Freshwater mussels, unassuming bivalves found in rivers, lakes, and streams, play a unique role in aquatic environments. These fascinating creatures are often partially buried in the substrate, where they engage in a specialized feeding method. Their ability to draw in and process large volumes of water is central to their survival and influences the health of their surrounding habitat. This feeding strategy allows them to obtain sustenance while performing a significant ecological function.
What Freshwater Mussels Eat
Freshwater mussels primarily consume microscopic particles suspended in the water column. Their diet includes tiny organisms such as phytoplankton and zooplankton. They also filter out detritus, consisting of decaying organic matter, along with bacteria and other microorganisms. Specific examples of their microscopic food sources include diatoms and various forms of algae.
The Filter-Feeding Process
Freshwater mussels are adapted for filter-feeding, a process that begins with drawing water into their bodies. They use an incurrent siphon to pull water, along with suspended particles and oxygen, into their mantle cavity. Inside the mussel, the water flows over specialized structures called gills. These gills are covered with microscopic hair-like structures called cilia, which beat rhythmically to create water currents and trap food particles.
Particles become entangled in a sticky mucus net on the gills. This mucus-bound material is then transported along grooves on the gills towards the mussel’s mouth. Any inedible or excess particles are bundled into what are known as pseudofeces, which are then expelled from the mussel’s body, often via the excurrent siphon. The filtered water, now free of many suspended particles, is expelled through an excurrent siphon, completing the filtration cycle.
Why Their Diet Matters to Ecosystems
The feeding habits of freshwater mussels have significant effects on their aquatic ecosystems. Mussels act as natural water filters, improving water quality by removing suspended particles, including algae and sediment. A single freshwater mussel can filter a substantial volume of water, ranging from 8 to 20 gallons per day, depending on the species and conditions. This filtration ability helps to clarify murky water, which allows more light to penetrate and supports the growth of aquatic plants.
Beyond particulate removal, mussels also contribute to nutrient cycling within their habitats. They process organic matter and convert nutrients into their own tissues, while also releasing dissolved nutrients through excretion. These excreted nutrients can become available to other aquatic organisms, influencing the broader food web. By removing excess nutrients and pollutants, mussels help maintain healthier conditions for fish and other aquatic life. Their presence can lead to enhanced biodiversity in the water column.