::Digestive System::
Inside anatomy of brittle star's disc
The mouth of the brittle star has five jaws. It serves the purpose of an anus, as well as a mouth. Behind the jaws is a short esophagus and a large stomach cavity that is located in much of the dorsal half of the animal's disc. Digestion occurs within 10 pouches of the stomach. These animals are mostly scavengers and brittle stars can eat small organisms if avaliable or in large crowded areas eating particles off the seafloor currents using its powerful jaws.
::Reproductive System::
Brittle Star larvae that is bilateral.
Brittle Stars are often separate sexes and the gonads are located in its disk. The gonads open into pouches in between the arms that are called the genital bursae. For fertilization, it is external with the gametes being shed into the surrounding water through the bursal sacs and this occurance usually happens at night. Some species of brittle stars and other stars can effectively give birth to live young, but most of the time, the larvae are in the free-swimming larval stage. Most brittle star babies have separate genders meaning male or female. The sperm or eggs depending on gender are stored in pouches in central disk (near gonads). There are no real differences between female and male other than the internal anatomy between egg and sperm.
LIFE SPAN:
Brittle Stars become sexually mature at about 2 years and at about 3-4 years become fully grown. Most brittle stars can live up to about 5 years old.
LIFE SPAN:
Brittle Stars become sexually mature at about 2 years and at about 3-4 years become fully grown. Most brittle stars can live up to about 5 years old.
::Respiration::
Respiration consists of the water-vascular system. This generally has one madreporite, which unlike sea stars is not on surface, and the water-vascular system enters into the madreporite and sieve plate, passes through the stone canal, and then traces a path from the ring canal encircling the mouth out to the five arms and then back out.
::Nervous System::
General nervous system image
Consists of a main nerve ring that runs around the central disc. At the base of each arm is a ring that attachs to a radial nerve that runs down to each limb. The nerves in each limb run through a canal at the base of the ventral ossicles. Because brittle stars have no eyes or other sensory organs, they have several types of sensitive nerve endings in their skin and are able to sense different chemicals in the water, with touch, and even sense the prescene or absence of light.
::Skeletal/Muscular System::
Cross-section of a brittle star arm
Brittle Stars pocesses a skeleton made of calcium-cabonate in the form of calcite. These calcite ossicles are fused together to form armor plates. These plates are covered with epidermis (skin) to create a smooth, strong covering. In most brittle stars, the joints between the ossicles and armor plates allow the arm to bend to the side, but not bend upwards. The ossicles are surrounded by a very thin ring of soft tissue and then by four series of jointed plates (upper, lower, and lateral surfaces of the arm). The two lateral surfaces often have a number of elongated spines projecting outwards which help to provide traction while the animal is moving.
::Circulatory System::
Gas exchange and excretion occur through cilia-lined sacs called bursae which each opens between the arm bases on the underside of the disk. Typically there are 10 bursae pouches and each fit between two stomach digestive pouches. Water flows through the bursae by means of cilia. Oxygen is transported throughout the body via a heral system (a system designed to distribute gases and nutrients), which is a series of sinuses and vessels distinct from the water-vascular system.