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Protective Coating Lets Lobsters Avoid Stings When Eating Jellyfish

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Researchers have discovered that lobsters protect themselves from stings when they eat jellyfish by coating stingers in a protective membrane.

Led by Kaori Wakabayashi, researchers from the Hiroshima University carried out their work to learn more about the feeding habits of lobsters, bolstering aquaculture efforts to facilitate sustainable lobster farming. Lobsters are not farmed at the same scale as fish, crab or shrimp because there is little understanding of their nutritional needs.

"In the future, artificial food will empower farmers to provide their lobsters with convenient, sustainable and safe nutrition regardless of weather, locality or the availability of other marine resources," said Wakabayashi.

As larvae, lobsters ride around on jellyfish, eating their host as they do so. To counteract the venom from jellyfish stingers, lobster intestines are lined with chitin, the same hard plates covering lobster bodies outside. However, the middle third of lobster intestines don't have this protective shell, exposing a lobster's midgut to stingers.

To find out how lobsters protect themselves from stingers, Wakabayashi and colleagues fed lobsters they cultivated in the lab with the tentacles of the Japanese sea nettle. When they examined the lobsters' feces, they discovered the stinging cells in the feces, which had been tightly wrapped in a peritrophic membrane. While this membrane normally allows molecules to move both ways, it appeared strong enough to keep the stingers from hurting a lobster.

However, lobsters are not immune to the effects of jellyfish venom. In another experiment, the researchers injected lobsters with jellyfish venom and observed a drop in lobster grooming, specifically where lobsters sweep their bodies with specialized front legs.

Jellyfish are not willing, of course, to provide lobsters with free rides and meals so they do what they can to fight back, flinging copious amounts of mucus at their enemy. Covered in enough mucus, lobsters will develop fatal bacterial infections. However, they've also adapted to jellyfish fighting back, using their specialized front legs to remove the mucus from their bodies.

Based on further analysis of the feces samples, the researchers saw that lobsters appear to digest only fluid-type food. If artificial food for lobster farming is to be developed, this is a crucial discovery.

In June, the European Union issued a proposal banning the importation of American lobsters. The move was initiated after 32 American lobsters were found in Sweden's waters and deemed invasive. U.S. fishery officials, however, countered that the proposal has no scientific basis.

Some of the American lobsters were also found to be carrying eggs. With Scandinavian lobsters being small and delicate, any hybrids formed will result in negative genetic effects, said Asa Romson, Swedish climate and environment minister.

Photo: Ratha Grimes | Flickr

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