Giant Keyhole Limpet
- A large gray oblong, oval shell with a single black central hole at the top of the shell, the portal through which waste products are released.
- Gray, black, or brown slimy mantle (body wall) covering the shell, unlike any other limpet that has mantle under the shell.
- Adult shell is 3-5 inches in diameter.
- Sessile animal, permanently attached to rocks.
- Monterey, California to Baja California, Mexico.
- Live in the intertidal zone.
- Found at depths up to 108 feet.
- Reproduce by broadcast spawning.
- Embryos develop into planktonic larvae and then juvenile veligers (tiny larvae with cilia to move in water) before settling somewhere permanently and growing into adult form.
- Filamentous cyanobacteria, diatoms, brown and red algae such as seaweed, seagrass, foraminifera, hydrozoans, bryozoans, nematodes, bivalves, gastropods, crustaceans, and tunicates.
- People use this species for medicinal uses.
- The primary predators for limpets are sea stars, birds, and the occasional crab.
- This species is one of the largest keyhole limpets.
- The whole on the top of the shell makes them different from true limpets, which release waste from the mantle beneath the shell.
- The blood of this species is used in many cancer treatments and vaccines, as it stimulates the immune system and its protein transports molecules throughout the body.
- A liter of blood from a keyhole limpet will produce 20 grams of protein, which can be worth as much as $100,000.
- Their shells were used as currency among Native Americans.
Sources: Harris and Markl, 1999; Harvesting blood from limpets for a cancer vaccine; How mollusk blood could cure cancer; Marine Biology. 8th ed.; Encyclopedia of Life; CaliforniaTidePools.com; sealifebase
Photo: Frederic Pache