Invertebrates Active day and night

Winged Mapleleaf

Quadrula fragosa

iNaturalist Wikipedia

Meet one of the rarest inhabitants of the Mississippi basin, the Winged Mapleleaf. This ancient bivalve is a living filter, working silently beneath the river's surface to keep our waterways clean.

0 Sightings

0 Habitats

Quick Identification

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Size

Adults typically measure between 5 to 10 cm (2 to 4 inches) in length, featuring a thick and heavy shell.

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Colors

Exterior varies from yellowish-green in juveniles to dark brown or black in adults; interior nacre is pearly white.

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Key Features

Distinctive wing-like ridge on the posterior slope
Surface covered in prominent, bumpy nodules or pustules
Heavy, thick, square-shaped shell
Two distinct ridges separated by a wide, shallow groove

When You’ll See Them

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Activity pattern Active day and night

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Peak hours 24 hours (sedentary)

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Season Year-round

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Diet A suspension feeder that siphons river water to consume phytoplankton (microscopic algae), bacteria, and fine organic detritus.

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Habitat Large, high-quality rivers with moderate currents and stable substrates composed of clean sand, gravel, or cobble.

public Geographic range

Where Does the Winged Mapleleaf Live?

Native to the interior of North America, the Winged Mapleleaf was historically widespread across the Mississippi, Ohio, and Missouri River basins. Today, it is restricted to just a few isolated pockets in the United States, with the most significant remaining population found in the St. Croix River between Minnesota and Wisconsin. It is a rare sight, clinging to survival in high-quality river stretches that have escaped significant pollution and damming.

Basemap © OpenStreetMap contributors

1 Countries

500 km² Range

Critically Endangered Conservation

US United States

Marginal

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iNaturalist / Verified observation data

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Behavior

The Winged Mapleleaf is a sedentary filter feeder that spends most of its long life partially buried in the riverbed. Using its muscular foot to anchor itself against the current, it acts as a natural water purifier. By siphoning water through its body, it filters out microscopic particles, contributing to the overall health and clarity of the river ecosystem.

Perhaps the most fascinating aspect of its behavior is its reproductive cycle. Like many freshwater mussels, it relies on a specific host fish—the Channel Catfish—to complete its development. The female releases larvae (glochidia) that must attach to the gills of the fish, where they hitchhike and grow until they are ready to drop off and begin life on the river floor. This complex interaction means the mussel's survival is intrinsically tied to the presence of healthy fish populations.

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Camera Tips

Capturing the Winged Mapleleaf on camera requires a specialized approach since this species is entirely aquatic. If you are using an underwater trail camera, focus on clear-water stretches of river with stable gravel or sand bottoms. Look for the 'syphons'—small, tube-like openings protruding from the riverbed—which indicate a live mussel is buried just beneath the surface.

For the best results, mount your camera to a weighted plate or a low-profile stake to keep it steady against the river current. Position the lens at a slight downward angle, roughly 12 to 18 inches above the substrate. Lighting is critical underwater; try to position the camera so that natural sunlight illuminates the bed during midday, or use a camera with subtle infrared LEDs for night observations.

Because these mussels are indicators of a healthy ecosystem, capturing them also means capturing the surrounding wildlife. Set your camera to record short video clips (15-30 seconds) to catch the movement of host fish like the Channel Catfish passing by. This provides a fascinating look at the symbiotic relationships required for the mussel to thrive. Remember to check local regulations before placing any equipment in protected riverways.

Similar Species

Species that look similar or are commonly confused with Winged Mapleleaf.

Mapleleaf

The common Mapleleaf lacks the prominent posterior wing and typically has fewer, more organized rows of nodules.

Pimpleback

The Pimpleback is more circular in shape and lacks the distinct square-ish profile and deep groove of the Winged Mapleleaf.

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Frequently Asked Questions

The Winged Mapleleaf is active 24 hours a day. As a filter feeder, it continuously siphons water to eat and breathe, though its biological processes may slow down in very cold winter temperatures.

Because they are a federally protected and highly endangered river species, you cannot attract them to a typical backyard. However, if you live on a large, clean river within their range, protecting your shoreline from erosion and avoiding the use of lawn chemicals helps maintain the water quality they need to survive.

They eat microscopic organic matter, including algae (phytoplankton), bacteria, and tiny bits of decaying plants filtered directly from the river water.

No, they are extremely rare. They are only found in a few high-quality river systems in the U.S. Midwest, far from the typical suburban pond or stream, as they require very specific water flow and purity levels.

The Winged Mapleleaf has a more pronounced 'wing' or ridge on its back and a deeper groove (sulcus) than the common Mapleleaf (Quadrula quadrula). The bumps on the Winged Mapleleaf also tend to be more numerous and extend further across the shell.

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