212 



JACKSON, VESSEY. AND BASTIAN 



Boken 6184 



Lujor /.329 



Aomon 1981 

 /2257^ 



Enewetak 2.6 



Fig. 6 The sections in the circles represent the percentage of abnormal antemolar palatal ridge pat- 

 tern in the Polynesian rat populations. The four islets with the highest percentages are centered 

 between islets with highest contamination data. These values given for several of the larger islets are 

 average fallout contamination levels in R/hr. corrected to H + 1 hr past detonation of the atomic 

 testing devices (Temme, 1981). 



three in Hawaii. They suggested that the greater variation 

 in the Enewetak rats might be due to the nuclear detona- 

 tions. 



In 1980 blood samples were taken from roof rats on 

 Medren (N=16), Enjebi (N=17), Runit (N = 35) for 

 analysis of protein variation. Of 29 loci checked by electro- 

 phoresis, 13 were polymorphic. 



Heterozygosity (the percent of all loci per individual 

 that were heterozygous) was lowest on Medren (16.4), 

 intermediate on Enjebi (19.7), and highest on Runit (21.1). 

 The percentage of loci that were polymorphic also 

 increased in the same order, from 38% to 41% to 45%. 

 These findings raise the possibility that increased radiation 

 also may have increased selection for heterozygotes or 

 may have increased mutation rates on Enjebi and Runit. 



Nei's (1972) genetic distance among the three islands 

 varies from 0.95 to 0.96. Comparable data for isolated 

 house mouse populations showed higher values, from 0.98 

 to 0.99 (Nei, 1972), suggesting greater isolation among 

 the rats at Enewetak. 



SUMMARY 



Roof rats and Polynesian rats, introduced to the atoll 

 by 20' century commerce and the Micronesians, respec- 

 tively, were present allopatrically on the larger islets. Of 

 necessity, they were largely vegetarians. Reproductive 

 cycles were keyed to rainfall patterns. High density popula- 

 tions had high stress indices, including high parasite loads. 



The rats, at the top of the terrestrial food pyramid, 

 constituted a bioenvironmental monitor that was rarely uti- 

 lized during the several test programs. Bioconcentration of 

 radioisotopes, especially Cs and Co, occurred; rats 

 implanted with dosimeters were determined to function as 

 environmental radiation monitors. We hypothesized that 

 roof rats on Enjebi survived the nearby nuclear detonation. 



Analysis of plasma transferrins indicated greater hetero- 

 zygosity in the northern atoll rat populations. The 

 incidence of oral palatal ridge deformations also was posi- 

 tively correlated with environmental radiation levels, but 

 other gross indications of radiation effect were not found. 



