Chapter 7 



Ecology of Uptake by Aquatic Organisms 



75 



1931). Unfortunately, no experiments on such 

 ionic regulation have been performed with ra- 

 dionuchdes. 



f. Reproductive processes 



The reproductive processes of plants and ani- 

 mals range from simple fission among the 

 unicellular organisms to the very complex rela- 

 tionships among the gametogenic forms. Dur- 

 ing reproduction there is a transfer of materials 

 from the parent to the offspring. 



In simple fission, the parent cell splits in 

 two and each offspring receives approximately 

 half of the parent material and thus only half 

 of any radiomaterial that may have been pres- 

 ent. Under conditions of chronic exposure, the 

 offspring of organisms that reproduce by fission 

 will incorporate usable radiomaterials into their 

 bodies and a state of equilibrium eventually 

 will be reached. 



Among the egg-laying forms, most of the 

 material received by the offspring is derived 

 from the contents of the egg. In this form of 

 reproduction, once the egg is laid there will be 

 no further loss of radiomaterials from the 

 mother or gain to the offspring. This applies 

 even when the environment is contaminated 

 and there is chronic exposure of the parents, 

 because the protective coverings of the egg pre- 

 vent the entrance of radiomaterials. 



Among the forms that bear their young alive, 

 however, there is usually some continuous trans- 

 port of materials between the mother and the 

 embryo. In such an instance it is probable that 

 the embryo will accumulate radiomaterials with 

 a resultant loss to the mother. If chronic ex- 

 posure of a mother carrying an embryo con- 

 tinues during pregnancy, a state of equilibrium 

 may eventually be reached between the mother 

 and the environment and between the mother 

 and the embryo. 



During embryological development of all 

 kinds there is a "biological dilution" of radio- 

 materials through cell division and growth. This 

 statement applies primarily if there has been 

 an acute exposure to radiomaterials or if the ex- 

 posure has stopped with the commencement of 

 the embryological development. 



g. Molting 



In instances where the embryos pass through 

 a series of metamorphic stages, there is a loss of 

 radiomaterials from stage to stage as, for ex- 

 ample, the loss from instar to instar in insects 

 through molting. Furthermore, it has been 



demonstrated by Chipman and coworkers (per- 

 sonal communication) that there is an increased 

 accumulation of elemental constituents in crus- 

 taceans prior to molting, and a loss of such ma- 

 terials when the carapace is lost. 



h. Age and groivth 



It has been established (Olson and Foster, 

 1952) that younger, more rapidly growing 

 fishes accumulate relatively greater amounts of 

 radiomaterials than do older, more slowly grow- 

 ing individuals. This phenomenon is probably 

 a reflection of the more rapid metabolism that 

 accompanies the growth of the younger fishes. 

 It is not known whether the accumulation of 

 radiomaterials by other aquatic vertebrates and 

 invertebrates is a function of age and growth. 



i. Effect of temperature on cold-blooded and 

 luarm-blooded animals 



In general, the body temperatures of warm- 

 blooded animals are more or less constant 

 whereas the body temperatures of cold-blooded 

 animals largely depend upon the temperature of 

 the environment. Similarly, the rate of metab- 

 olism in warm-blooded animals is generally in- 

 dependent of temperature changes in the en- 

 vironment while that in the cold-blooded 

 animals is largely dependent upon external 

 temperatures. Changes in temperature affect 

 the rates of chemical reactions and hence chemi- 

 cal processes that involve the accumulation of 

 elements in the body tissues are temperature 

 dependent. 



Generally speaking, all cold-blooded aquatic 

 organisms exhibit seasonal changes in the up- 

 take and accumulation of radiomaterials from 

 the environment. Davis, et al. (1953), and 

 Krumholz (1954, 1956) have shown that there 

 is a direct correlation between an increase in 

 temperature and an increase in the accumulation 

 of radiomaterials in fishes of the Columbia 

 River, Washington, and of White Oak Lake, 

 Tennessee, respectively. This increase in accumu- 

 lation is apparently a reflection of the increase 

 in the speed of the metabolic processes with 

 rising water temperatures. However, Krumholz 

 (1956) suggested that the fishes in White Oak 

 Lake entered a period of dormancy following 

 August 1 and lost about two-thirds of their ac- 

 cumulated radioactivity during the subsequent 

 two months even though the water tempera- 

 tures were much the same as they were during 

 the earlier part of the summer. 



In studies of the uptake of strontium 89 by 



