Sea Cucumber Shoots Silky, Sticky Substance From Its Butt to Defend Itself From a Crab [Watch]

Sea cucumber has a unique self-defense mechanism. It has the capacity to release a unique substance, which is a whole organ, to protect itself.

Sea Cucumber and Its White Stringlike Tubes

While some lizards shed their still-moving tails to ward off predators, sea cucumbers take this tactic a step further. A silky, sticky material that some frightened sea cucumbers squirt out of their behinds is a complete organ. This can be observed in the video shared below as the sea cucumber defends itself from a crab.

The tangle of tubules, which resembles intestines but developed from an invertebrate's respiratory system, regenerates itself after use like a lizard tail.

In a recent study, researchers examined the black sea cucumber's genome to see how its Cuvierian organ, the stringlike tubules, works at the molecular level, Science News reported.

According to Ting Chen, a biologist at the South China Sea Institute of Oceanology in Guangzhou, the Holothuria leucospilota, also known as the black sea cucumber, is the most prevalent species of sea cucumber in the South China Sea. They are interested in learning this sea cucumber's evolutionary advantage, allowing its population to grow so rapidly and predominately.

As a result, the scientists examined the sea cucumber's full genome or genetic manual. Since the Cuvierian organ is such an unusual structure, they concentrated on genes from it. Afterward, the group utilized a tool called AlphaFold to forecast which proteins would be produced from Cuvierian organ genes. New forms of cell surface receptors that were unexpectedly predicted proteins might be involved in removing the organ.

Sea Cucumber's Silk Tubules Are Comparable to Spider Silk

The research team also discovered that the "silk" proteins in sea cucumber tubules are comparable to spider silk, comprising extended, repeating chains of amino acids rather than the amino acid sequences observed in spider silk.

The study suggests that these long repeats may represent a shared structural feature even if silklike proteins developed independently.

Additionally, according to Chen, proteins with characteristics resembling amyloids are responsible for the organ's stickiness, which stops sea cucumber predators like fish, crabs, and starfish in their tracks. Numerous human disorders, especially neurodegenerative ailments like Alzheimer's, are linked to amyloids.

Belgian biologist Patrick Flammang, who was not involved in the work, said the paper reveals unexpected proteins unique to the Cuvierian tubules. It also offers a ton of information that can be used to address other queries about the mysterious organ's evolutionary history.

And a high-quality genome is important in other ways as well. Genomic data is required to research the endocrine, immunological, reproductive, and digestive systems of H. leucospilota. Chen claims that the team is currently examining the genetics underlying how sea cucumbers detect light and digest food.

The study was published in the Proceedings of the National Academy of Sciences on April 10.

What Is Cuvierian Tubule?

Cuvierian tubules are unusual organs found in various sea cucumber species that are all members of the Holothuriidae family. On the basis of their gross exterior morphology, they can be either lobulated or smooth.

Actinopyga is the only genus where lobulated tubules are seen. They never eject and are not sticky.

In contrast, smooth tubules are observed in the genera Bohadschia, Holothuria, and Pearsonothuria, where they typically form white, sticky threads that serve as a defense mechanism. This is what's observed in the black sea cucumber.

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