Asterias rubens

Common Starfish

Domain: Eukaryota Kingdom: Animalia

Phylum: Echinodermata

Class: Asteroidea

Order: Forcipulatida

Family: Asteriidae

Genus: Asterias

Species: rubens

Taxonomy

Biome

Marine

(Benthic Zone)

Characteristics/Adaptations

A starfish has tube feet. This allows the organism to walk, capture prey, pry open shells, and stick to rocks in strong currents. It also give the starfish the ability to stick to the bottom of structures underwater. This is an important way that this species hides from predators.
Starfish have a water vascular system. This system controls the tube feet to carry out the actions that are needed for survival.
Like the fire salamander, a starfish can regenerate its body parts. They can regrow arms for walking or capturing prey. Starfish also have the ability to regrow any organs if they are harmed as well.
Starfish have spines that grow on their back. This protects them from predators, especially because it is very unpleasant to eat.
Pincers are organs that allow the starfish to keep algae and other organisms from growing on it. This is very helpful to the starfish because they are very slow moving.
Starfish have a stomach that extends outside of their body. This gives them the ability to feed on prey that is bigger than its mouth.

Oxygen & Carbon Dioxide Exchange

A starfish primarily gets its oxygen through its tube feet. Oxygen enters the body through diffusion into the tube feet or papulae on the upper surface of the body. The oxygen is then transferred into the water vascular system. The area around where the oxygen diffuses is abundant with cilia that move to produce a current. This current brings fresh water so that the starfish can absorb oxygen and freshens the water where the starfish excretes carbon dioxide.

Circulation and Excretion

Circulation occurs in three places: perivisceral coelom, water vascular system, and hemal system. Starfish have an open circulatory system with cilia circulating fluids throughout each arm. Instead of having a heart, starfish have a system of tubes that takes the place of the average circulatory system. The water vascular system provides water pressure that operates the tube feet by the movements of water from the ring canal, t the radial canals, and then ending in the tube feet.

When a starfish needs to get rid of waste, it excretes it through the anus or the water vascular system. Its urine is excreted through its tube feet. However, it is interesting because a starfish has no organs to aid in any excretory processes. Instead, they have cells that take waste particles and move it through tiny openings to eliminate it from the body.

Nutrients

After a starfish has captured its prey (typically a mollusk, clam or oyster), it wraps itself around the creature and breaks the muscles that hold the shell together. It then pushes its cardiac stomach out of its mouth and eats the contents of its prey whole. When it has consumed its victim, it then re-swallows its stomach and begins to digest the food it has just obtained. This stomach is then connected to another stomach called the pyloric stomach, located just above it. Digestive enzymes break down the food in both stomachs and the nutrients are then absorbed throughout the pyloric ceca for transport to the rest of the body.

Resources

7716

Info: http://animaldiversity.org/accounts/Asterias_rubens/

http://www-tc.pbs.org/kqed/oceanadventures/educators/pdf/Treasures-Adaptation-Chart-Answers.pdf

http://www.whatdostarfisheat.info/

http://www.madreporite.com/science/digest.htm

http://animals.mom.me/feeding-respiration-starfish-6596.html

http://wiki.hicksvilleschools.org/groups/hsbiology/wiki/6fcaa/Excretory_System.html

Phylogenetic Tree: http://www.deftstudios.com/bioweb/bioimgsm.htm

Reception and Response

Starfish do have the sense of vision. They have small sensors that are located at the ends of the starfish’s arms. There are sensory neurons right beside these eyes so that the brain can interpret the light. Another key sense of a starfish is its ability to perceive touch. The tube feet underneath the starfish have receptors that are very sensitive to touch, especially the temperature of water. If the water is too hot or too cold, it will know to move to an area where the water is capable of supporting it.

In all, starfish sense their environment and learn from it so that they are better able to seek out food and avoid danger.

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