Size and cell number of the utricle in kinetotically swimming fish: a parabolic aircraft flight study.

Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness (SMS, a kinetosis). Since it has been repeatedly shown earlier that some fish of a given batch also reveal a kinetotic behavior during PAFs (especially so-called spinning movements and looping responses) and due to the homology of the vestibular apparatus among all vertebrates, fish can be used as model systems to investigate the origin of susceptibility to motion sickness. Therefore, we examined the utricular maculae (they are responsible for the internalization of gravity in teleosteans) of fish swimming kinetotically at microgravity in comparison with animals from the same batch who swam normally.