Toxin-secreting hammerhead flatworms spotted in Westmount

An invasive species increasingly present in North America that secretes a paralyzing toxin has been found in Westmount.

Lisa Osterland, a retired teacher, discovered about 20 hammerhead flatworms (also called bipalium) in her garden.

Earlier this week, she was removing slugs that eat flowers in her garden when she noticed a kind of invertebrate that she had never seen before.

A few days later, she came across a report from CNN that said hammerhead flatworms were now spreading in New York State.

"The shape of the worm was the same as what I had seen [in the garden, so] I knew right away what it was," she told The Canadian Press.

The retiree says she spent a lot of time collecting the worms at night, the time of day when they seem to be more active, and then handed them over to a team of entomologists from Université de Montréal.

In recent years, a few sightings of hammerhead flatworms have been reported in Gatineau and Montreal, but this is the first time so many have been reported in the province.

A paralyzing toxin

The worms spreading is cause for concern because of the paralyzing toxin they secrete. 

Université de Montréal entomologist Étienne Normandin says the tetrodotoxin that hammerhead flatworms produce — also found in pufferfish — is one of the most powerful molecules in the biological world.

If ingested, the toxin first affects the face, tongue and esophagus, a situation requiring immediate medical attention, he said.

LISTEN | Hammerhead flatworms make their way to Montreal:

"If a toddler puts dirt in their mouth and ingests a flatworm or two or more, expect a real risk of harm," he added.

Hammerhead flatworms are also a hazard to birds, dogs, and other critters that frequent gardens.

The presence of a predator like the hammerhead flatworm also threatens soil biodiversity.

Normandin explained that the invasive species has no predators since it is new to the area. By preying on slugs, snails and centipedes — which play an important role in recycling organic materials — the worm can alter ecosystems.

Species from Asia

The invasive worm originated in Asia and was likely transported to North America via cargo ships.

Normandin says the worm probably arrived when plants were imported.

"Often, we find it in well-off neighbourhoods [like Westmount], because in these neighbourhoods, we often have a lot of landscaping, we have exotic species of plants that are beautiful," and that are imported from distant countries, he said.

The hammerhead flatworm was first seen in Montreal in 2018 by a member of the Université de Montréal entomologist team, but it was probably already in neighbourhoods around Mount Royal, according to Normandin.

Climate change could extend worm's survival

According to Environment Canada, invasive alien species can cost the global economy billions of dollars each year by hindering forest productivity, agriculture, fisheries and increasing costs of control measures.

Invasive species pose a new threat to Canada's northern ecosystems as the climate warms and species that usually don't tolerate northern climate conditions expand their ranges, the government agency's website reads. 

"Traditionally, when an invasive species arrives from Asia, the Quebec winter will kill it, [but] now, the average temperatures in winter and summer are higher," Normandin said, explaining that climate change gives a species like the hammerhead flatworm an extra chance to thrive.

The Forests, Wildlife and Parks Ministry did not provide a comment by publication time.