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Does Altered Gravity Influence Body Dimensions and the Development of Head Cartilage in Frogs? M. Rodriguez1, T. Gaul1, H. Grisback2, D. Slusarski2, W. Olson1, and D. Wiens1.  1Dept. of Biology, Univ. N. Iowa, Cedar Falls, IA, and 2Dept. of Biol. Sciences, Univ. Iowa, Iowa City, IA.

   In vertebrate embryos cranial neural crest cells (NCCs) migrate from the dorsally closing neural tube into the head to form the mandibular, hyoid and gill arch cartilages, establishing the larval head skeleton.  During this period, initially spherical amphibian embryos elongate and flatten side-to-side, and eventually grow in size.  Changes in the force of gravity are known to cause biological effects during this sensitive early period.  Embryonic cellular processes, including macromolecule synthesis, shape change, migration, signaling and differentiation, may adjust or become deranged with alterations in gravity.  To investigate these effects, we cultured Xenopus embryos in the Slow-Turning Lateral Vessel (STLV) from yolk plug stage (12 hr post-fertilization) to 4 days and then used image capture and analysis to measure body and head cartilage sizes.  We found that tadpoles that developed in the STLV were longer from snout to vent, had longer tails, and had larger head areas than controls.  Their head cartilages were also larger, but if corrected for head size, were considerably smaller than corrected controls.  Analysis with NCC-specific molecular probes is underway. We conclude that STLV-simulated microgravity has both qualitative and quantitative effects on the development of the functional larval skeleton in frogs. 

(Supported by a Cooperative Activity Grant from the Iowa Space Grant Consortium.)