Results and DiscussionBioconcentration of waterborne Cd by oval squidDuring the exposure and elimination periods, themean and standard deviation of the water temperature,dissolved oxygen concentration, pH and salinity were19:8  0:9°C, 6:4  1:0 mg=l, 7.9 and 34:5  0:9, re-spectively. The mean Cd concentration in the seawatersamples was 0:204  0:017 mg=l during the exposureperiod. Cd was not detected (< 0:01 mg/l) in the waterof the control, or in the water of the elimination ex-periment. The mean body weight and mean mantlelength of the squid at sampling were 35:7  19:5 g and7:9  1:8 cm, respectively.Whole-body Cd concentrations continued to riseduring the exposure period (Fig. 2). While Cd was notdetected (<0:1 lg/g ww) in three control squid, themean whole-body Cd concentration in the squid ex-posed to Cd was 3:10  0:18 lg/g ww after 14 days ofexposure. Therefore, their mean Cd bioconcentrationfactor (BCF) after 14 days of exposure ± calculated bydividing the mean whole-body Cd concentration(3.1 lg/g ww) by the seawater Cd concentration(0.2 mg/l) ± was 15.5. This BCF value is less than thoserecorded for other aquatic organisms, ranging from 22 forgrass shrimp to 710 for blue mussel (US EnvironmentalProtection Agency, 1984). The mean whole-body Cdconcentration continued to decrease during the elimina-tion period; after 14 days it was 1:90  0:05 lg/g ww.During the exposure period, Cd concentrations ineach organ continued to rise (Fig. 3). In particular, Cdconcentrations in the liver and gill increased immedi-ately after exposure to Cd. In contrast, the mean Cdconcentrations in the mantle, ink sac and others groupwere relatively low, and changed little during the expo-sure and elimination periods. The mean Cd concentra-tions in the liver, gill, digestive tract, mantle, ink sac andothers group on the fourteenth day of the exposureperiod were 49.3, 19.2, 7.08, 0.79, 1.35 and 1.62 lg/gww, respectively. Although Cd concentrations in the gilland mantle decreased immediately after the eliminationperiod began, the mean Cd concentration in the liver onthe fourth day of the elimination period was higher thanthat found on the fourteenth day of the exposure period.In the squids, Ommastrephes bartrami (Castillo andMaita, 1991) and Todarodes paci®cus (Tanaka et al.,1983; Dohi et al., 1986), Cd binds to a Cd-bindingprotein; in oval squid, Cd may be ®nally distributed tothe liver and persist there because of binding to a similarprotein. Although the proportions of Cd accumulated ineach organ in relation to that accumulated in the wholebody showed no trends over time, the liver held thehighest proportions ± about 50% during the exposureand elimination periods (Fig. 4). The mean proportionsof the whole-body Cd content of the liver, gill, digestivetract, mantle, ink sac and others were 46.4%, 21.6%,5.8%, 15.4%, 0.76% and 15.4% during the exposure
period, and 52.5%, 12.6%, 8.4%, 9.7%, 0.68% and
16.2% during the elimination period, respectively. The
liver of the cuttle®sh, S. ocinalis and octopus, Eledone
cirrhosa, caught on the French coast, also exhibits the
highest Cd concentration and proportion among the
organs (Miramand & Bently, 1992). Protein-bound Cd
accumulates in the liver of the squid, T. paci®cus
(Tanaka et al., 1983; Dohi et al., 1986). In the oval
squid, the Cd in the liver was certainly protein-bound;
consequently the liver had the highest concentration and
body proportion of Cd in the present study. This is true
in other cephalopods (Martin and Flegal, 1975; Smith
et al., 1984; Finger and Smith, 1987; Miramand and
Bently, 1992; Kurihara et al., 1993).
The whole-body Cd concentrations were measured in
17 ®shes that had been in the tank with the oval squid
but had not been preyed upon by them. Cd could not
detected in seven ®shes (<0:1 lg/g ww), but in the re-
mainder the mean Cd concentration was 0:32  0:11 lg/
g ww or 0:16  0:10 lg/®sh. Having detected the Cd
concentration in ®sh that had not been preyed upon, the
proportion of Cd in oval squid that had been absorbed
from the food could be then calculated. The daily food
consumption rate of the oval squid (mean body weight
 36 g), was calculated from the weight of the ®sh
preyed upon as 10:5  1:1% of the squidÕs body weight.
These rates were similar to the rate found by Segawa
(1990), which was experimentally determined. Assuming
that all Cd in the food was absorbed by the squid, their
mean Cd intake from food over the 14-days exposure
period was could be estimated at 0.45 lg/g ww
0:105  0:32  14. The mean Cd residue in the squid
after 14 days of exposure was 3.1 lg/g ww; therefore the
proportion of Cd absorbed from the food was about
15%, the remainder coming from the water. These re-
sults and estimations suggest that most of the Cd ac-
cumulated by the oval squid was absorbed from the
water, although the BCF for bioaccumulation of Cd by
oval squid was lower than those recorded for other
marine organisms.
Biomagni®cation of Cd from ®sh larvae by oval squid
During the exposure and elimination periods, the
mean water temperature, dissolved oxygen, pH and sa-
linity were 22:3  1:3°C, 6:4  1:0 mg=l; 8:0  0:1 and
34:5  0:9, respectively. The mean Cd concentration in
the water was 0:122  0:021 mg=l during the exposure
period, while Cd was not detected (<0:01 mg/l) in the
water of the control, or in the water of the elimination
experiment. The mean body weight and mean mantle
length of the squid were 7:4  2:5 g and 5:0  1:7 cm,
respectively. The mean Cd concentrations in the mum-
michog used as prey for the squid were 0.73, 0.86 and
1.31 lg/g w.w. after 4, 10 and 15 days of exposure, re-
spectively. After 8 days of elimination, the mean Cd
concentration in the mummichog was 0.50 lg/g ww.
While Cd was not detected (<0:1 lg/g ww) in two
control squid, the mean whole-body Cd concentration in
the squid exposed to Cd in food and water was
4:18  0:69 lg/g ww after 15 days of exposure (Fig. 5).
The BCF of waterborne Cd by the squid was 15.5 after
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