In April 2018, underwater photographer Ryo Minemizu saw a beetle-sized creature bobbing about 50 feet underwater off the shores of Okinawa, Japan. The thing looked like a jellyfish, a yolk-like center with dangling tentacles. Minimizo posted photos of the creature on social media, but no one was able to decipher the mysterious swimmer. They couldn’t even look up its phylum, which is a taxonomic class ranked just below the kingdom, meaning it’s incredibly broad (examples of phyla include arthropods, molluscs, and chordates). But now, in a paper recently published in the journal Current biologyA team of scientists say they have identified this strange creature, which is actually not a single animal but 1,020 parasitic worms clinging to each other in a tight, bubble-like position. As far as parasitic contests go, this might rank up there with Leucochloridium paradoxum Worms Which turns snails into psychedelic zombies (more on that in a minute).
Minimizo collected one specimen from the animal and packaged it in formaldehyde so researchers could study it. Scientists examined the small sample under a microscope to find that the jellyfish was made of two species of cercariae, which are larval forms of parasitic worms called trematodes. Flukes contain some… The most joyful cycles of life Of any organisms on the planet, they usually have to pass through different hosts to complete their life cycle. But it’s a very wide world, and there’s no guarantee that a vulnerable parasite will encounter both target hosts, so many have developed quite strange strategies to get their attention. For example, pulse Leucochloridium paradoxum The larvae wriggle toward the snail’s eyes, replace them, and begin pulsing to make the snail prey more visible to the host.
Flukes begin their lives as eggs, often released in the feces of birds, mammals, or fish. The egg then hatches into a salami-like hair, and swims through the water to find its first host, perhaps a snail. Once the salami finds the snail, it burrows into the snail’s body and then reproduces itself in the free-swimming cercariae, which are often ejected from the host and swim through the water in search of a secondary, often larger, host, such as a bird, fish, or mammal. The goal of the cercariae is often to be eaten by this third and final host so that it can reproduce sexually within its body and lay fertilized eggs that are then released via feces. Ah, the twisted circle of life!
In the case of the mysterious creature from Okinawa, scientists have discovered that the jellyfish-shaped cluster consists of two species of cercariae: large, tentacle-like “sailors” and small “passengers.” The specimen contained over 1,000 passengers arranged in a hemisphere, with the larger sailors mounted on the flat side, waving their tails like snakes on the head of Medusa. These large sailor tails were wiggling in unison to help the entire worm bubble move. If sailors hit their tails in sync, the point pulses or jumps. If they hit their tails asynchronously, the point flows smoothly. Before it was preserved, the worm colony had a yellowish color inside the tentacle-like sailors, and a brown color inside many, many stirrups.
When the researchers sequenced parts of the worm’s genome, the closest matches were… Pleurches, a genus of trematodes. But the type is unknown.
Are 1020 worms clustered in the approximate shape of a jellyfish a sign eerily reminiscent of Biblical accurate angel? Maybe, but it’s certainly a sign of evolution, and an example of a number of creatures mimicking prey to increase their chances of eating it. The researchers suggest that colonies of swimming worm larvae mimic the movements of small planktonic worms. This act is very popular among other species of trematode larvae, some of which have developed unusually long tails. Another terrifying strategy of fluke caterpillars is called – I don’t know – “Rattenkönig”, which occurs when a group of worms band together by their tails, forming a writhing wheel reminiscent of a rat king. (You can stare in horror at the Rattenkönig bubble worm hereOr you can live the rest of your life in complete peace.)
Joining together in a jellyfish-like bubble certainly helps hundreds of worms swim around. But the researchers suggest that this aggregation may offer other benefits, such as increasing the number of parasites ingested in a single dose and ensuring the worms reach their correct host (small fish would not be able to swallow such a powerful drop). The researchers noted that polymorphism, or multiple forms present for a single species, is rare in parasitic flatworms. So the distinguished sailors and passengers gathered in this jellyfish-like assemblage represent a new instance of such disparate forms in a single fluke.
As the researchers examined the passengers, they found “sophisticated penetration glands” that would allow the larvae to invade their host’s tissues. But the larger sailors had no such hacking devices, making their ultimate fate a mystery. Are these great sailors sacrificing themselves to help transport hundreds of passengers to their final destination? This scenario means that small worms adhere to a strong division of labor, similar to the specialized castes of various insect species. Or do mariners forego lurking in specific host tissues to reproduce and instead mate in a massive gastrointestinal orgy? Orgies can happen anywhere, so why not in the stomach?
We don’t have the answers to these questions now, which begs a bigger question: Do we eventually need them? The sea is full of secrets, and many things are not as they seem. Some of the squirming little creatures are tiny jellyfish, others are layers of annoying parasitic worms united by an overwhelming desire to be eaten and eventually spread. Tag yourself!
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