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Hammerhead worms (Bipalium adventitium) Along Hardwood Ridge Trail in Oglebay Park

By Jake Francis, Director of Environmental Education – Recently, while catching my wits on the forest floor after a fall, I noticed an interesting invertebrate moving through the decaying leaves. This organism is closely related to the aquatic planaria that many of our Nature Day Campers and School Groups would recognize by its ‘crossed eyes’ and it ability to regenerate from both ends if cut in half. This turbellarian, known commonly as the hammerhead worm, is in the same order (2 taxanomic levels higher than genus) as the common freshwater planarian in our streams, and shares its ability to regenerate after an injury.

The hammerhead worm (Bipalium adventitium) preys primarily on earthworms,which they locate using chemical sensors along the front of their enlarged head. To eat the worms they exude their pharynx (located in the middle of its body), digests the worm, then absorb the nutritious liquid. Here is a link to a hammerhead worm digesting an earthworm showing the pharynx (large white appendage), but be warned the image of digestion is not for the faint of heart! 

This species of flatworm is introduced from Asia, and some scientists believe they pose a threat to north american earthworm populations. For more reading on this interesting beast check out some scientific articles at:

Feeding Behavior of a Terrestrial Turbellarian Bipalium adventitium

Reproductive ecology and evolution in the invasive terrestrial planarian Bipalium adventitium across North America

Observations on Feeding Behavior by the Terrestrial Flatworm Bipalium adventitium (Platyhelminthes: Tricladida: Terricola) from Illinois

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