Flatworms
Order: Polycladida

Appearance

Two species of flatworms can be found in the Chesapeake Bay:

• The oyster flatworm, Stylochus ellipticus
• The slender flatworm, Euplana gracilis

Flatworms have flat, symmetrical, leaf-shaped bodies that grow to a size smaller than a quarter. The oyster flatworm is cream-colored with short tentacles on its sides and has eyespots in two rows along its head. The slender flatworm is yellowish-gray, has a row of eyespots along the front of its body and does not have tentacles.

Feeding

Flatworms are major predators of barnacles, bryozoans and oyster spat. They hunt by waiting for its prey to open its valves to feed. Then the flatworm inserts its mouth into the open valves to feed on its prey’s interior parts.

Reproduction and Life Cycle

The life cycle of the flatworm is not well known. Oyster flatworms have both male and female reproductive organs, but scientists aren’t sure whether a flatworm can fertilize its own eggs, or if eggs need to be cross-fertilized by another flatworm.

Did You Know?

• Flatworms look like "flying carpets" as they glide through the water.
• If you've ever seen a flat, jelly-like blob hiding underneath a rock or shell near the Bay's shoreline, it may have been a flatworm.

Sources and Additional Information

• Life in the Chesapeake Bay by Alice Jane Lippson and Robert L. Lippson
• Chesapeake Bay: Nature of the Estuary, A Field Guide by Christopher P. White