Flatworm Rhynchodemus sylvaticus (Jon Mortin)


Flatworms belong to the Phylum Platyhelminthes which includes both free-living flatworms and parasitic worms (Cestodes and Trematodes). Flatworms are regarded as primitive animals as they lack a coelom or body cavity unlike most other invertebrate groups. They are also unsegmented unlike annelid worms (such as earthworms) which are segmented.

About flatworms

Flatworms have a flattened shape to help with the diffusion of oxygen and nutrients as they lack a proper circulatory system. They include aquatic species (found in rivers and lakes) as well as some which have evolved to live in moist terrestrial habitats (including gardens).

Flatworms in the High Peak

Worldwide there are over 4000 species of flatworm, but so far only 5 species have been found in the High Peak. Four species have been found in ponds and rivers (Dugesia polychroa. Denrocoelum lacteum, Crenobia alpina and Polycelis nigra) and one species (Rhynchodemus sylvaticus) in a Buxton garden. Some large invasive flatworms from Australia and New Zealand have reached the UK from imported plants and may turn up in gardens.

Flatworm Denrocoelum lacteum (Jon Mortin)
Flatworm Crenobia alpina (Jon Mortin)

There are at least five native species of Land flatworms in the UK, but more than ten non-native species. Non-native land flatworms are typically accidentally introduced in imported pot plants and new non-natives continue to be discovered in the UK. Once introduced they can reproduce rapidly, are difficult to eradicate and pose a risk to native invertebrates such as earthworms by feeding on them. 

Buglife have a survey on their website to identify non-native species, and have a short guide to non-native flatworms which is useful.

Text by on flatworms by Jon Mortin

Takes you to the up-to-date list and photo galleries of all flatworm observations within the High Peak area, as recorded on iNaturalist

Takes you to the up-to-date list and photo galleries of all flatworm observations within the ‘Buxton polygon’ area, as recorded on iNaturalist and collected by the Buxton Biodiversity Recording Group project

Identifying flatworms

Reference titles and details welcomed





Information and guidance

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