Beneath the waves of the Pacific and Indian oceans lives a small creature called the smooth fan lobster. The little crustacean has a habit of dining upon venomous jellyfish, and researchers are trying to figure out how it manages to live on such a dangerous diet.

These aren't the big red lobsters you might be used to seeing (the ones scientists refer to as "true lobsters"); instead, this species belongs to a family called the slipper lobsters. The flat, spider-like larval stage of this crustacean is known as a phyllosoma and they are truly marine daredevils. These lobsters-in-the-making ride around on venomous jellyfish while eating them alive, stinging tentacles first. That's hardcore.

For Kaori Wakabayashi, a marine scientist at Hiroshima University, studying the eating habits of the little phyllosomas is important it's key to figuring out how to farm these animals sustainably. Lobsters might be tasty, but they're notoriously difficult to raise in captivity, and finding out more about their life cycles could change that.   

The research, explains Wakabayashi, is step towards finding better food sources for farmed lobsters and other marine life. It might be possible, for example, to raise some lobster species on jellyfish alone and that's an increasingly plentiful resource in our oceans.

"Farmed marine species are often fed sardines, which has contributed to a dramatic decrease in global sardine populations. In the future, artificial food will empower farmers to provide their lobsters with convenient, sustainable and safe nutrition," said Wakabayashi in a statement.

The little lobsters are covered with protective chitin on the outside, and even inside their intestines. But the middle section of their gut has no such armour so how do they survive their habit of nibbling on deadly jellyfish? 

Jellyfish stingers come armed with microscopic structures called nematocysts. When triggered, the nematocyst explosively projects a needle-like tubule that injects venom into the target. As you can imagine, this is equally useful against the jellyfish's predators and its prey. What's more, these nematocysts can fire what scientists call "discharging" even after the jellyfish has died, or when a tentacle has been detached.

To figure out how the lobsters survive swallowing deadly stingers that could go off at any moment, scientists looked to other corners of the animal kingdom for answers. Some marine species like the bearded goby seem simply immune, or at least resistant, to the stings. Nudibranchs, on the other hand, also eat jellyfish stingers, but their digestive system handles them so carefully that the nematocysts aren't discharged in the process.

Does the smooth fan lobster have similar strategies? To find out if the animals were resistant to stings, the researchers did pretty much what you'd expect: they injected lobsters with venom from a jellyfish that lives in the same oceans, a large species called Nomura's jellyfish. Nine out of ten tested lobsters died. Clearly no resistance here.

So how were the stingers passing harmlessly through the crustaceans' digestive tracts? The answer was in their poop. Researchers fed the lobsters a species of jellyfish called the Japanese sea nettle, and after examining their fresh faeces, they found the nematocysts neatly wrapped up in a thin membrane that the venomous needles couldn't penetrate, even when accidentally discharged. This membrane seems to be produced in that unprotected middle section of the lobsters' gut. It seems these hardy critters have it all covered (literally!). 

This study is a step in the right direction for sustainable farming. "Based on the contents of their faeces, 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.


Top header image: Geoffrey Gilmour-Taylor, Flickr