Ramisyllis is a bristle worm that lives inside the water passages of a sponge called Petrosia in a shallow reef off the coast of northern Australia. Its lone, unremarkable and rather lethargic head is buried deep in the sponge. Shortly after that things get weird.
Its body begins to branch repeatedly and without pattern. The legion resulting posteriors may protrude into the seawater through natural holes in the sponge and amble along its surface. One “small” sponge observed by scientists was festooned with more than 100 crawling worm fannies, sometimes more than 10 to a single opening. Although sponges are many remarkable things, sentient is not one of them, and that must surely be counted as a win here.
Further, each branch contains its own set of internal organs. According to thefirst detailed anatomical studyof these worms, published this year in the Journal of Morphology by a team from Spain, Australia and Germany, these organs are in no way different from that of the unbranched juvenile. They further found that the worm’s gut is continuous throughout the entire labyrinthine animal—but conspicuously empty. No sponge tissue has ever been found inside, nor food particles of any kind.
Jennifer Frazer, “One Head, 1,000 Rear Ends: The Tale of a Deeply Weird Worm” at Scientific American (August 8, 2021)
Animals adopt the lifestyles of plants (sea anemone?) and fungi but are there any instances of plants or fungi adopting the lifestyles of animals? If not, why not?
See also: Botanist Margaret Helder asks: How can a “simple” or “primitive” sponge surprise engineers with its optimal physics? Helder: A team of Italian and American scientists researching this topic declared that the sponges display “exceptional structural properties” which enable them to thrive. In fact, their study reveals “mechanisms of extraordinary adaptation to live in the abyss.”