Whirling disease (Myxosoma cerebralis): control with ultraviolet irradiation and effect on fish

Water contaminated by Myxosoma cerebralis was disinfected with ultraviolet irradiation to control whirling disease. Irradiation at 18,000 microwatt seconds/cm2 (MWS/cm2) reduced infectivity of M. cerebralis by 31-86% and 27,650 MWS/cm2 reduced infectivity by 86-100%, even in the presence of a small amount of silt.

Population genetics of Lebistes (Poecilia) reticulatus Peters (Poeciliidae; Pisces). I. Effects of radiation-induced mutations on the segregation ratio in postirradiation F 2

Wild-type germ cells of the viviparous fish, Lebistes (Poecilia) reticulatus, were irradiated in the stages of oogonia, spermatogonia or spermatozoa with 1000 R of X rays at a dose-rate of 200-220 R/min. The grown-up fish were mated after irradiation or sham treatment to unirradiated mutant fish homozygous for three recessive gene loci, causing albinism, lack of yellow and reddish pigmentation ("blue" constitution), and diminution of the size of melanophores ("blond" constitution). As compared to the control series, the phenotypic segregation ratios in the adult F(2) generation after irradiation was changed significantly in favour of wild-type and blue fish, whereas the proportion of albinotic, blond and "white" (= blond + blue) guppies was lowered. This unidirectional effect in postirradiation F(2) was greatest after exposure of spermatozoa with 2 x 500 R (24 hr apart), followed by single doses of 1000 R to spermatogonia and oogonia. These results were explained in terms of a synergistic interaction of recessive radiation-induced mutations in the heterozygous state with those genotypes of the guppy which affect the formation of melanophoric patterns and the synthesis of melanins.

Growth rate measurements in gamma irradiated catfish

The effect of whole body gamma irradiation at the low exposure levels of 100, 200 and 400 r has been studied on the rate of growth of both juvenile and adult males and females of Clarias lazera. Irradiation causes, in general, significant retardation in rate of increase in length of growing fish. Such retardation is especially marked in adult females. Irradiation causes also diminution in the percentage increase in weight of adults especially the females. In juvenile fish, radiation exposure at the levels of 100 and 200 r accelerates the rate of increase in weight while the higher exposure level of 400 r results in a significant retardation. The exposure level of 100 r increases the ratio weight/length only in juveniles. Exposure levels of 200 and 400 r decrease such a ratio.

The results obtained are explained in correlation with the general knowledge of biological radiation syndrome and discussed in view of the relevant literature.

The biological effects of radioactive waste

The discharge of radioactive waste into the marine environment is, in general, limited by the requirement that the resulting increments of dose to members of the general public are within internationally agreed limits. The implicit assumption is made that when this require­ment is met the fauna and flora of the marine ecosystem, which are generally less radiosensitive than man, are not at risk. The data relating to the effects of both acute and chronic irradiation on marine species are reviewed and the dose rates which can occur in contaminated environments due to the recon­centration of activity, either by the animals themselves or by some component of their habitat, e. g. silt, are indicated. From this it is possible to predict that present waste disposal practices are unlikely to have any observable effect in the natural environment. Nevertheless, further research is necessary to find more sensitive indicators of damage at both the individual and population levels.

Quantitative changes in breeding groups of Lebistes after irradiation

Neonatal guppies of a wild-coloured inbred strain were X-irradiated with 1000 R, corresponding to early oogonia and spermatogonia. At sexual maturity the irradiated fish and their sham-treated controls were mated to unirradiated guppies of another stock. The proportions of the body shape and the number of vertebrae of the F1 and F2 generations were determined. The quantitative characters controlled by polygenes in both experimental and control groups showed that the number of vertebrae increased in the F1 and decreased in the F2. The changes in body proportions reveal a trend towards a more compact type after ancestral irradiation. The variability coefficient was greater among females of the irradiated series. Shifts in the mean values were combined with alterations of viability revealing an increase in postnatal mortality and a reduction of litter size in the backcross generation. An increase in litter size and a decrease in postnatal mortality appeared in the F1 and F2 generations where radiation-induced detrimental mutations were less likely to become homozygous.

Inheritance of radiation-induced spinal curvatures in the guppy Lebistes reticulatus

Hereditary changes in the shape of the vertebral column in Lebistes reticulatus appeared after ancestral irradiation of immature germ cells with 500 or 1000 R of X-rays. Although the mutant to wild-type ratios in the F2 generation after outcrossing fitted a digenic and a trigenic segregation ratio, respectively, the quantitative characters in question are assumed to be caused by recessive mutations of polygenes which are highly mutable.

Radiation-induced spermatogonial exchange between the X and Y chromosomes in the guppy

Irradiation of male germ cells in newborn guppies, Lebistes reticulatus Peters, causes an increase in the exchange frequency between the X and Y chromosomes in comparison to unirradiated controls among the offspring of the irradiated males, provided the offspring are produced during an interval between 161 and 283 days after irradiation. No significant increase of crossing-over frequency was obtained among offspring produced during the interval between 59 and 145 days after irradiation. It is concluded that irradiation of early spermatogonia (59 to 145 days postirradiation) does not increase the exchange frequency between sex chromosomes whereas the irradiation of stem cells (161 to 283 days) provides a significantly higher incidence of crossing-over events in the irradiated series than in the controls. The excess of crossovers in the irradiated stem cells of spermatogenesis is due only to clusters of crossovers in the irradiated series, since on excluding the clusters no difference between irradiated and control series could be found.

Comparative effects of chlortetracycline, freezing, and gamma radiation on microbial population of ocean perch

The microbial populations in chlortetracycline (CTC)-treated (50, 100, 200, and 500 ppm), frozen (-15 C), and irradiated (0.1 Mrad) ocean perch (Sebastodes alutus) were compared. The control sample spoiled at 7 C, primarily because of the growth of Pseudomonas. Irradiation changed this to Achromobacter-dominated spoilage. Freezing or CTC treatment altered the spoilage pattern very little. CTC was particularly effective against ultraviolet fluorescent Pseudomonas species at the higher concentrations. Freezing and CTC were not effective against "coryneforms."

Changes in the microflora of irradiated petrale sole (Eopsetta jordani) fillets stored aerobically at 0.5 C

The microfloral changes on irradiated petrale sole fillets during aerobic (packaged with oxygen-permeable film), refrigerated storage were determined by the identification of bacterial and yeast isolates to the generic level. The samples were irradiated at 0.0, 0.1, 0.15, 0.2, 0.3, and 0.4 Mrad by use of a cobalt-60 gamma source, were stored at 0.5 C, and were examined periodically for spoilage, total microbial population, and composition. The preirradiation flora of the fresh fillets consisted of coryneforms, Achromobacter, Micrococcus, Flavobacterium, Pseudomonas, and Lactobacillus. Immediately after irradiation, Micrococcus, Achromobacter, coryneforms, and Bacillus were predominant. The flora of the nonirradiated fillets at the time of spoilage consisted of Pseudomonas and Achromobacter. The flora of the irradiated fillets at the time of spoilage consisted of Achromobacter and Trichosporon.