INVASIVE SPECIES

- by Marlon Madden June 7, 2023

LOCAL SCIENTISTS RAISE ALERT ABOUT PREDATORY FLATWORM

By Marlon Madden

Scientists are reporting the invasion of the predatory New Guinea flatworm in Barbados that is already well established in Christ Church and is spreading to other parts of the island, warning that they may have an impact on soil health and agriculture production.
Lecturer in Biology at the University of the West Indies (UWI), Cave Hill Campus Darren Browne cautioned that the shiny, dark brown/black flatworms could make pets and livestock sick if ingested, and potentially be carriers of a parasite that causes meningitis.
He made the disclosure on Monday night during a public lecture hosted by the Faculty of Science and Technology at the Cave Hill Campus of the University of the West Indies.
Noting that the guinea flatworm was “spreading quickly”, Browne said it was able to withstand temperatures up to about 43 degrees Celsius and could, therefore, have easily been imported into the island on any soil plant material since the treatment on those was about 34 degrees Celsius.
“They produce very quickly so they reach sexual maturity in about 14 days and they produce eggs in cocoons that they bury in soil. They produce about nine offspring per cocoon which doesn’t seem like that many; however, they can produce a new cocoon every ten days. That is sexual reproduction but they can also reproduce asexually and that is common for all land planarians. Any segment of a worm that is damaged can grow into a new worm,” he explained.
Explaining why Barbadians should be concerned about the New Guinea flatworm, Browne said that while they are predators of land snails, slugs and earthworms, and farmers and people with gardens “don’t mind something that controls those, New Guinea flatworms feed on earthworms and this is a major issue”.
“By reducing the population of soil detritivores, they can actually change the soil structure, they can change nutrient availability to plants, they can change the porosity of the soil and make it more likely to flood. This is a problem that we would be very concerned about in Barbados,” he said.
Browne cautioned that the end result “is potentially a reduction in agricultural productivity”.
“They are also toxic if ingested. Most land planarians produce some form of toxin. Pets and livestock are not accustomed to seeing these organisms, so to feed on them they are not necessarily lethal [but] they may induce vomiting in pets and livestock and in human beings as well.
“They also act as hosts of these zoonotic parasites [that can be spread between animals and humans]. We are not sure at the moment that this parasite is actually in Barbados; this is a parasite that can cause meningitis in humans and it can be carried by a number of different things including giant African snails. But we don’t want to have a new vector of this on the island, so if we do find that it is present we now know there are more ways in which people can become infected,” Browne added.
Describing the species as “the vanguard of the new invasion”, the university lecturer said it was first reported in Barbados in October 2020, after about a week of heavy rainfall.
“Someone found these strange – as they called them – black earthworms in their garden. So we did an initial survey of this site as well as the surrounding area and found about 60 individual worms. Whether they were reproducing or becoming damaged, with the damaged parts growing into new worms, we weren’t sure but we suspect they are reproducing now,” he said.
Browne explained that after a few different survey approaches were used, it was found that there were “quite a few worms” at some 11 locations on the island. He said the last update was that there were 23 reported sites.
Most of the flatworms, he said, have been spotted in Christ Church and “a few” from other parishes, including two sightings in St Michael, one in St James, one in St Andrew and one in St Philip.
“We know there are two major hotspots in Christ Church and then these other smaller one or two reports,” said Browne.
The lecturer reported that an initial habitat sustainability model was done to help predict where the flatworms may be able to spread on the island. Based on that study, which primarily examined environmental conditions, “St Thomas and St George may be next on its list”.
The flatworm is native to New Guinea and islands north of Australia and is a predator of snails, slugs, earthworms, millipedes and other soil invertebrates. However, Browne said this predator could easily become an invasive species and wreak havoc.
“What is interesting here is the rate at which this worm has spread. In 2014, it was spotted in Europe for the first time. In 2015, it showed up in Florida and Puerto Rico. In 2020, it was identified in Martinique and Barbados and in 2022, it was identified in Jamaica. So it is spreading throughout the Caribbean now,” he said.
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