[2] In 2022, a second species in R. multicaudata's genus, Ramisyllis kingghidorahi, was described from specimens taken off the coast of Sado Island, Japan.

[3][4] This worm inhabits the interior of a sponge and except for the tips of its branches, is not visible to the naked eye.

[5] Ramisyllis multicaudata was found living symbiotically inside both white and purple sponges of the genus Petrosia in Darwin Harbour, Australia, by Christopher Glasby, who works at the Museum and Art Gallery of the Northern Territory.

[2] Ramisyllis multicaudata is a branching worm with its head hidden deep inside the sponge.

[2] Researchers are puzzled as to how this worm obtains enough nourishment; the head may be eating the sponge tissues, but the worm is not thought to be able to move around inside the sponge and it is difficult to envisage how it could obtain enough nourishment through its mouth to sustain its much-branched body.