If the black long sea cucumber (Holothuria leucospilota) was a superhero, they might have quite a bit in common with a famous blue and red web slinger from Queens, New York. This sea cucumber has a comedic, but incredibly useful, way to ward off the hungry predators that stalk these strange creatures. When provoked, they will tear a hole in the wall of their butts and shoot out a tangle of sticky, noodle-like goo.
The process is described in a study published April 10 in the journal Proceedings of the National Academy of Sciences (PNAS) and the unique defense mechanism can entangle and stop predators in their tracks. The expendable tangles are called the Cuvierian organ and look like a mass of white spaghetti that the cucumber has expelled from its butt.
The organ is made of amino acids in repeating sequences. These proteins give the organ some strength and have unique arrangements of the proteins. Repeating amino acid sequences are also found in silkworm threats and spider webs.
The Cuvierian organ is at the bottom of the sea cucumber’s respiratory tree, where the cucumbers breathe as well as poop. The organ contains hundreds of dangling tubes, and the sea cucumber can self-amputate it and fully regrow it in as quick as 15 days.
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For the study, the team followed the molecular pathway that triggers the Cuvierian organ’s deployment, and found that piercing the area with a needle or grazing the skin activated the goopy sensation. However, applying direct pressure didn’t cause the reaction.
These tubules can expand up to 20 times their original length with water pumping inside from the respiratory tree. The tubules become sticky upon contact with any surface and cling to the who or whatever is touching it. After being entangled in the butt goo, the aggressor sometimes even dies of starvation.
Once a sea cucumber is safe from attack, it will likely crawl away from the deadly butt goo web. Scientists often find them partially hidden under clumps of seaweed, corals, or boulders. They then go back to their usual behaviors, filtering organic matter from the sand and recycling nutrients like calcium back into the water by pooping them out. Corals and other animals can then eat up the nutrients.
[Related: Watch these tiny bugs catapult urine with their butts.]
The team also found amyloid-like patterns in the proteins located within the Cuverian organ’s outer membrane. The brains of human patients with Alzheimer’s disease typically contain higher levels of amyloid plaques, but these proteins are used by marine organisms like barnacles as a strong adhesive.
“This study provides the first genomic insights into defensive ensnarement in a representative species of [sea cucumber],” they write.