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Animal Biology

Noise pollution damages the hearing of cephalopods

The Laboratory of Applied Bio-Acoustics of the Polytechnic University of Catalonia has developed a study showing that low-frequency noise produced by large-scale human activities at sea causes acoustic trauma to cephalopods, a class of mollusks, that leads to severe injuries to their auditory structures

STAFF | APRIL 11TH, 2011

An 'Octopus vulgaris', a member of the cephalopod class

For a number of years, the Polytechnic University of Catalonia has analyzed how noise pollution at sea causes physical and behavioral changes in many species, especially to dolphins and whales that use sound in their daily activities such as hunting and navigating. Now, the LAB has shown that noise, in this case at low frequencies, produced by offshore activities is also causing damage to other marine species such as cuttlefish, squid and octopus.

In 2001 and 2003, dead giant squid appeared off the coast of Asturias in northern Spain just after ships fired a series of shots with compressed air guns for geophysical surveys. This suggests that their deaths may have been related to excessive sound exposure.

In the study, the LAB team of researchers led by Michel André exposed 87 cephalopods from four different species (Loligo vulgaris, Sepia officinalis, Octopus vulgaris and Illex coindeti), to low-frequency sounds, between 50 and 400 hertz. As explained in the article published in Frontiers in Ecology and the Environment, the journal of the Ecological Society of America, the animals suffered acoustic trauma in the form of severe injuries to their auditory structures.

To study the effects of exposure to loud sounds similar to those experienced by the giant squid in Asturias, the researchers analyzed the animals’ statocysts. Statocysts are balloon-shaped structures that help invertebrates maintain balance and position. These organs, which are filled with fluid, are similar to the vestibular apparatus in mammals and, as demonstrated in this study, are important in the perception of low-frequency sounds by cephalopods.

The injuries affect their ability to hunt, avoid predators and even breedImmediately after exposure to low-frequency sounds, the researchers found that cephalopods showed damage to the hair cells in their statocysts, which are the sensory cells of the auditory system of these animals. Over time, the nerve fibers become inflamed and eventually holes appear. The injuries grew more severe over long-term exposure to noise.

As explained by André, since short-term exposure caused severe acoustic trauma to these animals, the impact of high-frequency noise on a continuous basis can be considerable. And since statocysts are responsible for the balance and spatial orientation of cephalopods, the damage caused by noise to this organ is likely to affect the animals’ ability to hunt, avoid predators and even breed. In other words, according to André, it threatens their very survival.

The article is available on the LAB website as of 17:00.
www.lab.upc.es / frontiers

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