What do kayakers and river snails have in common?
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Both kayakers and river snails are animals who rely on freshwater. For a kayaker, it's for recreation. But for a snail, it's about livelihood. Freshwater snails live underwater. They feed on algae and other bits of aquatic food. Like kayakers, they depend on certain conditions of temperature, water flow and water quality for their activities.
Many of us have seen a land snail on a sidewalk or plant. On beaches, we have found shells that belong to marine snails. These include periwinkles, whelks and conchs. But freshwater snails are less visible. They also are less understood. Yet, freshwater snails are a really diverse group. There are upwards of 4,000 known species. They live on every continent but Antarctica.
What makes a snail a snail? It's an animal in the class Gastropoda. We think of snails as having shells. But slugs are actually snails as well, technically. What gastropods have in common is a muscular foot. Gastropod means "stomach foot." It extends out from the bottom of their shell with the stomach and other organs coiled above. Most gastropods use the foot to move around. This is whether they are creeping, swimming or burrowing. Slime secreted by special foot glands helps smooth their way forward.
Many human activities affect snails. Humans can pollute or otherwise alter the habitats they live in. Freshwater snails are particularly vulnerable. That's because they live in patchy environments. Imagine the view from above a landscape dotted with ponds, lakes and streams. Snails are not exactly speedy. And if the freshwater they live in becomes uninhabitable, they may not have the ability to move to a new setting.
Damming, mining, draining and the myriad of other changes to freshwater ecosystems have taken a toll on freshwater snails. The impacts show in the dozens of species that have gone extinct. Dozens more are at risk of extinction. While we might wonder about the significance of losing any single species of snail, collectively they sustain food webs in which they play roles as ecosystem engineers. They can break down dead materials, cycle nutrients and maintain water quality.
Zoologist Ellen Strong studies freshwater snails in an effort to understand their biodiversity and ecosystem needs. Learn more about her work on these cryptic animals in the "Smithsonian Science How" webcast. It airs on Thursday, May 11. During How Humans Impact Freshwater Snails (airs at 11 a.m. and 2 p.m. EDT on the Q?rius website), Ellen will take you on a journey to her field sites while answering your questions live. You can also get teaching resources to use with the webcast.
CRITICAL THINKING QUESTION
How can something as large as a kayaker and as small as a snail have anything in common?
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