Brittle Star

By: Abby Kowalczyk

Integumentary System

The integumentary system is the outer covering of the body (skin, hair, nails etc..) The integementary system of the Brittle Star includes a thin cuticle, epidermis, and dermis. The dermis is very thick and is made out of connective tissues, it contains an endoskeleton of calcium carbonate that keeps the outer covering durable. The Brittle Star has a radial symmetry, some can be bilateral but most have the strongest tendency to be radial. On the Brittle Star there are five arms that connect to a middle disk. In the Brittle Star, the middle disk is much more prominent than it is in other starfish. There are no ears of nostrils on the Brittle Star but it does have a mouth. The mouth is located at the bottom of the star and it contains five teeth and very strong jaws. The mouth also doubles as the anus to get rid of waste. On each of the five arms of the Brittle Star there are short spins to protect the animal. The Brittle Star spins it's arms to move fast through the water. The Brittle Star is the fastest starfish there is. The color of the Brittle Star is primarily brown but can be blue, grey, and a variety of bright colors.

Brittle-Star Scuffle.


"Brittle Star." Wikipedia. Wikimedia Foundation, 15 Sept. 2014. Web. 23 Sept. 2014. <>.

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"Starfish." Wikipedia. Wikimedia Foundation, 25 Sept. 2014. Web. 24 Sept. 2014. <>.

Skeletal and Muscular System

The Brittle Star's skeleton is made of calcite ossicles in the form of bony plates. These plates are covered by epidermis and they cover the whole body. These plates give the Brittle Star protection and allow it to bend it's arms to the side. A thin ring of soft tissue surrounds each ossicle while it's also surrounded by four series of jointed plates. These fours plates are the upper, lower, and two lateral surfaces of the arm. The two lateral surfaces have many spines shooting outwards to help the Brittle Star move. The Brittle Star is very different from most organisms with radial symmetry. The Brittle Star uses it's arms to move in a motion perpendicular to their central axis, unlike most radial organisms which move in the same direction as their central axis. This odd feature allows the Brittle Star to move swiftly across the ocean floor using it's five arms. The way a Brittle Star moves can be compared to the way a four legged animal moves.


Works Cited

"Brittle Stars." N.p., Apr.-May 2010. Web. Oct.-Nov. 2014. <>.

"Echinodermata." The Muscular System. N.p., n.d. Web. 08 Oct. 2014. <>.

Parry, Wynne. "Brittle Stars Move Like Humans." LiveScience. TechMedia Network, 10 May 2012. Web. 08 Oct. 2014. <>.

Nervous System

The Brittle Star's nervous system is very simple. It revolves around a central disk, or nerve ring, that is in the center of the stars middle disk. The nerve ring is connected to a radial nerve that runs trough each arm. Since the Brittle Star has no eyes, or any way to see, it uses it's nerves to sense it's surroundings. The Brittle Star is able to feel if there are chemicals in the water, and if it's light or dark all by touch. The Brittle Star does not have a brain, so a ring of nerve cells sends information around the body.

Fun Fact

If one of the Brittle Star's rays is cut off, they are able to regrow the ray. Brittle Stars commonly use the method of detaching there own arms as a way to ward off a predator.


"Brittle Star." Wikipedia. Wikimedia Foundation, 15 Sept. 2014. Web. 23 Sept. 2014. <>.

"Brittle Star- Enchanted Learning" Col, Jeananda. Enchanted Learning, 2000.

The Respiratory System

The Brittle Star uses little sacs, known as bursae, for respiration. Water is sucked up through the mouth and go into the bursae, which are located on the underside of the central disk. The bursae have small cilia on them to direct water flow through the body, by doing so the body can absorb oxygen form the water. Then, the waste is expelled through the mouth.


Works Cited

About Education. "Brittle Stars." About. About, 2014. Web. 17 Nov. 2014. <>.

"Brittle Star." Wikipedia. Wikimedia Foundation, 18 Nov. 2014. Web. 17 Nov. 2014. <>.

The Circulatory System

The Brittle Star does not have a true circulatory system of blood vessels or a heart. To replace what the circulatory system does for most animals, the star has a system of tubes to move around nutrients and oxygen too all parts of the star. Gas exchange occurs in the bursae and then water flows, with help from the cilia, through sinuses and vessels within the body to distribute the nutrients and oxygen.


"Echinodermata." Circulatory System. Weebly, n.d. Web. 29 Nov. 2014. <>.

Kern, Angie. "Body Systems." *Brittle Stars*. Weebly, n.d. Web. 29 Nov. 2014. <>.

Digestion and Excretory System

The Brittle Star's diet includes small crustaceans, worms, and some stars filter feed. They uses their long rays to hold onto prey and bring it to their mouth where it is then eaten. Sometimes Brittle stars will stick out there rays and small bacteria and particles will get attached to the mucus coating on their rays and then they can eat the small particles off their arms. The Brittle Star has a very short digestion and excretory system in its body. It consists of a mouth that has five jaws that functions as both a mouth and an anus. Inside the mouth there is a stomach pouch and a small esophagus. Digestion takes place within the small ten pouches inside the stomach these are also known as ceca. This is where nutrients are taken from food to keep the body functioning properly. Once all the food is digested it exits the star's body through the mouth.

How a Brittle Star Captures Food

In the video below, it shows how the Brittle Star is able to use its long rays and spines to attach to prey and capture it meal in it's grasp. The Brittle Star is much different from a normal starfish because of the way it can move it's body and arms to survive in it's habitat.
Feeding the Green Monster Star Fish


"Brittle Star." Wikipedia. Wikimedia Foundation, 29 Nov. 2014. Web. 30 Nov. 2014. <>.

Peck. "Digestive." Digestive. Shorecrest, n.d. Web. 30 Nov. 2014. <>.

Reproduction System

The Brittle Star's reproduction system is simple. Inside the disk of the star there are gonads, which are the reproduction organs, from there they branch out into pouches in between the arms. The reproduction process occurs externally by the stars releasing their gametes into the water. From there, the gametes need to be fertilized by another gamete of the opposite sex. Then the larvae grow on plankton and hope to survive. There is no difference between the male and female Brittle Stars other than if they had sperm of egg, there is no way to tell the difference without seeing the internal anatomy.


Dale, Johnathan. "Starfish Reproduction." Starfish Reproduction. N.p., 10 May 2000. Web. 06 Dec. 2014. <>.

Kern, Angie. "Body Systems." *Brittle Stars*. Weebly, n.d. Web. 06 Dec. 2014. <>.