Please view these links for a step-by-step example of starfish dissection!
Starfish eat mostly mollusks, like clams and oysters. Their suction cup tube feet suck the clam and then their mouth swallows it. They will also eat fish, and there have been some instances where starfish turn cannibalistic and eat other starfish. Because they eat meat, they are classed as carnivorous. In order to eat their prey, starfish clamp their arms over the shell of their prey (if it is a mollusk) and pry the shell open slightly. Then the starfish will push its stomach out through its mouth and into the small crack in the shell of its prey. The digestive juices of the starfish will then make short work of digesting the clam or oyster, leaving only an empty shell behind. It is easier for a starfish to simply eat a fish because it does not have to open a shell, but starfish prefer clams or oysters. On occasion starfish will eat coral or crabs that they find on the beach.
Because starfish are slow-moving they do not prey on any animal that can swim too fast. If a starfish is desperate for a
meal, they may eat dead sea creatures that they find in the water. When a starfish surrounds its meal of a clam or oyster, it must exert a lot of pressure to get the shell of the animal to open even a crack. Larger species of starfish can exert up to twelve pounds of pressure to open the shell of its prey!
Here is a link to a really cool video of a starfish eating a mollusk!
Ring Canal=Circular canal in which filtered water enters through the madreproite and branches out into the radiated canals.
Rectal Cecum= Lateral duct of the terminal part of the digestive tract, where waste is stored before being expelled through the anus.
Anus= Terminal orifice of the digestive tract allowing waste to be ejected; most of the undigested food is regurgitated rather than expelled through the anus.
Stomach= Dilated section of the digestive tract preceding the intestine; it receives food to be digested.
Gonad= Each of the two glands located in each arm, producing gametes depending on the sex of the starfish (witch the starfish can change and choose it’s sex).
Pyloric cecum= Radiated duct of the digestive tract producing digestive enzymes and also allowing digested food to be stored.
Genopore= Dorsal opening through which gametes are expelled into the water to be fertilized.
Intestine= Section of the digestive tract between the stomach and the anus were absorption of nutrients is carried out and waste is transformed into fecal matter.
Radial Canal= Canal running the length of the arm; it receives water from the annular canal, which then passed into the tube feet.
Ampulla= Bulb that contracts to let water enter the tube foot, allowing it to extend; when it dilates, the foot retracts.
Esophagus= Muscular membranous channel of the anterior section of the digestive tract; it allows food to reach the stomach.
Mouth= Anterior cavity of the digestive tract located on the central surface that allows food to be ingested.
Tube Foot= Small flexible tube extending and retracting with the action of ampulla; it mainly allows the organism to move about, anchor itself to a support and capture its prey.
Central Disk= Central region of the body; the starfish’s arms are attached to it.
Spine= More or less movable outgrowths of calcareous plates forming the skeleton and enabling the starfish to ward off its predators.
Eyespot= Small light-sensitive structure located at the terminal end of each arm, allowing it to locate surfaces and prey.
Madreporite= Porous dorsal plate that allows water to enter the body; it connects the ambulacral ossicle to the outside world, and thus ensures locomotion.
Arm= Movable appendage radiating around the central disk; it has a mainly tactile and olfactory function. The starfish can regenerate an amputated arm.
students about anatomy using a hands-on technique. Echinoderms are
radial symmetrical animals that are only found in the sea because there
are none of land or in fresh water. Echinoderm means "spiny skin" in Greek. However, not all of them have spiny skin. Radial symmetry means that
their body is shaped like a bicycle wheel. It is said that there are over 6,000 species of starfish. They usually have five arms or rays called
appendages. Most adult echinoderms live on the bottom of the ocean
floor. A lot of them have suckers on the end of their feet that are
used to capture and hold their prey or to hold onto rocks in a swift
The sea star is not a fish like
most people would assume. The sea star is an echinoderm. There are over 2,000 species of sea star in the world's oceans, some that live in the
warm waters of the tropics to the cold waters of the Arctic. The common
sea stars will have four to five arms but there are species that will
have up to forty arms that are rarely seen. The skin of the sea star is
very rough and hard which protects them from the dangers of the deep oceans. Bright or matching colors of their habitat help them hide and scare
off creatures wanting a meal. The sea star's ability to regenerate its arms has made it famous among the scientists that study them. The sea star can actually regenerate its whole body from just one arm. The arm is the most important part of the starfish. Starfish have the ability to swim very well in all directions considering they have five arms.
The sunflower starfish is one of the larger
starfish species. It has 24 arms and can
reach a diameter of over 2 feet. The color
of this starfish can either be purple, red, pink,
brown, orange, and yellow. It is common
along the pacific coast and is found along the
rocky sea bottoms from Alaska to southern California.