Mutational changes of quantitative morphological traits in the convict cichlid (Cichlasoma nigrofasciatum Guenther) after irradiation of parental spermatogonia and oogonia with different doses of X-rays.

10 continuous and 6 discrete variables of body dimensions as well as 16 proportions calculated from them were determined in postirradiation F1 convict cichlid fish (Cichlasoma nigrofasciatum) which were derived from spermatogonia and oogonia both exposed to either 0 (controls), 250, 500, 750, 1000, or 2000 R of X-rays. While no interactions with sex or radiation dose were found, clear dosage effects and some sex effects occurred. The highest response for almost all quantitative traits examined as well as for variants of coloration or of vertebral aberrations appeared after 250 R to both parental germ cells. The lowest effectiveness was observed for almost all characters under investigation after 0 and 500 R. Accordingly, the largest difference between the 6 different treatment groups was found between 250 and 500 R, followed by 250 and 0, 250 and 1000, and 250 and 750 R to parental gonia. The present finding on the alterations of quantitative morphological traits completely corresponds to the changes of intraspecific aggressiveness as found for the same individual fish in a previous study thus confirming the complete congruence of the mutational response of quantitative morphological characters with that of behavioral traits to ionizing radiation.

Social cohesiveness of convict cichlid fish (Cichlasoma nigrofasciatum Guenther) after irradiation of parental spermatogonia and oogonia with different doses of x-rays.

Comparisons of social cohesiveness were made between F1 convict cichlids (Cichlasoma nigrofasciatum) derived from gonial germ cells which were exposed to 0 (controls), 250, 500, 750, 1000, or 2000 R of X-rays. The cohesiveness was determined by counting the distribution of each ten fish of every F1 group among 12 equal squares within a shallow test tank measuring 80 by 60 by 20 cm. While an increase in cohesiveness was detected in F1 males, as compared to the controls after irradiation with 500 R, the cohesiveness of F1 females decreased after 750 and 2000 R. The increase in male cohesiveness may be associated with a reduction of intermale aggressiveness as found in previous studies.

Change in the radiation responses of oogonia in the embryos and fry of the fish Oryzias latipes.

Embryos of the fish Oryzias latipes were irradiated with 1000 R of X-rays 1 day before hatching,and the post-irradiation change in the female germ-cell population was observed. Scarcely any reduction in the number of oogonia was observed, but their proliferation was inhibited. Repopulation occurred between 12 and 20 days after hatching. These responses were quite different from those of germ cells in the irradiated fry (Hamaguchi and Egami 1975). Embryos and/or fry were also exposed to 1000 R of X-rays 1 day before hatching and 0, 1, 2, and 3 days after hatching. A comparison of their responses suggested that the change in the radiation responses of oogonia is correlated with the initiation of meiosis.

Biological responses of Habrobracon to spaceflight.

Since the interaction of the parasitic wasp Habrobracon with the space environment could not be prejudged, we decided to test approximately 30 different parameters of a genetic, mutational, biochemical, behavioral, and physiological character in the one spaceflight we had at our disposal. These parameters were examined at six different exposures of gamma-radiation (including 0 dose) in flight, resulting in about 180 different endpoints in all. The most profound effects of spaceflight in conjunction with radiation were decreased hatchability and enhanced fecundity of eggs exposed to spaceflight at different stages of oogenesis. The interpretation we favor is that these two endpoints are reflections of chromosomal non-disjunction in the former case and inhibition of cell division in the latter. Our most comprehensive study of mutagenesis was on sperm, where dominant lethality, recessive lethality, translocations, and visible mutations were assayed; the only effect found was a threefold enhancement of the recessive lethal mutation frequency in the non-irradiated sperm in the orbited Habrobracon males. Behavioral and biochemical differences were found. Mating activity of orbited males was severely disrupted and xanthine dehydrogenase activity was sharply decreased in the irradiated flight animals, an unexpected observation. Postflight experiments were like the ground-based control experiments in all aspects but one. Under conditions of vibration similar to those encountered during the launch and re-entry, the mutation frequency in the sperm increased by a factor of three over that of the non-vibrated control.