A new study published in the journal PLOS ONE by researchers from the University of Bordeaux in France highlights how oysters might be more responsive to stimuli than initially thought. In particular, they appear to close their protective shells at the propinquity of low-frequency noises.

Image Credit: Jean-Charles Massabuau

Oysters' responses to these sound frequencies could be a self-defense mechanism that guards them against numerous predators, but it also notifies them of when to open their shells in time for thunderstorms and tides.

As crucial as this response seems to be for the everyday life of an oyster, the research underscores the potential implications this has for the mollusks as marine sound pollution reaches record highs.

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To better distinguish which sound frequencies the oysters respond to the most, researcher Jean-Charles Massabuau and colleagues studied the effects of different sounds on 32 oysters in a lab-based setting. They summoned the help of an underwater loudspeaker that played several sound frequencies ranging from 10-20,000 Hertz.

The team watched and waited as the oysters reacted to different sounds emanated from the loudspeaker. They paid especially close attention to specific details, such as the number of oysters responding to the sounds, the speed at which they closed their shells, and just how far they closed them.

"Noise pollution in the oceans is a growing problem, and we have all heard about its impact on whales," Massabuau said. "But the oceans are full of different animal types. What are their sound perception capacities? This paper talks about the sense of hearing in oysters and they can hear a lot from 10-1000 Hz."

The oysters seemed to slam the door on sound frequencies within 10-1,000 Hertz but were most sensitive to lower-frequency sounds occurring in the 10-200 Hertz range. Higher-frequency sounds had little or no bearing on the oysters’ behavior.

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While oysters don’t have literal ears per se, they can still identify vibrations from specific sound frequencies. Low-frequency sounds, like those emitted from a subwoofer, expel noticeably more vibration than high-frequency sounds do. That said, it's not difficult to understand why oysters can detect low-frequency sounds so much more efficiently.

Regrettably, the research underscores how many of humankind's activities produce low-frequency sounds that could tamper with this behavior. Loud passerby ships, oil drilling, seismic research, wind turbines, and more are each contributory factors.

The analysis exposes how hoise pollution masks predatory noises and prevents oysters from detecting nearby threats. Oysters may also confuse these sounds for thunderstorms or tides, and open their shells at dangerous times.

Our influence on the marine world, as indirect as it may seem at first glance, is something we need to consider for the sake of preserving Earth’s beautiful wildlife.

Source: New Scientist