They discover the identity of a strange sea creature found in Japan after 5 years of studies

The Japanese photographer Ryo Minemizu, specialized in small marine species, captured in April 2018, off the coast of Cape Kiyan, in Okinawa (Japan), images of an organism that he had never seen before and, using social networks on the internet, He asked biologists, naturalists and the general public for help in identifying them.

Oliver Thansan
Oliver Thansan
04 October 2023 Wednesday 10:27
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They discover the identity of a strange sea creature found in Japan after 5 years of studies

The Japanese photographer Ryo Minemizu, specialized in small marine species, captured in April 2018, off the coast of Cape Kiyan, in Okinawa (Japan), images of an organism that he had never seen before and, using social networks on the internet, He asked biologists, naturalists and the general public for help in identifying them. No one was able to give reference to this organic mass that moved in the water, about 15 meters deep, in a similar way to a starfish or a jellyfish but with much greater speed.

After a long work of analyzing the few samples collected and studying its parts, an international team of zoologists and specialists in parasitic worms has identified the strange sea creature from Okinawa. The results of this work have now been published in the journal Current Biology.

Ryo Minemizu not only captured the images of the unknown organism but, upon realizing that no one knew about it, he returned to the waters of Kiyan and caught some specimens, the size of a ladybug, and made them available to the experts.

The results now known indicate that it is not one but two creatures strongly attached to each other that move, live and feed together. "The enigmatic swimming aggregations found in the plankton near the island of Okinawa appear to be colonies of the larval stages of Digenea, cercariae," the authors of the study indicate in their article. The digeneans or digenetics are a subclass of flatworms of the class of trematodes, parasitic worms generally provided with suction cups. The name 'cercariae' indicates the larval form in this class of trematode or fluke parasites.

The results of this work indicate that the double organism observed "probably represents a case of prey mimicry, which in this case aims to attract the host and facilitate transmission." "The type of locomotion of the cercariae aggregate seems to copy the movements of small plankton polychaetes, which undulate their bodies with high frequency while swimming," indicate the authors of the study.

"The peculiar characteristic of the discovered aggregation is the polymorphism of the cercariae it contains. It would therefore be two forms of cercariae, to which the names 'sailors' and 'passengers' are assigned (due to the function they show), which They belong to the same species according to our molecular data, but differ in structure, size and behavior.

The passengers were much smaller than the sailors and the two hugged each other tightly, forming a flat-topped hemisphere. They were pressed together with the head pointing towards the inside of the sphere, leaving the tail exposed and forming the outside of the hemisphere. The sailors grabbed onto the tails of the passengers with their own tails and stretched their bodies in the water, resembling the appendages of the sphere.

A more detailed study of the group of two creatures showed that the sailors used their bodies as appendages, swinging them like cilia on paramecia. And like cilia, sailors moved their bodies in unison as a means of moving the combined mass in the water.

The researchers found that this type of swimming was typically initiated by only one member of the group; Their actions were imitated by those nearby until everyone waved, pushing the group through the water. In doing so, the collectivized group could make sudden movements, jumping from one point to another, or it could move steadily. The researchers suggest that the two creatures have formed a colonial organism that adapts to the needs of both groups.