Fishy behavior
A fish, specifically a mummichog (Fundulus heteorclitus), was sent to Skylab in 1973. Scientists were seeking to study the ways in which vestibular function, which controls balance in normal gravity, may be compromised in space. The tiny fish, along with a batch of fish that developed from embryos brought to space, exhibited strange swimming behavior, moving in loops. “The fish were probably responding to signals from extremely fine hairs in their otolith [a vestibular organ in fish] which straighten out in the absence of gravity,” according to NASA. “They reacted by swimming in a forward loop which was distorted into a sideways loop by the tendency to keep their backs to the light.” The fish, it would seem, were responding to light (i.e. visual cues) in the absence of gravity, which would normally allow them to discern up from down.
