Newly-Discovered Branching Worm Named After Godzilla's Legendary Nemesis

A rare, new species of branching sea worm with "regenerative butts" were recently discovered living inside sea sponges in Japan that biologists named after a monster notable for its three heads, and Godzilla's monstrous nemesis, King Ghidorah.

Unlike their namesake, who has three heads and two tails, the new worms called Ramisyllis kingghidorahi only have one head but do have multiple posterior branches or "regenerative rear ends" that detach and swim off during reproduction.

"King Ghidorah is a branching fictional animal that can regenerate its lost ends. So we thought this was an appropriate name for the new species of branching worm," lead author Maria Teresa Aguado, an evolutionary biologist specializing in marine invertebrates at the University of Göttingen in Germany, said in a statement.

According to LiveScience, the R. kingghidorahi is the third species of branching sea worm ever discovered.

A "higher diversity of tree-like animals"

There are two other species of these bizarre branching worms that have been previously discovered in the Philippines and Northern Australia. The first discovery (Syllis ramosa) had "remarkably branched Syllid", while the second (Ramisyllis multicaudata) also had "randomly branching asymmetrical body" and lived inside the labyrinthine canals of sea sponges.

"We were astonished to find another of these bizarre creatures with only one head and a body formed from multiple branching," Aguado's statement in ArsTechnica. "The first worm was thought to be unique. This discovery reveals a higher diversity of these tree-like animals than anyone expected."

The authors' investigation published in SpringerLink revealed that the Ramisyllis multicaudata and Ramisyllis kingghidorahi share a common evolutionary ancestor, although there are still some genetic divergences, particularly regarding the shape of certain body segments.

"This study suggests a much higher diversity of branching syllids than currently known," the authors wrote.

Mysterious history of over a hundred years

The authors suggest that the new species of branching syllids may have adapted the intricate labyrinth of the sponge canal system, "with the ability to produce new fully developed segments allowing the worm to explore the canals."

The researchers aim to explore the unique, mysterious relationship between the worms and their sponge hosts.

"Scientists don't yet understand the nature of the relationship between the branching worm and its host sponge: is it a symbiotic relationship where both creatures somehow benefit? And how do the worms manage to feed to maintain their huge bodies having just one tiny mouth in their single head?"

These mysteries remain despite these worms' existence being known for over a hundred years. The researchers hypothesized that the possible explanations for their feeding behavior is related to its highly ciliated wall of the digestive tubes (especially at the distal branches and anus), and the evolution of branching body patterns as the result of an adaptation to the host sponge labyrinthic canal system.

In short, their capacity to produce new posterior segments throughout their whole lives, as well as their regeneration during reproduction, are products of the evolution of a branching body.