S.ea anemones are soft underwater predators known for their bright colors, the flower-like arrangement of the tentacles, and a tendency to eat almost anything they can catch and fit in their mouths. In accordance with this last characteristic, researchers examined the intestinal contents of the giant plumose anemone, Metridium farcimen, have added a surprising food to their menu: ants.
The study marks the first time DNA sequencing has been used to analyze the diet of sea anemones. By extracting genetic material from a mushy mixture of partially digested food, the researchers were able to work backwards and compare their results with DNA from organisms from the tree of life stored in online repositories.
In the past, the most common way to determine what marine animals ate in the wild was to preserve and dissect them, and then look at the remains of their last meal. This method was tedious and unreliable because many of the identifying features of plants and prey had been etched away by digestive juices.
However, knowing what an animal eats is essential in trying to understand how marine communities work. And on the rocky west coast of North America, from the glaciated bays of Alaska to the warm waters of the Baja Peninsula and central Mexico, this is especially true for anemones.
“Anemones are one of the most abundant animals in these ecosystems and they affect the food webs around them,” said Gustav Paulay, curator of invertebrate zoology at the Florida Museum of Natural History and author of the study.
Anemones are related to corals and jellyfish, and often live in dense communities of organisms, where they soar above their competition on hanging stems anchored to ledges or coral reefs. Unlike their jellyfish cousins, anemones stay in a place for most of their lives waiting for food to scatter across their path. With concentric rings of sticky tentacles wrapped in a fine net of poisoned arrows, they harpoon and reel in worms, snails and even fish.
“These anemones are the top floor, including hundreds of species,” Paulay said. “They affect how the water flows around them and how it reaches the lower levels where smaller things live.”
While some of the larger species consume fish, crabs, and jellyfish, others, like the giant feather anemone in this study, feed on plankton, a collective term for almost any small organism that is swept away by ocean currents. Oceans are teeming with microscopic plankton, many of them small crustaceans – krill, copepods, and the developing larvae of crabs, barnacles, and shrimp.
“When a community of plankton swims over an anemone bed, the plankton is filtered by millions of prey tentacles,” said Christopher Wells, postdoctoral fellow at the University at Buffalo and lead author of the study. “This can drastically change the composition of the plankton community, which is the food for many economically important animals such as mussels and fish.”
However, organisms living on land are noticeably absent from this diverse underwater ecosystem.
Hence, it took the researchers by surprise when their results showed that 10% of the food eaten by giant feather anemones was ants, especially the pale-legged field ant. Lasius pallitarsis, often along the coasts of the Pacific Northwest.
By studying the natural history of this species, the researchers found a plausible explanation for how these ants became part of the marine food chain.
“Pale-legged field ants spend most of their time underground working to improve their colony,” Wells said.
But in late summer, queens and male drones from several different colonies, equipped with wings, soar into the sky due to the warm temperatures and beautiful weather, and gather in dense swarms to mate.
“Unfortunately, they’re not strong fliers,” Wells said. “Wind can take you a long way off course, sometimes into the sea. Since they are not good swimmers, they drown and are eaten, sometimes by anemones. “
The team’s results suggest that giant feather anemones also occasionally eat unfortunate spiders, along with some insects in addition to ants that wander too close to the water’s edge and drown.
The study was first conceived during a marine biodiversity methodology course taught at Friday Harbor Laboratories by Paulay and study co-author Matthieu Leray, a postdoctoral fellow at the Smithsonian Tropical Research Institute, and is part of a larger effort by scientists studying DNA Use sequencing to document the diversity of microscopic organisms that live in ocean environments.
While the researchers were able to identify many of the species hunted by the giant feather anemone, Paulay found that they were unable to match any significant part of the DNA sequences with known organisms, underscoring how much remains to be discovered in the depths of the oceans.
“This whole approach is incredibly powerful, but it depends on knowing what the DNA sequences belong to. We’re really behind in the marine world. “
The researchers published their results in Environmental DNA.
Bryan Nguyen of George Washington University also co-authored the study.
Research was funded by the Robert T. Paine Experimental and Field Ecology Award Fellowship, the Friday Harbor Laboratories Research Fellowship Endowment, the Patricia L. Dudley Endowment for Friday Harbor Laboratories, the Richard and Megumi Strathmann Fellowship, and the Kenneth P. Sebens Endowment Fund for Student Support and the Marine Science Fund of Friday Harbor Laboratories.
Photo of Metridium farcimen Neil McDaniel’s Colony.
For more information on the study, visit the University at Buffalo website.
Author: Jerald Pinson, [email protected], 352-294-0452