Natures wonders: sea cucumber self-protection (Introduction)

by David Turell , Wednesday, July 06, 2022, 15:56 (869 days ago) @ David Turell

They produce poisons for others but they are protected:

https://www.the-scientist.com/news-opinion/how-the-sea-cucumber-defends-itself-from-its...

"Despite being soft, squishy, and slow-moving, sea cucumbers (Class Holothuroidea) are surprisingly tough. They scavenge in harsh, rapidly changing conditions on the ocean floor, under the constant threat of toxic bacteria. To protect themselves against predators and pathogens alike, sea cucumbers produce defensive toxins called saponins, as do their close cousins, starfish. However, new research finds that sea cucumbers are the only echinoderms—and among the only animals on Earth—that produce chemicals called triterpenoid saponins, which don’t poison the sea cucumbers themselves thanks to their unique metabolic pathways.

"A study published Monday (June 27) in Nature Chemical Biology finds that sea cucumbers have evolved a way to synthesize these saponins with different enzymes than those used by their echinoderm cousins and the vast majority of other animals. In doing so, they’ve evolved a mechanism that makes them immune to their own saponins.

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"...since sea cucumbers lack any adaptive immunity and must rely on their innate defenses to survive, “it’s not so surprising that . . . sea cucumbers evolved something special” to defend themselves.

"Previously, scientists knew that sea cucumbers produced triterpenoid saponins, which are more commonly found in plants than in animals. These chemicals bind to cholesterol molecules on cell membranes and rapidly cause death. In the new study, the researchers found that the sea cucumbers don’t produce cholesterol and have very little of it on their membranes, which allows them to remain unfazed by saponins.

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"The team discovered that the cucumber OSC genes produced two sterol-like molecules, both of which were involved in triterpenoid production. These molecules also converted compounds into the cholesterol-like molecules that are present in the sea cucumber cell membranes. The molecules function similarly to cholesterol, but their differences help the animals avoid poisoning themselves with saponins."

Comment: another example of an irreducibly complex mechanism with so many interlocking requirements, it must be created all at once, not step by step by chance. This must be designed.