The nine-armed starfish (Luidia senegalensis) is a species that is classified in the Luidiidae family. It can be found in western areas of the Atlantic Ocean, with a range that includes the Caribbean Sea, The Florida coast, South American coasts, and the Gulf of Mexico. It prefers a habitat within muddy or sandy areas with plenty of seashells in protected areas like lagoons and can be found at depths of up to 130 feet.
The nine-armed starfish has a small, round body with nine long arms that extends from it, growing to a diameter between twelve to sixteen inches. A large number of plates occur on the upper side of its body and arms that hold spines and differ in color. The upper areas of the arms are grey while in outside plates are cream in color. Small, white spines occur along the edges of the arms as well as on the underbelly. The tube feet of this species are similar to those of other starfish, with suckers that help it remain steady and travel. These are slightly clear and orange in color. The mouth of this species occurs in the middle of its body disk. It can sometimes be confused with the gray sea star, which occurs in its range.
Like other species of starfish, the nine-armed starfish is both a predator and scavenger, feeding mainly on mollusks, polychaete worms, and crustaceans. These food types are consumed when the starfish turns its stomach inside out, covers its prey, and then digesting it slowly. This species is also known to dig itself into the sand, consuming small prey like brittle stars while it filters through the sediment. Individuals in the Indian River Lagoon have been found to have small polychaete worms residing on their body, living in a commensal relationship.
The breeding season of the nine-armed starfish varies depending upon the area of its range, but this species breeds the same way. Both males and females release their gametes simultaneously into the water column. Once eggs are fertilized, they develop into bipinnaria larvae that become part of the plankton in the water. After about twenty-five days, the eggs are large enough to fall to the sea floor and undergo metamorphosis into young starfish.
Image Caption: Nine-armed Starfish. Credit: Andrea Westmoreland/Wikipedia (CC BY-SA 2.0)
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