Recent approaches in the analysis of weightlessness effects on arthropod development.

The concept of Biological Development refers to the extremely complex process by which every biological organism reproduces starting from a huge single cell, the fertilized egg. It includes all aspects of cellular and intercellular structure and function. In spite of many recent advances, especially at the molecular and genetical level, we are still far from fully understanding the details and mechanisms at work in developmental systems.

Arthropod model systems for studying complex biological processes in the space environment.

Three arthropod systems are discussed in relation to their complementary and potential use in Space Biology. In a next biosatellite flight, Drosophila melanogaster pre-adapted during several months to different g levels will be flown in an automatic device that separates parental from first and second generations. In the same flight, flies will be exposed to microgravity conditions in an automatic unit in which fly motility can be recorded.

Effect of diets containing adenosine, guanosine, inosine or xanthosine on the nucleotide content of Artemia. Influence of mycophenolic acid.

Artemia uses the stored diguanosine tetraphosphate as a source of adenine and guanine nucleotides during development from the encysted gastrula to the free swimming larva. Further development of the larvae depends on a dietary source of purine rings. We have investigated the growth of Artemia in axenic cultures supplemented with 0.

Guanylate requirement for patterning the postcephalic body region of the brine shrimp Artemia.

Mycophenolic acid (MA) reduces growth and survival rates of Artemia larvae fed hypoxanthine. The inhibitory effect of MA is suppressed by dietary guanosine as expected for inosinate dehydrogenase inhibition. Pulse MA treatments lasting 24 h imposed on larvae from 24 to 96 h posthatch result in the production of abnormal adults with thoracic, genital or abdominal defects.

Heat induced developmental uncoupling of mesoderm from ectoderm and endoderm germ layer derivatives during Artemia postembryonic segmentation.

Taking advantage of the fact than segmentation inArtemia is largely a postembryonic process making it more susceptible to environmental influences, heat treatments ofArtemia newly-hatched nauplii were shown to induce a severe inhibition of mesodermal structures, without apparently affecting the corresponding ectodermal and endodermal derivaives. This inhibition was reversible and with enough time the missing mesodermal structures developed. These results indicate that ectoderm and endoderm development can proceed without neccessarily a concomitant mesodermal differentiation, which in turn can be largely uncoupled from that of the rest of the germ layer derivatives.