Among sailors an old observation has long circulated: before a storm, jellyfish leave the shore for deeper water. In an animal with no brain, eyes or ears this sounds almost mystical — but nature, it seems, has a working explanation, and it is again about infrasound.
An organ that senses the motion of water
Around the rim of their bell, jellyfish have statocysts — tiny balance organs. Inside lies a solid grain (a statolith) that presses on sensitive hairs and tells the jellyfish where "down" is and how the water is moving. The same system can pick up low-frequency vibrations — and therefore infrasound, which a storm drives ahead of itself.
The direct sensitivity of cnidarians (relatives of jellyfish) and cephalopods to low-frequency sound has been shown experimentally: after exposure to low frequencies, it was precisely their statocysts that were damaged.1 This is a weighty argument that the "balance organ" also works as an "ear" for infrasound.
That jellyfish react to low frequencies is an established fact. But "a jellyfish predicts a storm by infrasound" is so far a plausible hypothesis, not a proven theorem. It is exactly such gaps that are interesting to close in the laboratory.
From observation to technology
If jellyfish "hear" low frequencies, the inverse idea arises: could a swarm be gently deterred with sound, without harming it? That would turn a folkloric observation into a humane technology for protecting beaches, water intakes and yachts. We are developing this as a separate research branch.
The jellyfish's ability to sense low-frequency vibration via statocysts is documented (Solé et al., 2016 — already cited in this article). But "jellyfish predict storms days ahead" remains an attractive hypothesis and a source of bionics inspiration, not a proven, field-validated forecasting fact.
- A jellyfish has no brain, no heart and no lungs — but it does have statocysts, distant "relatives" of our vestibular apparatus.
- Swarms of jellyfish have more than once shut down nuclear and other power plants by clogging cooling water intakes — in France, Sweden, Japan.
- Jellyfish are about half a billion years older than the dinosaurs and have survived every mass extinction.
HERD is running an honest, step-by-step project for a humane infrasound jellyfish deterrent — with the emphasis on "ward off, do not harm". Read about the "jellyfish deterrent" R&D →
Sources for this article
- peer-reviewed Solé M. et al. (2016). Evidence of Cnidarians sensitivity to sound after exposure to low frequency noise. Scientific Reports 6. nature.com