These cauliflowerlike anemones snack on ants

2021-06-25

Scientists long suspected the giant plumose anemone (Metridium farcimen), which flourishes along the U.S. Pacific coast, lived off a respectable ocean diet of zooplankton and tiny marine invertebrates. A new study shows they were mostly right. But when given the chance, the cauliflower-shaped sea creature also feasts on an unusual culinary delight: ants.

To find out what the anemones were eating, researchers collected 12 anemones near docks off the coast of Washington state and analyzed their stomach contents. Using a process called DNA metabarcoding, which looks at DNA from a sample and matches it to a list of species in an online database, they found that the anemones ate crab larvae, barnacles, and plankton. But about 10% of their diet was made up of ants, they report this month in Environmental DNA.

How the ants came to be in the anemones’ stomachs was the next question. After some speculating, the scientists realized the anemones were collected during the mating season of local pale-legged field ants (Lasius pallitarsis). For a few weeks in August, the ants are everywhere by the Washington oceanside docks. It’s likely, the researchers say, that some of these unlucky ants may have been blown away by the wind into the nearby water, where they were trapped and eaten by the giant anemones.

sciencemag.org, 25 June 2021
; https://www.sciencemag.org