Range: West coast North and Central America

Habitat: Shallow shores to 100 feet (30m)

Size: 1 foot (30cm) tall and 1 foot wide (including tentacles)

Diet: Crustaceans, fish, molluscs, and more

Threats: Sea snails, sea star, and sea spiders; also pollution

Lifespan: One hundred or more years estimated

Transcript:

Today on Animal Fact Files we’re discussing giant green anemones. This invertebrate has earned its common name as it is both one of the largest living anemones known today, and it's green! Giant green anemones get their green color from pigments present in their own body, and from symbiotic algae that live inside them. That might sound like body horror, but it's a mutual relationship: the anemone gets nutrients from the algae's photosynthetic nature, and the algae gets a safe place to live. Like other anemones, these green giants are cnidarians; they have stinging cells to ward off predators.

While this defense system keeps away most animals, some brave the tentacles of this marine giant and take a bite. Predators to giant anemones include sea snails, sea stars, and sea spiders. As you can likely guess, giant green anemones live in the sea, and they are most frequently found along the West coast of North and Central America from Alaska to Panama. They're shallow water inhabitants, typically living no deeper than 100 feet (30m) below the waves. In fact, these invertebrates often purposefully settle in areas they know they'll have easy access to food.

It might seem like an animal that doesn't move once it's cemented itself to its home location wouldn’t be considered a carnivore, but that's exactly what a giant green anemone is! When they aren't enjoying the nutrients provided by their houseguests, these animals dine on sea urchins, small fish, crabs, and mussels that have become detached from the sediment. It's not uncommon to see a giant green anemone growing among mussel beds for this very reason! Often these cnidarians are described as solitary animals, however, it's not uncommon to see over a dozen per square meter (10.7 square feet) in these food-heavy habitats. 

In size, these invertebrates can reach nearly a foot (30cm) across including their stinging tentacles and stand just as tall as max height. That's almost as big as Chester! When disturbed, they retract into themselves until they feel safe once again. Their tentacles gather food and deliver it to the mouth in the center of their oral disc. 

Giant green anemones are gonochoristic, they display separate sexes, but you wouldn't know by looking at them. Their tentacles can range from green to blue, but never show off pink tips like some of their relatives. They also lack bands across their oral surface, or only display extremely faint bands that are nowhere near as defined as the dark bands in other species.

Giant green anemones spawn in summer with some overlap into spring and autumn depending on where they live. The eggs are fertilized externally in the water column and hatch into larvae that float around for a few days before finding a place to settle. Some other anemones, including the congeners of this species, can split and reproduce asexually, as well, however, giant green anemones do not do this.

It's unknown how long these invertebrates can live in the wild, though some estimates put them at over 100 years old. Some individuals were kept in captivity for 80 years before they died due to neglect as opposed to what appeared to be any kind of senescence. Up until that time they spawned yearly and had no external signs of withering. These animals can't handle pollution, so they're at risk in areas where waters are impacted by this distress.

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