Metridium farcimen, commonly known as ‘giant feather anemone‘, is a species of anthozoan of the family Metridiidae belonging to the order Actiniaria. The genus name ‘Metridium‘ derives from the Greek ‘metra‘, meaning womb or uterus, and refers to the body shape of these anemones, while ‘farcimen‘ comes from Latin and means ‘stuffed‘ or ‘abundant‘, describing their spongy and dense appearance. Metridium farcimen is distributed mainly in the cold waters of the Pacific Ocean, along the west coast of North America, from Alaska to southern California. It is commonly found in coastal marine environments, from the shallow intertidal zone to depths of approximately 30 meters, inhabiting rocky surfaces, pilings, and other underwater structures, where it attaches firmly with its basal disc.
Metridium farcimen is one of the largest anemones known, reaching heights of up to 1 meter and diameters of up to 30 centimeters when fully extended. Its body is composed of a long, slender cylindrical column, crowned by a broad oral disc surrounded by numerous thin, feathery tentacles, which can be retracted when the anemone feels threatened or is at rest. The coloration of Metridium farcimen varies from bright white to beige, light brown or sometimes pale orange. This species is distinguished from other similar anemones, such as Metridium senile, by its larger size and the density and length of its tentacles. In addition, the tentacles of Metridium farcimen are thinner and more numerous, giving the crown of tentacles a more feathery and lush appearance.
The feeding habits of Metridium farcimen are opportunistic and carnivorous. This anemone feeds mainly on plankton and small marine organisms, such as copepods, crustacean larvae, small molluscs, and other invertebrates that become trapped in its tentacles. The tentacles are covered with nematocysts, which are specialized stinging cells that immobilize or kill prey on contact. Once captured, the prey is transported to the oral disc by a coordinated movement of the tentacles and then ingested through the mouth located in the center of the oral disc. Due to its size, Metridium farcimen is also capable of capturing larger prey than other anemone species.
In terms of reproduction, Metridium farcimen can reproduce both sexually and asexually. Sexual reproduction involves the release of gametes into the water, where fertilization is external. The resulting larvae, known as planulae, swim freely for some time before settling on a suitable substrate and developing into a new anemone. Asexually, this species reproduces by pedal laceration, a process in which small fragments of the basal disc break off and develop into complete individuals, allowing Metridium farcimen to rapidly colonize new spaces in their environment.
An interesting fact about Metridium farcimen is its remarkable ability to adapt to different environmental conditions. It can survive in a wide range of temperatures and salinity levels, allowing it to thrive in diverse marine habitats. In addition, this species shows a high tolerance to pollution and can be found in areas close to ports and harbors, suggesting a high resistance to environmental stressors. Metridium farcimen is also known for its ability to contract rapidly when it feels threatened, drastically reducing its size to protect itself from potential predators or physical harm. This adaptation, along with its imposing size, makes it one of the most fascinating and resilient anemone species on the Pacific coast.
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