Chapter 8 



Laboratory Experiments on Uptake 



87 



12 16 20 



DAYS OF EXPOSURE 



Figure 9. Accumulation of Cs"^ by Croakers Kept in 

 Sea Water Containing 5 X 10"* Microcuries/Ml. 



The relative concentration of cesium by the 

 various organs is roughly the same for croakers, 

 tuna, or bluefish. The same rank order among 

 the organs is maintained both from ingestion, 

 and from direct uptake. 



Menhaden, a filter feeder, were put into sea 

 water with ruthenium^o** that had been co-pre- 

 cipitated with calcium carbonate. Although a 

 considerable amount of particle settling oc- 

 curred, the menhaden took up the ruthenium in 

 the digestive tract, but the tissues of the fish did 

 not become radioactive to an appreciable extent. 

 Similar experiments using menhaden fed with 

 Ruio6 labelled Arbacia plutei, or Ru^o" labelled 

 Nannochloris cells, gave parallel results. In the 

 latter experiment the fish were allowed to eat 

 the labelled cells for four hours, and then they 

 were put in running sea water. At the time of 

 transfer about 92 per cent of the ingested dose 

 was found in the digestive tract. The gills had 

 0.64 per cent of the dose, and the remainder of 

 the fish, including the skin, had 0.76 per cent. 

 At 128 hours, only 0.05 per cent of the ingested 

 dose remained in the digestive tract. There was 

 0.25 per cent in the fish body or on the skin 

 surface, and 0.01 per cent in or on the gills. 

 At no time was there an appreciable increase in 

 the radioactivity of the body of the fish. 



