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Development of the gravity-sensing organs in the Japanese red-bellied newt, Cynops pyrrhogasterPre-mated adult female newts and fertilized eggs will be flown on the International Microgravity Laboratory-2 flight, schedule for 1994. One objective of the flight will be to observe the influence of microgravity on the development of the gravity-sensing organs in the inner ear. These organs contain sensory hair cells covered by a layer of dense stones (otoliths). Gravity and linear acceleration exert forces on these masses, leading to excitation of the nerve fibers innervating the hair cells. If the production of the otoliths is regulated to reach an optimal weight, their development would be abnormal in microgravity. Ground-based control experiments are reported describing the developmental sequence in which the otoliths and their associated sensory epithelium appear and increase in size. Three-dimensional reconstruction of serial sections through the otic vesicle of newt embryos at stages 31 through 40 demonstrate the first appearance, relative position and growth of the otoliths. In adult newts, the otoconia in the utricle appear similar to mammalian otoconia, which are composed of calcite. The newt saccular otoconia are at least 99% aragonite, as is found in most aquatic species. Reports of experiments in which fertilized frog eggs were flown on a Russian Cosmos mission conclude that the utricular otolith is increased in volume, whereas the saccular otolith maintains normal size, suggesting that at least the utricular weight might be regulated.
Document ID
19950051013
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Wiederhold, Michael L.
(Univ. Texas, San Antonio, TX US, United States)
Yamashita, Masamichi
(Inst. Space & Astronautical Sci. Sagamihara, Japan)
Asashima, Makoto
(Yokohama City Univ. Yokohama, Japan)
Date Acquired
August 16, 2013
Publication Date
January 1, 1992
Publication Information
Publisher: ISTS Editorial Board
Subject Category
Life Sciences (General)
Accession Number
95A82612
Distribution Limits
Public
Copyright
Other

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