Biology/Natural History: This species has sometimes been mistaken for Corella willmeriana, which has a larger geographic range and lives deeper. The eggs of this species float (due to replacement of sodium by ammonium in follicle cells) and are thus trapped in the atrial pocket, which extends upwards. After hatching as tadpole larvae, they swim for a short time (minutes to hours) then settle and metamorphose. Many larvae often settle in the same place (on clean surfaces), leading to aggregated adults. At Friday Harbor, the species becomes mature at 3-4 months and lives for 5-8 months. Breeding is year-round. They have 12 chromosomes. Predators include the flatworm Eurylepta leoparda and the seastars Mediaster aequalis, Solaster dawsoni, and Pteraster tesselatus. The colonial tunicate Diplosoma macdonaldi may overgrow it in the winter months. White flecks seen in the mantle are uric acid crystals. The species concentrates iron but not vanadium. One can observe the periodic reversal of blood flow in this species.