Metridium Senile

By Scott Boyd

The Frilled anemone (Metridium Senile) is commonly misidentified as its larger cousin, Metridium Giganteum. Both are often referred to as a Plumose anemone, which historically, is actually a typographic error in an old biology text (for “Plumed” anemone). The frilled anemone is much smaller and is somewhat transparent as opposed to its giant cousin which varies from bright white to orange, has a thick column and a lobed oral disc.

Metridium Senile grows to a height of only about 4 inches. Its column may be white, cream-colored, tan, brownish or light orange in color, with hundreds of small, thin tentacles which are usually grayish or white. When disturbed, it will discharge long, white strands of stinging cells, which are used to paralyze its prey.

The frilled anemone produces both sexually and asexually. It feeds upon small zooplankton (primarily copepods and larvae) which are captured by its fine tentacles and paralyzed by its nematocysts. Several nudibranchs feed upon the frilled anemone as well as a few predatory sea stars.

This species is most commonly found on hard substrates, attached to floats, pilings, rocks and other solid objects, from the intertidal zone to depths of less than 100’. This anemone is very common on our coast from Alaska to southern California, as well as both northern coasts of the Atlantic ocean.