"Flatworms can look a bit disturbing, but these species are very small and not dangerous at all. They can be present in high densities at sandy beaches here in the north, such as in Telegrafbukta in Tromsø", says Joel Vikberg Wernström, a PhD Fellow at UiT The Arctic University of Norway.
Flatworms are animals with some traits which seem almost otherworldly. Their mouth is not situated on the head, but in the middle of the body, and many species can regenerate their entire body after having been cut into pieces. While the worms in the sands of Telegrafbukta are free-living, many flatworms are also parasitic.
One of the species found in Telegrafbukta is called Itaspiella helgolandica and was first discovered on the North Sea coast in continental Europe, far south of Tromsø. Later on, it has also been reported from Greenland, Svalbard, the US and Canada.
Since flatworms can appear in high densities and eat other small animals and decaying matter, they likely contribute substantially to nutrient and energy cycles of sandy beaches. They live between the sand grains and act as miniature beach cleaners, which makes them interesting from an ecological standpoint.
The researchers of the UArctic Thematic Network on Arctic Marine Biodiversity have recently published an article about the find of Itaspiella helgolandica in Telegrafbukta in the journal Marine Biodiversity.
"What surprises us the most is that these flatworms have such large distributions despite the fact that they lack a larval stage, and they cannot swim especially well. Since they only live at sandy beaches, they should find it difficult to disperse to new habitats, not to say between continents", says Wernström.
From the perspective of evolution, such a large range in one species of tiny animals seems mysterious - if populations cannot exchange genetic material, one would expect speciation to occur over time. However, Itaspiella and its relatives reproduce using an egg capsule which has a slime stalk that keeps it attached to the substrate. This may be the key to spread to new areas.
Photo: Egg capsule from Notocaryoplana arctica, another species of flatworm found in Telegrafbukta. Note the slime stalk which is used to attach the capsule to substrate, possibly including pieces of floating debris which would permit spreading to new areas.
"We are now trying to find out whether, and how, they disperse on the local and global scales through studying the egg capsules and comparing genetic markers of worms from Greenland, Svalbard and northern Norway", concludes Wernström.
Vikberg Wernström, J., Smith, J. & Altenburger, A. Morphology and phylogeny of Itaspiella helgolandica, an interstitial marine flatworm with circumpolar distribution. Mar. Biodivers. 55, 6 (2025). DOI: https://doi.org/10.1007/s12526-024-01486-w
Main news photo: One of the flatworms in Telegrafbukta, Itaspiella helgolandica, measuring around 0.5 mm in length. These small animals live in their thousands at the sandy beaches which we humans also like to use, but researchers are still not sure of how they manage to disperse across the globe.