Fish and Game 
2 1 1 Mission Road 
Kodiak, Alaska 996 1 5 
Liparid snailfish in the genus 
Careproctus extrude eggs through 
an anteriorly positioned ovipositor 
into the branchial chambers of large 
lithodid crabs. This relationship 
was first described, independently, 
by Rass (1950) and Vinogradov 
(1950) for C. sinensis and Para- 
lithodes camtschatica in the north- 
west Pacific. Subsequent studies, 
however, have shown that addi- 
tional species both within Para- 
lithodes as well as within three 
other lithodid genera (Lithodes, 
Lopholithodes and Paralomis ), also 
serve as hosts to various Careproctus 
species and that the association ap- 
pears to be widespread according to 
reports from the North and South 
Pacific and South Atlantic (Hunter, 
1969; Parrish, 1972; Peden and 
Corbett, 1973; Anderson and Cailliet, 
1974; Balbontin et ah, 1979; Melville- 
Smith and Louw, 1987; and Love and 
Shirley, 1993). 
The advantages that snailfish gain 
by placing their eggs within an en- 
closed, constantly aerated space have 
been recognized since the association 
between Careproctus and lithodid 
crabs was discovered (Rass, 1950). 
The disadvantages to the crab, how- 
ever, remain equivocal, with reports 
of no obvious damage (Hunter, 1969; 
Parrish, 1972), minor gill compres- 
sion by the egg mass (Anderson and 
Cailliet, 1974; Melville-Smith and 
Louw 1987), and gill bleeding (Love 
and Shirley, 1993). Knowledge of the 
disadvantages is important because 
most affected lithodid species support 
commercial fisheries. 
In this paper, we report on the 
deposition of egg masses by two spe- 
cies of Careproctus into the bran- 
chial chambers of the golden king 
crab ( Lithodes aequispinus), a large, 
commercially harvested lithodid 
occurring along the continental 
slope of the North Pacific (Somerton 
and Otto, 1986). The identity of the 
two Careproctus species is uncer- 
tain because the taxonomy of the 
family Liparididae is problematic 
and incomplete (Allen and Smith, 
1988). The larger species (Fig. 1), 
henceforth called the pink snailfish, 
is certainly within the C. melanurus 
group of morphologically similar 
species (Allen and Smith, 1988) and 
is likely to be C. furcellus which has 
been observed throughout the 
Bering Sea and Aleutian Islands 
(Kido, 1988). The smaller species 
(Fig. 1), henceforth called the red 
snailfish, is tentatively identified as 
a member of the C. mederi group 
described by Kido (1988), who re- 
