Freshwater Snails


In July 2022, I saw several thousand tiny, dark, rounded organisms in the bottom of a channelized arroyo in Albuquerque. They were in shallow water (roughly half an inch deep), moving slowly along the bottom. When I looked more closely, they turned out to be freshwater snails. Some of the shells were coated with algae—whether deliberately or accidentally, I don't know.



Before that morning, the only snails I'd seen in New Mexico (including in my yard) were land snails, with shells that looked a lot like the ones used to serve escargots.  The shells I was looking at that morning were pointed spirals. Thanks to a 1987 monograph by Dwight Taylor, I now know that New Mexico's rivers are home to multiple species of spiral-shelled freshwater snails. I can understand why I never saw them before; in New Mexico's large permanent streams, the water tends to be opaque with suspended clay and silt. In the channelized arroyo, the thin sheet of water the snails were in happened to be clear.