100 



Atomic Radiation and Oceanography and Fisheries 



move into an affected area or, if not picked up 

 at once following death, they decay so rapidly 

 in the warm tropical waters as to be undetecta- 

 ble in a few hours, thus escaping notice. 



II. Somatogenic Effects of Ionizing Radiation 



If we consider genetic effects in the strict 

 sense of damage to chromosomes or genes, to 

 the extent the modified characteristics are passed 

 from one generation to the next, there is little 

 to be found in the published literature describ- 

 ing work on marine or fresh-water forms. Some 

 effects on aquatic forms have been described, 

 however, where gametes were exposed to radia- 

 tion prior to zygote formation. The effects in 

 such cases are due, at least in part, to somatic 



which died during the incubation period con- 

 tained conspicuously abnormal embryos. The 

 abnormalities could be attributed to deficiencies, 

 improper differentiation of cell masses, dispro- 

 portionate growth, or combinations of these fac- 

 tors. Abnormal types of embryos occurred 

 among the progeny of control parents and of 

 parents which had received low doses of radia- 

 tion which were almost identical with the types 

 which occurred among the progeny of parents 

 receiving large amounts of radiation. However, 

 as the amount of radiation increased the relative 

 abundance of malformed embryos increased and 

 the degree of development attained decreased. 

 Practically all of the embryos from parents 

 treated with 1500 r and 2500 r were so ab- 



TABLE 6 Effect on Trout Eggs from Irradiating the Parent Fish ^ 



(Values are per cent of eggs which died at each stage) 



Number of r units received by parents 



Stage of ,, A _ , 



Development 50 100 500 750 1000 1500 2500 



No embryo 18.5 32.2 23.0 24.4 42.6 41.5 68.1 83.6 



Blastoderm 0.8 0.3 3.2 5.9 0.6 3.2 2.9 4.5 



Embryonic axis 4.3 4.6 4.3 8.2 21.1 29.5 22.1 11.5 



Blastopore closed 1.0 4.4 3.7 23.6 22.5 15.5 5.5 0.3 



Eyed 6.3 9.1 16.2 8.6 3.5 2.1 0.3 0.1 



Hatching 8.7 11.4 10.1 14.5 6.3 6.3 0.9 



Total 39.6 62.0 60.5 85.2 96.6 98.1 99-8 100 



1 Data from means (unpublished) of figure 1 from Foster et al. (1949). 



damage but will be considered here because they normal that they died before closure of the 



represent some changes which may occur in oflF- blastopore. Irradiation of the parent fish thus 



spring of irradiated parents. increased the frequency of occurrence of malfor- 



The classical work of Henshaw and his col- mations." 



leagues with the eggs and sperm of the sea Table 6 illustrates that egg mortality was di- 



urchin Arbacia demonstrated that X-radiation rectly related to the dose received by the parent 



of the gametes delayed the first cleavage. Ef- fish and that the degree of development ob- 



fects of X-rays on gametes of fish have received tained by the embryo decreased at the higher 



some attention. In spite of massive doses of exposure levels. 



X-rays — 100,000 to 200,000 r — (Rugh and Irradiation of gametes prior to "fertilization" 



Clugston, 1955) to the eggs and sperm of is, of course, not the only means of producing 



Fundulus heterocUtus, fertihzation can take abnormal embryos with ionizing radiation. We- 



place and some embryonic development is pos- lander (1954) found that abnormalities in- 



sible although this may be parthenogenic from creased with dose among trout embryos irradi- 



irradiated sperm. Solberg's (1936) work with ated at the 32-cell and early eyed stages. The 



Oryzias indicates that spermatozoa are three to production of phenocopies has been tentatively 



four times as sensitive to radiation as ova, how- established. Welander, as stated earlier, found 



ever. Foster (1949) found that that trout irradiated with 200 and 400 r at the 



"The mean mortalities of the eggs obtained 32-cell stage had abnormal dorsal and adipose 



from parents subjected to 500 or more roentgen fins. Such anomalies arising from irradiation of 



units were significantly greater than that of the cleavage stages would appear to result from a 



eggs from the control parents. Most of the eggs disturbance of the precursors. 



