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The pictured creature, shown at the bottom of a glass, was attached to a friend’s child after he was swimming in the Ottawa River today. It stretches out to roughly an inch in length but in this “resting pose” was around half that length. Below is a shot of the mark left behind:

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It looks like a leech to me, but I thought I’d ask the Internet.

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1 Answer 1


Yes this is a leech. It appears to be a species in the family Glossiphoniidae, or the freshwater jawless leeches. This family of leeches is relatively flattened with a poorly defined anterior sucker.

According to The Canadian Encyclopedia, there are about 45 species of leeches found in or around Canada.

Langer et al. (2018)1 provide a more limited selection of Glossiphoniidae leeches they ascribed to Ontario. Of the ones they list, yours most looks like a specimen from the genus Placobdella.

See, for example, this image of Placobdella phalera from de Carle et al. (2017)2 found in Ontario, Canada:

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Source: Figure 1, de Carle et al. (2017)

1 Langer, S.V., Vezsenyi, K.A., De Carle, D., Beresford, D.V. and Kvist, S., 2017. Leeches (Annelida: Hirudinea) from the far north of Ontario: distribution, diversity, and diagnostics. Canadian Journal of Zoology, 96(2), pp.141-152.

2 de Carle, D., Oceguera-Figueroa, A., Tessler, M., Siddall, M.E. and Kvist, S., 2017. Phylogenetic analysis of Placobdella (Hirudinea: Rhynchobdellida: Glossiphoniidae) with consideration of COI variation. Molecular phylogenetics and evolution, 114, pp.234-248.


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