Research Highlights: A Roundworm May Help Us Explain How We Perceive Gravity

A Roundworm May Help Us Explain How We Perceive Gravity

  • Humans depend on gravity to determine orientation and maintain balance.
  • Gravity is important for life to exist on Earth.
  • However, the effect of gravity at the molecular level is poorly understood.
  • Among animals, anatomical differences are clearly evident but there is notable conservation across different animals at the molecular level.
  • Caenorhabditis elegans is appropriate for discovering genes that may help identify gravity sensing mechanism at the molecular level.
  • C. elegans is a free-living nematode or roundworm that lives in temperate soil environments.[1]
  • Half of C. elegans‘ genes are similar to humans which allows genetic studies to determine genes responsible for the similar traits in humans.
  • No study has been reported that C. elegans can detect the direction of gravity.
  • A team in Penn Engineering led by Professor Haim Bau and Professor David Raizen did a research that may explain the mystery of gravity sensing.
  • Researchers found that motile C. elegans swim in the direction of gravity while immobile C. elegans do not.
  • Regardless of the density of a solution, C. elegans position themselves downward.
  • Gravitaxis is not significantly affected by the animal’s gait but requires sensory cilia, dopamine transmission, as well as motility.
  • Gravitaxis is the directional movement of an organism in response to gravity.[2]
  • Gravitaxis does not require genes related to body touch response.
  • Gravitaxis is not mediated by passive forces like the hydrodynamics of the solutions where the C. elegans are swimming in.
  • The results suggest that gravitaxis is mediated by active neural processes that involve dopamine and sensor cilia.
  • C. elegans can be used as a genetically tractable system for research studies involving molecular and neural mechanisms of sensing gravity.

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Chen, WL., Ko, H., Chuang, HS. et al. Caenorhabditis elegans exhibits positive gravitaxis. BMC Biol 19, 186 (2021).