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How Do Fingernail Clams Eat?

There are two main groups of freshwater clams and mussels found in North American waters. The larger variety, the Unionidae, resemble the familiar seaside clams and mussels. The smaller variety, the Sphaeriidae, are aptly described as "fingernail clams" for their small size, usually no larger than an adult human's fingernail. Although tiny, fingernail clams live in much the same way as larger species.

How Clams Feed
- Clams and most other molluscs, including oysters and mussels, belong to a group called "filter feeders" by scientists. They make their living by using a muscular tube, called the siphon, to draw water through their digestive tract. The clam's gills do double duty, serving both as the clam's breathing apparatus and a trap for filtering nutrients from the water as it passes through. The clam's food, consisting of plankton and particles of plant debris, are then passed through the intestine, while sand and other indigestible particles are expelled.
Fingernail Clams
- There are about 200 known species of freshwater clams and mussels in North America. Many of those are fingernail clams. Fingernail clams are anatomically similar to larger clam species, native either to fresh or salt water. Like other clams they are bivalves, meaning they have two shells, as opposed to the single shell of a snail or the jointed shell of a crustacean. They live along the bottom of bodies of water, with some species preferring rivers and others inhabiting lakes or ponds.
Freshwater Clams and Biodiversity
- Freshwater clams are a significant factor in North American biodiversity. Where their numbers are high, filter-feeding clams and mussels play a large role in keeping water clear and removing nutrients that might otherwise contribute to algae blooms and other undesirable effects. Larger clams and mussels provide a valuable food source for animals such as otters and raccoons, while the smaller fingernail clams are eaten by smaller predators, including fish and salamanders.
Threats
- Like their saltwater cousins, the filter-feeding habit of freshwater clams makes them highly susceptible to pollutants, which accumulate in their tissues. Because of this, their consumption by humans is not recommended in most areas. Biologists and other scientists pay close attention to clams and mussels as a means of tracking the levels of pollution and contaminants in waterways. Aside from pollution, freshwater clams face two other major threats. One is habitat destruction, as construction and development impinge on wetlands. The other is the arrival of invasive foreign species such as the zebra mussel, which outcompete native species for food and habitat.

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