Symsagittifera roscoffensis is commonly known as the ‘mint-sauce worm’ due to its bright-green colour, and is found in shallow waters on sheltered sand beaches at certain sites on the Atlantic Coast, including the coasts of Wales and the Channel Islands.
The 3mm-long worms sunbathe on beaches when the tide is out and bury themselves in the sand as the sea returns.
Now a new study by scientists from the University of Bristol, UK, led by Professor Nigel Franks from the School of Biological Sciences at the University of Bristol shows that with increasing density the mint-sauce worms form small flotillas, and then circular mills.
The scientists believe that these interactions eventually lead to mat-like biofilms observed on sandy beaches, and may help the worms to achieve safety in numbers and the right conditions for their unusual way of life.
The worms also offer some insights into how inidviduals collect into groups and eventually a social movement. S. roscoffensis is also an ideal model for understanding how individual behaviours can lead, through collective movement, to social assemblages, according to Franks.