Researchers studied the marine flatworm Symsagittifera roscoffensis in petri dishes and found its circular swimming, a type of collective behavior, helps the green algae living within its gut to photosynthesize. In findings published July 25 in Royal Society Open Science, the same team provides proof that these worms behave the same in natural surroundings off the coast of Guernsey.
A.B. Sendova-Franks et al., “Plant–animal worms round themselves up in circular mills on the beach,” Royal Society Open Science, doi:10.1098/rsos.180665, 2018.