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The Explorer's Guide contains a treasure trove of aquatic science resources developed for use in K-12 classrooms. Back to Explorer's Guide.

Chocolate Chip Sea Star Scientific Name: Protoreaster nodosus
If one of their arms or part of their body gets bit off, they can regenerate or regrow it. As long as they don’t lose the central disc or the middle of their body, they can regenerate just about anything.

Region: Philippines

Like a chocolate chip cookie, this sea star has dark brown pointy tubercles or horns shaped like chocolate chips all over the top of it for protection. The chocolate chip sea star has five arms and can be found in a variety of shades ranging from light brown or cream to a brilliant deep orange. The 'chocolate chips' are variable in size, color and pattern between individuals. There aren't two chocolate chip sea stars exactly alike. Chocolate chip sea stars can be up to 16 inches (40 cm) long.

Found all over seagrass 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 (33 m).

Chocolate chip sea stars live in the warm areas of the Pacific Ocean, Indian Ocean and Red Sea.

Chocolate chip sea stars aren't picky eaters. They feed on sponges, bacteria and detritus or waste products and the remains of dead plants and animals. Since they don't 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 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.

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.

Sea stars can asexually reproduce. This means they can make an exact copy of themselves without eggs and sperm. Sea stars can regenerate or regrow arms if they are bit or ripped off by a predator or grow a new individual from a ripped off arm.

>A species or group of organisms that is in danger of extinction or disappearing from the face of the earth in the near future if its situation is not improved.

A species that can be found throughout its natural range but is declining in number and may become endangered in the absence of special protection efforts.

A species that is not declining in number but is of special concern because it is sensitive to pressure by particular human activities or natural events.

A species that is not declining in number and is not sensitive to pressures by human activities or natural events.

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Threats and Management
Chocolate chip sea stars that get too large for the home aquarium and may try to eat their tank mates.

While many sea stars are dried and used for arts and crafts, the chocolate chip sea star isn't often collected for this purpose. It is usually much too large for such purposes. People have not found many uses for these stars, keeping their population stable.

Did You Know?
While often called a starfish, these animals aren't actually fish; they're invertebrates or animals without backbones.

Although sea stars are invertebrates, they still have a skeleton. Their skeleton isn't made of bone though. It's calcareous or made of a calcium-based rocklike substance. The skeleton is made of tons of small ossicles or plates that easily move to give the sea star flexibility.

Sea stars have a unique means of moving. They use an internal plumbing system called the water vascular system. It's a system of water canals that run throughout the body. Water is sucked into the sea star through the madreporite or a small hole on the aboral surface or top of the animal. The ends of the canals can be found on the animal's oral 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't see. They have an eye spot on the end of each arm. The eye spot can detect changes in light and dark, but can't make out distinct shapes, colors or details.

Print Publications:
Allen, G. R. & Stene, R. 1996. Indo-Pacific Coral Reef Field Guide. El Cajon, California: Odyssey Publishing Company. 378p. ISBN# 981-00-5687-7.

Allen, G. R. 1997. Tropical Marine Life. North Claredon, Vermont: Periplus Editions Ltd. 64p. ISBN# 962-593-157-0.

Banister, K. & Campbell, A. 1988. Encylopedia of Aquatic Life. New York, New York: Equinox (Oxford) Ltd. 349p. ISBN# 0-8160-1257-101-X.

Colin, P. L. & Arneson, C. 1995. Tropical Pacific Invertebrates. Beverly Hills, California: Coral Reef Press. 296p. ISBN# 0-9645625-0-2.

Coleman, N. 1999. Dangerous Sea Creatures Aquatic Survival Guide. Australia: Neville Coleman's Underwater Geographic Pty Ltd. 95p. ISBN# 0-947325-24-7.

Coulombe, D. A. 1984. The Seaside Naturalist. A Guide to Study at the Seashore. New York, New York: Prentice Hall Press. 246p. ISBN# 0-13-79710.

Hoover, J. P. 1998. Hawai'i's Sea Creatures. A Guide to Hawa'i's Marine Invertebrates. Honolulu, Hawaii: Mutual Publishing. 366p. ISBN# 1-56647-220-2.

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

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Vocabulary Words

Aboral surface - The topside of the body.

Asexual Reproduction - Reproduction that does not involve the union of egg and sperm; results in an exact copy of the original animal.

Calcareous - Containing calcium carbonate; a hard calcium-based substance.

Cilia - Tiny hairs that are used for movement.

Detritus - The waste products of all the different types of organisms, including their remains after they die.

Extinction - An organism that has not been present on the face of the earth for over 50 years.

Eye spot - A light sensitive pigment that can distinguish between light and dark, but cannot determine distinct colors, shapes or details.

Fertilization - The uniting of egg and sperm to form a new individual.

Invertebrate - An animal without a backbone.

Juvenile - A young version of an adult.

Madreporite - A small hole on the aboral surface that draws water into the water vascular system.

Metamorphosis - A change in the body form of an animal when changing from egg to adult.

Oral surface - The underside of the body.

Organism - A living thing.

Ossicles - Plates.

Regenerate - The development of a missing part or the formation of a complete individual from a broken off part.

Spawn - The release of sex cells, eggs or sperm, into the water.

Species - A group of organisms capable of breeding and producing fertile offspring; organisms that share the same gene pool.

Tube feet - Clear fleshy extensions of the water vascular system that have a sucker at the end.

Tubercles - Small round protuberances on a bone or the body surface.

Water Vascular System - An internal plumbing system of connected water canals that run throughout the body. The ends of the canals can be found on the animal's surface as tube feet. This system makes moving, eating and breathing possible.

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Chocolate Chip Sea Star
Chocolate Chip Sea Star

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