Sorry to make you squirm, but this invasive worm is in Newmarket

Paleobiologiest and former ROM curator David Rudkin has twice spotted the hammerhead flatworm -- a non-native predator to soft-bodied invertebrates -- in his Newmarket garden

Newmarkettoday.ca
June 10, 2022
Elizabeth Keith

While there have been no "official" observations of the hammerhead flatworm in Ontario, Newmarket resident David Rudkin has seen the invasive species twice in his garden.

As a paleobiologist and former curator at the Royal Ontario Museum, Rudkin said he knew a fair bit about worms, which is why he realized what he saw was different.

"When I saw these, I recognized them as not being typical earthworms for what we see in this part of the world," he said.

Unlike a segmented earthworm, which is more common here, these flatworms have a long unsegmented body and this particular kind has a little hammer-shaped head.

Rudkin's first sighting of this creature was on Sept. 23, 2019 under a flat rock in his garden. The second was exactly two years later on Sept. 23, 2021 when he saw another hammerhead worm under a clay dish that is a bird bath in his garden.

He recorded both sightings on iNaturalist, a community science app were people can make observations of plants or animals they encounter. Rudkin is the only one who has reported seeing hammerhead worms in Newmarket on the app, but said that doesn't mean there aren't more in town.

"I suspect that most people simply wouldn't recognize these little things as being different than any other worm that they were digging up in their in their gardens, so they're probably here in greater numbers, but unobserved," he said.

There has been only one confirmed sighting of the flatworm in Canada. The observation was in 2019 in Quebec and was written about by Jean-Lou Justine, Thomas Thery, Delphine Gey, and Leigh Winsor for the scientific journal Zootaxa.

"When we talk about confirmed sightings, we're kind of usually referring to confirmed in the scientific kind of academic sense. In Canada, there is that one observation there. There are a number of other observations in Canada already, through more sort of naturalist kinds of platforms and community science platforms," said Michael McTavish, a fellow with the S.M. Smith Forest Health Lab.

He said iNaturalist, the app Rudkin used to report his sightings, is a very popular platform for these observations with around 40 reports of flatworms going back to 2016.

McTavish said the worms are a predator to soft-bodied invertebrates, including earthworms. He said the term invasive species is used for two reasons: they are not native to the area and they have a negative impact ecologically.

"The worms that we're talking about check both of those boxes in that they are non-native. They're not from North America. They're primarily overseas, I believe Asian in origin for the most part, depends on the species," he said. "And then they will be invasive in that we're concerned about the impact that they can have as invertebrate predators."

McTavish said they likely were transported to the area through horticultural materials and pose a risk to earthworms already in Ontario.

However, he said people don't need to take any immediate action if they see these worms in their gardens. The best thing to do at this time would be documenting the observation.

"Early detection and monitoring is really crucial for establishing where they're spreading from these kind of early days and that invasion," he said.

He said you can report it to the Invasive Species Centre, which has an online reporting tool, or on a community science app like iNaturalist, the one Rudkin used.

Other than photographing and sharing his sighting, all Rudkin said he did was a bit of research on the worms and just let them be. He hasn't made an observation since last fall but joked he would check again this year on Sept. 23.