A Strange Worm that Acts Like a Plant

Is it an animal? Is it a plant? The “mint sauce worm” (Sysagittifera roscoffensis) is a plant-animal hybrid. It is nicknamed because of its bright green appearance. However, the worm is clear but the algae that lives within it is green. Recent studies have uncovered the worms' mystery.

The worm has all of the characteristics of an animal ... except for the fact that it's “solar-powered.” It uses photosynthesis to get energy from the sun, surviving on nutrients produced by the algae in its gut.

Mint sauce worms are more unique than just in their hybrid nature. Researchers at the University of Bristol have recently released a study of their social behavior. The worms interact with one another to coordinate movements. They collect in groups to produce a super-organism.

The worms, 3mm long marine acoel flat worms, work with one another to begin swimming in small, polarized groups. As densities increase, they form “flotillas” that turn into “circular mills.” Together, they form biofilms or mats, resembling algae. Unlike algae, they can cling to areas where normal seaweed is unable to anchor and gather. The formation provides security in numbers.

Found on select sandy beaches in shallow water on the Atlantic coasts of Wales and the UK’s Channel Islands, the worms gather in mats when the tide is out, actively bathing in the sun. When the water rolls in, they burrow beneath the sand to sleep.

Researchers used computer models to compare these unique worms to other species of worms and learned how their socialization occurs.

Professor Nigel Franks in the School of Biological Sciences at the University of Bristol sums up:

Our study suggests this remarkable organism also seems to be an ideal model for understanding how individual behaviours can lead, through collective movement, to social assemblages.”

Thus, this worm is not related to mint or used as a sauce for lamb as its name suggests.