Exposure of organisms to microgravity can induce morphological, physiological, and behavioral modifications which normalize after re-entry in 1g-condition within hours to few weeks. Development of Xenopus laevis tadpoles, their metamorphosis, and adults' growth were monitored for 3 years after their flight on the 12-day Soyuz mission TMA13 to the International Space Station. At onset of microgravity, tadpoles had just developed the hind limb (stage 47) or forelimb bud (stage 50). Recordings during the first 4 days after landing revealed no differences of developmental progresses and growth between flight and ground tadpoles. Further development and growth were strongly retarded in all animals; nevertheless, significant differences appeared between flight and ground groups during this postflight period. They include (1) acceleration of development in stage 47 but not stage 50 flight tadpoles; (2) earlier metamorphosis of stage 47 flight tadpoles compared to their 1g-ground controls while stage 50 flight tadpoles metamorphosed later than their ground controls; (3) maintenance of a tail during the juvenile stage exclusively in some stage 47 flight animals, and (4) accelerated growth of stage 47 male flight toads but retarded growth of stage 50 flight males compared to the respective 1g-ground control males. No difference of growth was detected between flight and ground females after metamorphosis. All differences between flight and ground animals disappeared 1 year after landing. We conclude (1) that limited spatial and nutritional conditions during the mission period caused developmental retardation, and (2) that the thyroid gland of Xenopus is susceptible to spatial environment, in particular, during the period of beginning activation.
Research Containing: Metamorphosis
Suboptimal evolutionary novel environments promote singular altered gravity responses of transcriptome during Drosophila metamorphosis
BACKGROUND: Previous experiments have shown that the reduced gravity aboard the International Space Station (ISS) causes important alterations in Drosophila gene expression. These changes were shown to be intimately linked to environmental space-flight related constraints. RESULTS: Here, we use an array of different techniques for ground-based simulation of microgravity effects to assess the effect of suboptimal environmental conditions on the gene expression of Drosophila in reduced gravity. A global and integrative analysis, using "gene expression dynamics inspector" (GEDI) self-organizing maps, reveals different degrees in the responses of the transcriptome when using different environmental conditions or microgravity/hypergravity simulation devices. Although the genes that are affected are different in each simulation technique, we find that the same gene ontology groups, including at least one large multigene family related with behavior, stress response or organogenesis, are over represented in each case. CONCLUSIONS: These results suggest that the transcriptome as a whole can be finely tuned to gravity force. In optimum environmental conditions, the alteration of gravity has only mild effects on gene expression but when environmental conditions are far from optimal, the gene expression must be tuned greatly and effects become more robust, probably linked to the lack of experience of organisms exposed to evolutionary novel environments such as a gravitational free one.
To investigate the effects of cosmic radiation and microgravity on embryogenesis and organogenesis in Bombyx eggs, two different stages of eggs, the early stage after oviposition and the diapause-terminated eggs, were loaded on the US Space Shuttle/Atlantis (STS-84) for a 9 day flight. More than 85% of the early stage eggs hatched in the flight sample and the ground control. In the diapause-terminated eggs, the percentage of unhatched eggs were 43% in the ground control and 56% in the flight sample. In these eggs, uncompleted embryonic reversal was observed two-fold higher percentage in the flight sample than in the ground control. The incidence of abnormality such as the larvae with segmental fusion and the appearance of abnormal crescent marking in the flight sample was significantly higher than that in the ground control. This was also observed in the 1st and 2nd filial generation of the flight sample. From these results, unsuccessful blastokinesis and the abnormal appearance was discussed in relation to cosmic radiation and microgravity.