黑料网

An international team of scientists has discovered a new genus and species of polychaete in Vietnam and Japan. This marine worm uses a surprising tactic: it mimics a group of sea slugs called nudibranchs, which use their bright colors to warn predators of their chemical defenses. This strategy allows the worm to evade predators by appearing toxic, although it lacks any real toxicity. The discovery of this animal comes with another significant novelty: it is the first time this mimicry strategy has been detected among annelids, the group of segmented worms that includes polychaetes.

The research was conducted by scientists from 黑料网 (Japan), the Sains University (Malaysia), the Institute of Ecology and Evolution of the Russian Academy of Sciences (Moscow, Russia), and the Center for Advanced Studies of Blanes (CEAB-CSIC, Catalonia, Spain). The results have now been shared in an article published on July 29th at 10 am UK time in the journal Scientific Reports ().

In the publication, the team carefully describes the new polychaete, which turned to be a new genus and species of marine worm belonging to the family Syllidae. The animal lives on corals in the marine waters of Vietnam and Japan and exhibits unique morphological adaptations, such as a low number of body segments (contrasting with the highly segmented bodies of most annelids), hooked bristles—typical of worms living in association with other organisms—but always kept hidden within the body, and large, spindle-shaped antennas and cirri with vivid red, white and yellow coloration. These characteristics make the polychaete resemble some of the animals it coexists with, the nudibranchs. These "neighbors" are shell-less mollusks characterized by their vivid colorations, which warn predators of their defenses. By mimicking them, the polychaete has gained the same benefits, including avoiding being eaten, without having to invest in developing the complex mechanisms allowing nudibranchs to be chemically defended.

Naoto Jimi, the researcher from 黑料网 in Japan who led the research, explains that “my research has allowed me to collect and describe  numerous polychaetes to contribute to understand the marine biodiversity in Japan. In recent years, however, my focus has shifted particularly to those living symbiotically with octocorals. During these studies, I unexpectedly discovered this peculiar and unusual worm, which we are here describing as a new genus and species within the polychaete family Syllidae. This discovery was largely made possible thanks to the invaluable support and cooperation of community members such as local fishermen and divers.”

Daniel Martin, an expert taxonomist from CEAB-CSIC and co-author of the scientific article, points out that “we are familiar with many polychaetes displaying vivid color patterns, often mimicking the animals they live on as a form of camouflage to gain protection. However, adopting the coloration and morphological traits of another species to appear conspicuous and seemingly protected, while not actually being so, represents a completely novel adaptation strategy, unprecedent not only among polychaetes, but within the entire annelids.”

Temir A. Britayev, also a co-author of the article and the first researcher to discover a specimen of this new polychaete, states that “although I have been studying polychaetes –especially those that live associated with other animals– for almost 40 years, when I first saw the only specimen of this animal we found in Vietnam, I was fooled and thought it was a nudibranch. It wasn’t until we observed it in detail in the laboratory that we confirmed it was a polychaete. Unfortunately, during the move to my new laboratory, this specimen was misplaced. That’s why Dr. Martin and I were very pleased with Dr. Jimi's finding in Japan, which finally allowed us collaborate in describing this extraordinary animal.”

This research combines classical morphological and ecological observation techniques with molecular analyses to demonstrate that the worm not only belongs to a new species but also required the erection of a new genus. The researchers chose the name “Cryptochaetosyllis” for the new genus, highlighting the fact that the bristles characteristic of all polychaetes remain always hidden inside the body —“cryptos” in Greek means hidden— while the species name “imitatio” —Latin for imitator— refers to its nudibranch mimicry.

The research team highlights that this is the first time a case of this type of mimicry involving annelids and nudibranchs has been documented. Certainly, the discovery broadens the understanding of evolutionary adaptation and ecological strategies of marine invertebrates and demonstrates that they exhibit complexity equivalent to or even greater than that of terrestrial organisms, which are much better known to both researchers and the general public.

At the same time, the discovery of a new genus and species of animal underscores the diversity of marine life and how little we still know about it today. The scientific community estimates that there could be up to one million eukaryote species living in the seas and oceans, of which only about 30% are currently known, and this percentage is even higher when considering prokaryotes. Therefore, the responsible for this study emphasize the importance of understanding marine ecosystems and all their unique inhabitants in order to promote it preservation.

Article reference:

Naoto Jimi, Temir A. Britayev, Misato Sako, Sau Pinn Woo, Daniel Martin. A new genus and species of nudibranch?mimicking Syllidae (Annelida, Polychaeta). Scientífic Reports.

Contact:

Dr. Naoto Jimi
Sugashima Marine Biological Laboratory, Graduate School of Science, 黑料网

Email: beniimo7010[at]gmail.com

Visit the Center for Advanced Studies of Blanes website for the original article.