EMBRYONIC DEVELOPMENT OF AMPHIBIANS IN WEIGHTLESSNESS (AQUARIUS)
Research Area: Animal Biology - Vertebrates
Expedition(s): 3
Principal Investigator(s): ● Eberhard R. Horn, University of Ulm, Ulm, Germany
● Christian Dournon, Universite Henri Poincare, Nancy, France
RESEARCH OBJECTIVES
The Embryonic Development of Amphibians in Weightlessness (Aquarius) investigation studies
whether altered gravity affects vestibulocular and spinal motor systems in a correlated manner
on xenopus laevis embryos.
RESULTS
After exposure to altered gravity, each tadpole was tested for its
roll-induced vestibulocular reflex (rVOR) and 3 hours later it was
tested for the neuronal activity recorded from the ventral roots
during fictive swimming. It was observed that weightlessness
affected ventral root activity during fictive swimming and rVOR.
In particular, ventral root activity changes included a significant
decrease of the rostrocaudal delay and a significant increase of
episode duration. The rVOR-amplitude was transiently
depressed. All modifications of the rVOR and ventral root-activity
recovered to normal levels within 4 to 7 days after termination of
altered gravity. Significant correlations between the rVOR
amplitude and ventral root activity during the recording period
have been observed in both tadpoles with or without altered
gravity experience. The data are consistent with the assumptions
that during this period of life, which is characterized by a
progressive development of vestibulocular and vestibulospinal
projections (i), weightlessness retards the development of
ventral root activity while hypergravity accelerates it; (ii) that
weightlessness retards the rVOR development while
hypergravity caused a sensitization, and that (iii) altered gravity
induced changes of ventral root activity during fictive swimming
have a vestibular origin.
PUBLICATION(S)
Boser S, Dournon C, Gualandris-Parisot L, Horn ER. Altered gravity affects ventral root activity
during fictive swimming and the static vestibuloocular reflex in young tadpoles (Xenopus
laevis). Archives Italiennes De Biologie. March 2008; 146(1):1-20.
Horn ER, Dournon C. Experiences from a French-German project - on the integration of pupils in
an actual space experiment. Microgravity Science and Technology. 2007;19(5-6):230-234. doi:
10.1007/BF02919488.
Vestibuloocular reflex in
Xenopus laevis. The numbers
inside the frames indicate that
the tadpole shown with its
frontal view is lying either
horizontally (000°) or on its
right side (090°) inducing the
asymmetric posture of the
eyes. E.R. Horn image.