The cushion star is a sea star that gets its common name from its inflated, pillow-like appearance. This species lives on coral reefs throughout the Indo-Pacific, and its species name (Culcita novaeguineae) reflects its discovery and commonness in New Guinea. Juveniles look like typical sea stars, but as the cushion star grows, it becomes more inflated and the arms grow together, eventually reaching a point where they are almost no longer discernible. On the underside, however, the cushion star clearly shows its five-part symmetry, particularly near the mouth.
The cushion star, like all sea stars, moves on a system of tube feet, so called because they are operated by a hydraulic system controlled by the main body. They are known to prey on corals and other sedentary animals, as well as decaying organic matter. They feed by inverting their entire stomach, through the mouth, and digesting the soft tissue off of a coral’s skeleton or the meat out of a clam, right in the open environment, and sucking down the available nutrients. Cushion stars reproduce through a behavior known as broadcast spawning, where several females release eggs and several males release sperm into the water column above the sand, all at the same time. This method increases the likelihood that eggs will become successfully fertilized and that fertilized eggs will not be eaten by egg predators near the reef.
Colors vary widely within this species, from orange to red to brown to green. People do not eat cushion stars, but some are collected to be dried and sold in tourist shops. The impact that this activity has on cushion star populations is unknown. Scientists do not have sufficient data to determine this species’ population trends, but as residents on coral reefs, human induced changes to this vulnerable ecosystem may also threaten the cushion star and other species.
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