Researchers have been observing baby lobster poop in order to figure out how these marine snappers are able to devour venomous jellyfish without their intestines being stung. Reporting their findings in the journal Plankton and Benthos Research, the study authors from Hiroshima University describe how the poo pellets were coated with a special membrane that allows certain substances to pass through while keeping the lobsters protected from the jellyfish stingers.
The larvae, or phyllosoma, of the fan lobster cruise around the ocean with a voracious hunger, which they satisfy by attaching to the bodies of jellyfish and devouring them alive. However, scientists have for some time struggled to get their heads around how these tiny lobsters-in-training eat their prey’s stingers without succumbing to the venom.
Jellyfish, like the Japanese sea nettle, are armed with what the study authors describe as “venom-filled explosively penetrant cnidae,” which are like tiny harpoons that are fired into victims’ bodies, filling them with toxins. Yet for some reason, the intestines of lobster phyllosoma appear not to be affected by this weaponry.
To investigate, the researchers raised fan lobster larvae in the lab, feeding them exclusively on Japanese sea nettle jellyfish. When examining the tiny crustaceans’ feces, they discovered that this excrement was encased in a peritrophic membrane, which keeps the cnidae under wraps and stops them coming into contact with the intestinal wall.
"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," explained study co-author Kaori Wakabayashi.
To confirm that the lobsters aren’t simply immune to jellyfish venom, the researchers then injected phyllosoma with crude tentacle extract, and found that this caused nine out of ten to die. As such, it seems likely that the larvae do not digest the cnidae or their contents at all, with their poop membranes being the most obvious source of protection.