What Are Some Facts About Starfish?

One of the key facts about starfish is that they are not fish. Their correct name is sea star, which is much more descriptive. Let’s look at more facts about sea stars.  

Here are some facts about the structure of a starfish:

• They are echinoderms, which mean they are similar to sand dollars, sea cucumbers, and sea urchins. 
• They are a carnivorous invertebrate with a hard skin that offers protection from predators. 
• Many times starfish have spikes or protrusions on their skin. 
• Although most have five arms, some can have 50. 
• On their bottom side are small protrusions called tube feet. 
• These help the starfish move and also can open up clams and oysters.  

Diet of the Starfish

Here are some facts about what starfish eat:

• Clams and oysters have already been mentioned and starfish also like mussels, small fish, barnacles, and snails. 
• There are some species that will eat animals or plants that are dead and decomposing. 
• Some, like the crown-of-thorns starfish, will eat coral polyps, plankton, or sponges. 
• Starfish have two stomachs. 
• One of them allows them to eat things that are bigger than their stomachs.  When they are eating something like a bivalve, they pull open the shell just a bit and push their cardiac stomach into the shell, digest the animal, and then slide it back. 
• Back inside, the cardiac stomach transfers the food to the pyloric stomach.  So the cardiac stomach does its digesting inside out.   

Species and Habitat of the Starfish

There are around 2000 species of starfish that live in all the earth’s oceans. 

• They are not found in fresh water. 
• They can range from 4.7 to almost 20 inches in width, but most measure 12 inches or under. 
• They can live up to 35 years in the wild. 
• One of the most interesting facts about starfish is the starfish has the ability to regenerate an arm or even most of its body. 
• Most of a starfish’s important organs are in their arms. 
• When one is damaged or cut off, a new one will take its place. 
• Some species need the central part of their body, or disk, to regenerate, but some can grow a whole new body just from a part of an arm. 
• This does not happen quickly as it can take a year to grow an arm back.

Starfish Life Cycle

Here are the general facts about the way starfish reproduce:

• Most species have separate sexes, but some are hermaphrodites. 
• Fertilization takes place externally as both the male and females release their gametes into the water. 
• They are in the same general location and will take signals from one another to know when each is ready. 
• The fertilized embryos become part of the zoo plankton in the environment.
• Some species reproduce asexually with a section of an arm breaking off and growing into a new starfish. Usually, for this kind of reproduction to take place, part of an arm and a section of the central disk are required.

Other Starfish Facts

Here are some other fun starfish facts:

• Starfish do not have blood, but they have a water vascular system.  Sea water is pumped into the tube feet to lengthen them.  Starfish also do not have a brain.  Their nervous system is spread throughout their arms.
• Starfish have tiny eyes at the end of each of their arms.  These help them sense movement and observe the difference between dark and light.  There is no iris or cornea, and the eyes are more like sensors.  
• Starfish are also sensitive to temperature, touch, their environment a far as location is concerned, and the water that is all around them.  The tube feet are very sensitive to chemicals, which helps them locate food.
• Because of the way they use sea water, starfish have no ability to filter toxins in the sea water.  They can be easily damaged from pollutants in the water.  Oil spills and other contaminants have a very negative effect on the starfish population.  Other threats to them include humans, birds, and sea otters.

Starfish are an interesting animal upon which little is known by most people and much is misunderstood. Whether you call them a starfish or a sea star, this is a fun animal to study regardless of your age.