These sea anemones have a diverse diet. And they eat ants
Study describes intestinal contents of giant feathery anemones off the coast of Washington state
BUFFALO, NY – The giant feathery anemone is an animal, but it looks a bit like an underwater cauliflower. Its body consists of a rod-like column that attaches to rocks and other surfaces on one end and a crown of tentacles on the other.
Anemones use these probes to collect and stuff food into their mouths, and a new study provides in-depth insight into the rich diversity of prey anemones catch. This includes a surprising menu item: ants, especially the field ants with pale legs, Lasius pallitarsis. And the occasional spider.
The research was published on June 15 in the journal Environmental DNA. The study focused on the giant feathery anemones, known to scientists as the Metridium farcimen, which were attached to the sides and undersides of floating docks in the San Juan Archipelago area of northwestern Washington state.
The team used a method called DNA metabarcoding to identify the intestinal contents of a dozen giant feathery anemones. The species’ diet was rich in arthropods, especially crabs (probably larvae, according to the researchers), and also included barnacles (larvae or molts), copepods, and insects.
“We’ve significantly expanded the list of things we know they eat. They eat whatever they can catch, whatever isn’t too big or too small, whatever can’t swim, ”says lead author Christopher Wells, PhD, postdoctoral researcher at the University of Buffalo Department of Geology. “One of the more surprising results is that in addition to all the usual suspects you might find in marine plankton, we also found that part of the diet, around 10% at the time of the study , was made up of ants, which are not sailors.
Digging into the natural history of the pale-legged field ant, the researchers offered a possible explanation for how these ants became part of the marine food chain.
“It’s timed with the reproductive part of the lifespan,” Wells says, noting that the study was conducted during the month of August, when ants have mating flights. “They produce winged queens and drones, which mate and form new colonies. They don’t fly very well and the wind pushes them, potentially in the water.
The team’s results indicate that the giant feathery anemones also occasionally eat the hapless spider, as well as a few insects in addition to the ants that can wander too close to the water’s edge and drown.
The study was a collaboration between Wells; Gustav Paulay, PhD, at the Florida Museum of Natural History; Bryan Nguyen, PhD, at George Washington University; and Matthieu Leray, PhD, at the Smithsonian Tropical Research Institute. Wells, now in the geology department at UB College of Arts and Sciences, conducted the research at Friday Harbor Laboratories while completing a doctorate at the University of Washington.
By extracting genetic material from a mixture of partially digested foods, the researchers were able to work backwards, comparing their results to information stored in databases on the DNA of various organisms.
“Part of our research used this method, DNA barcoding, and compared it to the traditional techniques of washing or cutting an anemone and then identifying what you can see. The problem is, when you do that, you can’t identify everything, ”says Wells. “You might say, ‘Looks like it’s a copepod antenna,’ but you can’t tell which species it is. With DNA barcoding, you can identify the species’ antennae. We were able to identify much more diversity using meta bar coding. “
Knowing what an animal eats is essential for understanding the functioning of marine communities.
“When a community of plankton floats above a bed of anemones, the plankton is filtered by millions of tentacles that grip it,” says Wells. “This can dramatically change the makeup of the plankton community, which is the food for many economically important animals such as bivalves and fish.”
The anemones found in close proximity to each other had varied diets, but “I don’t think that’s because they choose different things to eat,” Wells says. “They eat what they can, and what they get is very uneven, depending on what’s there.”
While researchers have been able to identify many species that the giant plumose anemone feeds on, Paulay, Curator of Invertebrate Zoology at the Florida Museum of Natural History, noted that they were unable to match a substantial portion of the DNA sequences with known organisms, highlighting how much remains to be discovered in the oceans.
The research was funded by the Robert T. Paine Experimental and Field Ecology Award; Friday Harbor Laboratories and Marine Sciences Endowment Fund; Patricia L. Dudley Endowment Fund for Friday Harbor Laboratories; Richard and Megumi Strathmann scholarship; and Kenneth P. Sebens Endowed Student Support Fund.