Large Sea Anemone Additionally Eats Ants, Spiders: How Did These Bugs Attain the Sea?

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Sea anemones are soft underwater predators famous for their bright colors and tentacles that look like flowers. They also eat almost anything they can catch with their mouths. However, a recent analysis of the intestinal contents of a giant plumose anemone reveals a surprising portion of its diet that has never been recorded before.

The study “DNA metabarcoding” published in the journal Environmental DNA offers insights into the diverse diets of a dominant suspension eater, the giant plumose anemone Metridium farcimen.

(Photo: Wikimedia Commons)
Several giant plumose anemones (Metridium senile) found a seat on hard ground material in the central Puget Sound. This filter-feeding anemone is one of the many resident invertebrates better protected by the EPA’s Puget Sound cleanup.

Giant sea anemone also eats insects

The study focused on the giant feather anemone, Metridium farcimen, found on the sides and undersides of floating docks in the San Juan Archipelago in northwestern Washington DC

Science Daily reported that researchers used DNA metabarcoding to identify the intestinal contents of the giant sea anemone, and found that it consisted primarily of anthropods like crabs, but also barnacles, copepods, and insects.

The study’s first author, Dr. Christopher Wells, a postdoctoral fellow from the University of Buffalo Department of Geology, said the giant sea anemone ate everything it can catch. But the surprising results showed that not only does the anemone eat marine plankton, but about 10% of its diet consists of ants that are not sea creatures.

The giant plum anemone looks a bit like a cauliflower, with its stem-like column attached to rocks and other surfaces at or at the end, and a tentacle crown at the other end. They use their antennae to collect and push food into their mouths, which apparently includes non-marine anils, such as ants and the occasional spider.

“DNA metabarcoding lets you identify the antennae of a species. We were able to identify a lot more diversity with metabarcoding,” Wells said, as quoted by Science Daily.

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How could the giant plumose anemone have eaten ants and spiders?

Researchers are digging deeper into the natural history of the insects found in the bowels of the giant plum anemone, according to the Florida Museum press release. They found a plausible explanation for how these ants became part of the marine food chain.

Wells said these pale-legged field ants spent most of their time underground building and improving their colony. In late summer, however, the queen and male ants, equipped with wings from multiple colonies, fly and gather in dense flocks to mate, triggered by the warm temperatures and fine weather.

Unfortunately, these insects were not strong fliers as they were easily swept away by the wind and far off course, sometimes making them into the sea. As much as they are not good fliers, ants are also not good swimmers and drown and are eaten by marine life, including sea anemones.

The results of the study suggest that the giant feather anemone may occasionally eat spiders and some other insect species alongside ants that migrate closer to the water’s edge and drown.

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For more news and information on sea anemones, check out the Science Times.