Just When You Thought It Was Safe to Go Back in the Water: Blood-sucking Snails

It’s okay, unless you’re a fish

Bronwen Scott

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Photo by Nariman Mesharrafa on Unsplash

I was bitten by a snail once. It wasn’t a surprise attack. I had seen a pond snail (Lymnaea stagnalis) eating a dead tadpole and wondered if I could persuade it to do the same to my finger tip.

The snail took to the job enthusiastically, attacking my skin with hundreds of tiny teeth. Within seconds, those teeth had scraped away the outer layer and exposed the painful one beneath. Before it drew too much blood, I put the animal back in the aquarium. Then I went in search of iodine and a dressing.

I did not repeat the experiment.

Many snails are carnivores. Some cone shells (Conidae) are active predators of marine fish, first paralysing prey with venom and then swallowing it whole. Violet snails (Janthina) float on bubble rafts, pushed around by sea breezes that bring them into contact with their food — Portuguese Man-o-War (Physalia), By-the-Wind-Sailors (Velella), and other species that live at the interface between ocean and air.

Land snails are sometimes fearsome predators. No, really. Members of family Rhytididae are almost exclusively carnivorous, as are those of Spiraxidae. American readers might be familiar with the Rosy Wolfsnail (Euglandina rosea, Spiraxidae), which is native to the southern states (and sounds like a nom-de-plume of a romantic suspense author.) This species was taken to Hawaii to eliminate the introduced Giant African Snail (Lissachatina fulica), so destructive of crops and stucco. But Rosy hadn’t read right to the end of the project description. Consequently, a number of native Hawaiian snails have become extinct under the rasping radula, while the African Snail goes about its business. It is a snail eat snail world.

Colubrariidae is a family of marine snails with tall, robust, sometimes heavily sculptured shells with a spire like the crumbling turret of a Gothic mansion. Margin shells (Marginellidae) are also marine. Their shells are smooth and rounded and the pleasing shape and subtle colours make them popular with collectors. Both families contain species that are blood-suckers.

Picture this. It is night on the reef, and a parrotfish dozes among the coral…

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Bronwen Scott

Zoologist, writer, artist, museum fan, enjoying life in the tropical rainforest of Far North Queensland. She/her. Website: bronwenscott.com