|Size||4.7-9.4 inch (12-24 cm)|
|Weight||Up to 11 lb (5 kg)|
|Lifespan||Up to 34 years|
|Predators||Fish, rays, sharks|
|Habitat||European and African coasts|
|Characteristics||Star-shaped body, mostly five arms|
There exist about 1,600 starfish species. They mostly have five arms attached to their disc-shaped body and measure almost eight inch (more than 20 cm) in diameter. The arms cannot always be easily detected. There are starfish that look like spheres or like sea urchins. They are called cushion sea stars.
Anatomy and Appearance
Starfish Don't Have Brains
Patrick Star from SpongeBob is not a particularly dumb starfish, but has – like its real fellow species – simply no brain at all. But seriously: Scientists have found out that starfish are able to act intelligently in a way despite of this. Yet they cannot solve maths problems.
The Biggest and the Smallest Starfish
The sunflower sea star is the biggest starfish with a width of 35-40 inch (90-100 cm) from arm to arm. The smallest starfish, Patiriella parvivipara, has a width of just about 0,4 inch (1 cm), which is about as much as a fingernail.
How Many Arms Does a Starfish Have?
Many starfish have five arms. The starfish Labidiaster has the most arms – about 40 to 50 of them, yet they look more like the tentacles of a jellyfish.
Starfish Turn Their Stomach Inside Out
Starfish open seashells with their sucker cups. After that, it turns its stomach inside out. If this isn't a bit disgusting by now, it will become now: The starfish injects its digestive juices into the seashell. After a few hours, the shell contains a kind of mussel pulp that can be comfortably slurped by the starfish.
Senses and Abilities
Do Starfish Have Eyes?
On every arm, starfish have an "eye". Yet, they cannot really see but only differentiate between light and dark.
How Deep Do Starfish Dive?
Starfish have been detected at depths of 32,800 feet (10,000 meters) in an ocean trench near the Philippines.
Starfish Regenerate Lost Arms
Mussels are one of the favorite dishes of the starfish. Fishermen were not very happy about this. In order to prevent them from eating the mussels, they simply cut them in two halves. This was not very clever, because it caused a real starfish plague. The two halves developed into two genuine starfish with a rather big appetite. They had to eat a lot to regenerate their bodies. A starfish can even regenerate from a single arm.
How Old Do Starfish Get?
Normally starfish do not get older than a few years. This does not apply to the species Pisaster ochraceus, which can get up to 34 years old.
Starfish are rather “creative” when it comes to reproduction. Normally the female animal lays the eggs and the male animal discharges its semen into the water, 2 to 100 millions, depending on the species. Yet, starfish do not grow from fertilized eggs. If an arm is cut off or a starfish is cut into two halves, a new starfish could grow from it.
Are There Venomous Starfish?
Yes. But if you live near the Mediterranean Sea, you're lucky. There are no venomous starfish. The home of venomous starfish are tropical coral reefs, for example the crown-of-thorns starfish. Its body is covered with 1.6 to 2.3 inch (4-6 cm) long spines. If a human gets hurt by the spines, it can cause headaches, sickness and even paralyses.