FISHERY BULLETIN: VOL. 69. NO. 3 



Figure 3 shows the results of 2 weeks of 

 "rinsing" on animals originally exposed to "C- 

 DDT for 2 hr. The lower data points show that 

 a fraction of the "C activity was retained, al- 

 though the size vs. estimated i-iC-DDT concen- 

 tration function was altered considerably by the 

 treatment. Figure 4 shows a loss curve con- 

 structed from a series of log-log plots such as 

 those in Figures 1 and 3. The 10.0 mg animal 

 apparently neared equilibrium at the end of the 

 2-week period, but the 2.0 and 3.0 mg animals 

 were still declining. Presumably, the '^C-ac- 

 tivity loss occurred by diffusion of the parent 

 compound ('■'C-DDT) or metabolites into the 

 flowing seawater medium. Some loss may have 

 occurred through moulting. Unfortunately, the 

 conditions of the experiment did not allow any 

 record of moult production. 



ASSIMILATION FROM FOOD 



Animals were isolated in Carolina dishes and 

 kept at 10° C in the dark in 200 ml of GFC 

 filtered seawater and fed known numbers of 

 freshly hatched Artemia nauplii previously 

 labelled with "C-DDT (2.7 ± 0.02 X 10-'= g 

 "C-DDT nauplius, on the average for groups 

 of 10 to 50) . After 24 hr, animals were removed 

 to new dishes and fed daily rations of unlabelled 

 nauplii to ensui'e flushing of the undigested re- 

 mains of the labelled nauplii from the guts of 

 the experimental animals. After 2 days, the 

 animals were removed, rinsed, dried in a desic- 

 cator, and weighed. Amounts of "C-DDT ac- 

 tivity retained were comjiuted by measuring the 

 activity of the dried animals as described in the 

 section on methods. Amounts of labelled nauplii 

 eaten were calculated by counting the numbers 

 left in the dishes after the 24-hr feeding ])eriod. 

 Table 2 summarizes the results of the experiment. 



100- 



< 



O 



o 



>- 

 o 

 a 

 I 

 o 



1.0 



DRY WEIGHT (mg) 



Figure 3. — Loss of "C-DDT from Etiphausia pacifica 

 kept in a flowing water system. Values for the different 

 dry weights were obtained as indicated in the methods 

 section of the text. The solid dots indicate "C-DDT 

 concentrations after 2 weeks of exposure to unlabelled 

 flowing seawater. The open dots are for animals ex- 

 posed to "C-DDT for 2 hr, then "rinsed" in the flowing 

 seawater system for 2 hr before sampling. 



Animal 5 may have had a higher assimilation 

 efliciency because of delayed excretion of the gut 

 contents, presumably attributable to the post- 

 moult condition, i.e., passivity and lack of feed- 

 ing or swimming movements (Paranjape, 1967). 

 Consequently animal 5 was excluded from fur- 

 ther calculations. Animal 1 may have had a 

 lower assimilation efliciency because some loss 

 of labelled material with the moult. The avei'age 

 "C-DDT assimilation efliciencies for animals 

 2 to 4 is only slightly lower than Lasker's (1966) 

 estimates of carbon incorporation efficiency for 

 E. pacifica. 



Table 2. — •■'C-DDT assimilation from labelled Arteinia nauplii by Eiiphausia pacifica. 



Nauplii eoten 



nauplii offered 



(lobelled) 



Percent 

 consumplion 



Ami. "C-DDT 



ingested 



picogroms 



is X IO->2) 



Amf. "C-DDT 

 assimilated 

 picograms 

 (S X 10-U) 



Percent 



assimilation 



efficiency 



34 

 58 

 78 

 80 

 93 



1 Premoult means moult was recovered after feeding on labelled nauplii. Postmoult means moult was recovered after feeding on unlabelled nauplii 



630 



