Biology/Natural History: Growth rings may be prominent, especially in the northern parts of its range, as this species nearly ceases feeding in winter. Yearly growth lines are much less prominent farther south, but tidal cycle growth lines can often be seen. Mantle margin has tiny tentacles with tiny eyes. Pumps 2.51 liters of water per hour per gram body weight. Predators include Pycnopodia helianthoides, Pisaster brevispinus, and Cancer magister, and gulls. The cockle has a strong escape response to Pycnopodia--rapidly extending its foot and jumping away (movie). May be a source of paralytic shellfish poisoning (PSP) for humans. A simultaneous hermaphrodite. In Puget Sound they mature in their second year and spawn in July and August. Live 15-19 years in Alaska. May contain small pea crabs such as Pinnixa faba inside the mantle cavity.