UPTAKE, ASSIMILATION, AND LOSS OF DDT RESIDUES BY 

 Euphausia pacifica, A EUPHAUSIID SHRIMP 



ABSTRACT 



James L. Cox' 



Euphausia pacifica Hensen, an abundant euphausiid shrimp from the California Current, can acquire 

 sufficient DDT residue from its food to account for amounts found in its tissues. Assimilation effii- 

 ciencies for DDT in ingested food are similar to published figures for assimilation of carbon from 

 food. The concentration vs. size function suggested by gas-liquid chromatographic analyses of DDT 

 residues in E. pacifica, however, was quite different from the function predicted by a theoretical food 

 assimilation model. Direct uptake of '"iC-DDT from water was rapid and partially reversible by re- 

 turning animals to unlabelled flowing seawater. Uptake equilibrium was reached within 72 hr for smaller 

 animals (<3 mg dry weight) ; larger animals apparently equiliberated after a longer period. '■'C-DDT 

 present in animals after 2 weeks exposure to unlabelled flowing water was retained in higher amounts 

 in larger animals (>3 mg dry weight). The possible effects of dietary changes, moulting, and surface 

 to volume ratios on observed natural levels are discussed. 



DDT and its congeners are manmade substances 

 which have achieved global distribution. This 

 fact has produced w^idespread concern over their 

 long-term impact in ecosystems and has stim- 

 ulated efforts to study DDT transport from a 

 systems analysis viewpoint (Harrison et al., 

 1970). Indirect evidence (Cox, 1970) suggests 

 an accretion of DDT residues in oceanic food 

 chains and underscores the need to produce in- 

 formation about mechanisms and rates of DDT 

 acquisition and loss by plankton organisms. 

 This paper reports the results of an experimental 

 study of the euphausiid crustacean Euphausia 

 pacifica dealing with quantitative aspects of 

 DDT acquisition from food and water, rates of 

 loss of acquisition from food and water, rates 

 of loss of acquired DDT, and factors affecting 

 equilibration with the surrounding water. 



Euphausiid crustaceans are among the most 

 abundant zooplankters in many oceanic regions. 

 They are the food of commercially important 

 fishes and in general represent an important link 

 of oceanic food chains. E. pacifica is the most 

 abundant euphausiid of the California Current. 

 Ponomareva (1954, 1955, 1959, 1963) has sum- 



' Department of Biology, Southeastern Massachusetts 

 University, North Dartmouth, Mass. 02747. 



marized behavioral and population data on this 

 species, and Lasker (1966) has made extensive 

 laboratory studies of its feeding, growth, res- 

 piration, and carbon utilization. 



METHODS AND MATERIALS 



Laboratory maintenance of E. pacifica has 

 been described by Lasker and Theilacker ( 1965) . 

 Animals were maintained in a 40-liter capacity 

 tub with flowing seawater at 10 to 12° C and 

 fed daily rations of freshly hatched Artemia 

 nauplii. Individuals were kept long enough dur- 

 ing the course of the experimental work for 

 noticeable growth. Mortality was extremely 

 low after the first day that the animals were 

 kept in the tub. 



In direct uptake experiments, '^C-DDT was 

 added in small carrier volumes of ethanol (ca. 

 100 /xliter) to GFC glass fiber filtered seawater 

 (voluriies from 1 to 10 liter) under constant 

 stirring from a magnetic stirrer. Animals were 

 introduced in groups from a small net or turkey 

 baster. At the completion of an uptake run, 

 animals were removed, rinsed briefly with fresh 

 water, and placed in a desiccator for 6 days at 



Manuscript accepted March 1971. 



FISHERY BULLETIN: VOL. 69, NO. 3, 1971. 



627 



