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Sea Life, Animals
& Exhibits

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Chocolate Chip Sea Star

(Protoreaster Nodosus)

Like a chocolate chip cookie, this sea star has dark brown pointy horns shaped like chocolate chips all over the top of it for protection. The Chocolate chip sea star has a thick body with five thick radially symmetrical arms arranged around a central body disk, which contains all of the internal organs. Although sea stars are invertebrates, they have a skeleton. Their skeleton, however, is not made of bone. It is calcareous or made of a calcium-based rocklike substance. The skeleton is made up of small plates that easily move to give the sea star flexibility. Sea stars crawl across the seafloor using rows of tube like feet on their arms for locomotion. They use an internal plumbing system called the water vascular system. It is a system of water canals that run throughout the body. Water is sucked into the sea star through a small hole on the top of the animal. The ends of the canals can be found on the animal’s oral (underside) surface as tube feet. The tube feet move when there is a change in the water pressure within the canals. There are thousands of tube feet all over the sea star’s oral surface which are used for movement, capturing food and breathing. Sea stars can regenerate or regrow arms if they are bitten or ripped off by a predator or grow a new individual from a ripped off arm. Sea stars cannot see. They have an ‘eye spot’ on the end of each arm. The eye spot can detect changes in light and dark, but cannot make out distinct shapes, colors or details.

Habitat

Chocolate chip sea stars live in the warm areas of the Pacific Ocean, Indian Ocean and Red Sea. Found all over sea grass beds and sandy areas, these sea stars live in shallow water areas. They can also be found on coral reefs to depths of 100 feet.

Diet

They feed on sponges, coral, oysters, clams, algae, shellfish, bacteria and detritus or waste products and the remains of dead plants and animals. Since they do not have eyes, Chocolate Chip Sea Stars hunt using their sense of smell. Once they smell something they want to eat, the sea star carries itself over to its food. The mouth of sea stars is on the oral surface or underside of their body; the mouth lacks teeth. The star covers its food, then pushes out its stomach from inside its body and covers it. Stomach juices smother the food, and cilia or tiny hairs move its now gooey meal inside the sea star’s body. Sea stars have a unique adaptation for consuming bi-valve mollusks (oysters, clams, mussels, etc.). Stars insert a portion of their stomach into the small “gape” between the valves of a mollusk. Stomach enzymes are released and digest the fleshy part of the mollusk inside its own shell. The digested contents are moved back into the sea star leaving an empty bi-valve shell. Most bi-valve mollusks are at the mercy of sea stars, since their shells do not close perfectly.

Behavior

Chocolate Chip Sea Stars reproduce by spawning or releasing eggs and sperm into the ocean at the same time. Females can produce up to 65 million eggs per each spawn. Since the egg and sperm are spawned, fertilization or the joining of egg and sperm to form a tiny sea star is most likely to occur if a large number of sea stars have gathered in the same area and spawn at the same time. Sea stars go through five growth stages before coming to be the star-shaped animals with which we are familiar. During the first month, the sea star freely floats around looking like a tiny sea jelly or blob. It can barely be seen by the eye and feeds on tiny plants and animals floating in the ocean. The baby sea star then metamorphoses or changes shape into a star-shaped creature. For the next six months, the juvenile sea star slowly grows, finds a hidden home under reef rock and rubble, and begins feeding on algae. After they get big enough, these sea stars emerge and begin to travel the reef in search food. After two years the sea star stops growing and is developed enough to reproduce.

Predators

Although starfish are fairly well armored and generally ignored by most fish, several types of fish will view them as food, including triggerfish, pufferfish, boxfish and parrotfish. Also, other types of starfish are known to be cannibalistic and eat one another.