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A common name for this echinoderm is the sunflower star fish, but it can also be called Pycnopodia Helianthoides. It is the largest sea star in the world and can have an arm span of up to one meter long. Sunflower sea stars can have from 16 to 24 limbs and they can come in a large range of color such as yellow, orange, red, purple, or brown. They usually have a soft, velvet textured body and suckers on their many arms.

Where Are They Found?

Sunflower sea stars are mainly common to the Pacific Ocean. They can be found from Alaska to Southern California, but the largest sea stars can be found in Puget Sound, British Columbia and Alaska. They mainly live in the area between high water mark and low water mark of the shore where there is an abundance of seaweed and kelp.

Biology

Most sea stars have a mesh-like skeleton that protects their internal organs. They can also have about 15,000 tube feet on the underside of their body. To eat their prey, sunflower sea stars can extend their stomach outside their mouth to digest larger prey such as gastropods like the abalone. A very special characteristic of this animal is that it can shed arms when stressed and grow them back within a few weeks.

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Reproduction

Sunflower sea stars can reproduce asexually through fissiparity. If a part of the nerve ring in the center of the sea star comes off with an arm that is shed, that individual arm can eventually develop into another sunflower sea star. They may also reproduce sexually through broadcast spawning. This is when sperm and eggs are released into the water and fertilization occurs externally. To do this, they will arc up using their tube feet and release the gametes into the water. Sunflower sea stars breed from May to June. For two to ten weeks, the microscopic larvae will feed near the surface of the water and are free floating plankton. After this phase, they settle at the bottom of the sea and transform into young sea stars. They start out with five arms and grow the rest of the arms one would see in mature sea stars. The average life span of most sea stars is 3 to 5 years.

Ecology

Sunflower sea stars can be very efficient predators, moving at one meter per minute. Their favorite prey is the sea urchin, and as a result, they can be commonly found close to where the population of sea urchins has gone unchecked and is very high. In addition to sea urchins, they eat clams, snails, abalone, sea cucumbers and may even cannibalize other sea stars. they have also been observed to eat dead dying squid. Although they can be efficient hunters, they are still preyed on by the king crab.

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