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How Lobsters Eat Jellyfish Without Harm From Venomous Stingers

Their secret: They wrap their feces in a protective membrane for safe passage of the stingers through their gut

Hiroshima University scientists examined lobster feces to discover that the crustaceans surround their servings of jellyfish in protective membranes that prevent the stingers from injecting their venom. The results inform aquaculture efforts to sustainably farm lobsters, the university said in a news statement.

Dr. Kaori Wakabayashi is the leader of a research group at Hiroshima University and has studied lobster development with the goal of creating a food for farmed lobsters.

“Lobsters are not farmed on the scale of shrimp (prawns), crab, or fish because their development and nutritional needs remain poorly understood,” the university said in a news statement about Wakabayashi’s work.

Lobsters grow for years before becoming a red-shelled main meal for humans, the university explained. “In their early life stages, the larvae of slipper and spiny lobsters are nearly transparent and about the size of an adult’s thumb nail. Lobster larvae ride around the ocean on the bodies of jellyfish while eating them alive, including the venomous portions of the tentacles.”

Farmed marine species are often fed sardines, which has contributed to a dramatic decrease in global sardine populations, the news statement noted. “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. Knowing what the lobsters ate also ensures greater food safety for people,” said Wakabayashi.

Armor-plated lobster intestines leave midgut vulnerable to jellyfish stingers

“Lobsters’ intestines are lined with the same hard plates of chitin that cover the outside of their solid bodies,” Hiroshima University said. “These plates probably defend the lobsters from jellyfish stings both on the surface and inside of their bodies. However, the intestinal armor does not cover the middle third of the length of the lobsters’ intestines, leaving their midgut exposed to the stingers.”

The stinging cells of Japanese sea nettles (Chrysaora pacifica) behave like extendable syringes, able to poke out and inject venom into the jellyfish’s prey.

The research team raised lobster larvae and jellyfish in the laboratory, fed lobsters (Ibacus novemdentatus) a meal of only Japanese sea nettle tentacles,  then suctioned up the lobsters’ fresh feces.

Under the microscope, researchers noticed the feces pellets were wrapped tightly in layers of a peritrophic membrane, Hiroshima University said. “These membranes usually allow certain small molecules to travel in both directions, but are apparently strong enough to prevent the stingers from reaching the lobster.”

“Based on the contents of their feces, we think that the lobster larvae only digest fluid-type foods, which is vital to know as we develop an artificial food for farmed lobsters to grow efficiently and healthily,” said Wakabayashi.

In another experiment, researchers confirmed that the lobsters are not immune to direct injections of jellyfish venom. When lobsters were injected with venom, researchers noticed that the lobsters’ grooming behavior — sweeping their bodies with specially adapted front legs — was the last movement lobsters stopped making. “Frequent grooming could be essential for lobsters’ survival, possibly by preventing jellyfish mucus and the bacteria that comes with it from settling on the lobsters’ bodies,” the university statement said.

Post prepared from materials made available by the University of Hiroshima.

12418031_10153900711084116_8462971761216697621_nDavid Braun is director of outreach with the digital and social media team illuminating the National Geographic Society’s explorer, science, and education programs.

He edits National Geographic Voices, hosting a global discussion on issues resonating with the Society’s mission and major initiatives. Contributors include grantees and Society partners, as well as universities, foundations, interest groups, and individuals dedicated to a sustainable world. More than 50,000 readers have participated in 10,000 conversations.

Braun also directs the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship

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