Last Reviewed and Updated on July 19, 2022
Starfish or sea stars are marine animals that we usually associate with the shape of a five-pointed star. But they can have many, many more arms. Explore some of the most interesting facts about starfish, from their lack of some organs we take for granted to their amazing regeneration abilities.
1. Starfish is not a fish
Their name suggests they might be fish, but in fact, they are not. Starfish are echinoderms. They are closely related to sea cucumbers, sea urchins, and sand dollars.
2. There are almost 2000 known species of starfish
There is much room for diversity when it comes to starfish, as there are almost 2000 different species of them. They can be found across the globe, from warm tropical regions to polar regions.
3. They are also called sea stars or asteroids
The most commonly known name for this group of animals is the starfish, however, they are also commonly called sea stars and even asteroids.
The name asteroids come from Asteroidea, the name of the class these animals belong to.
4. Most have 5 arms, but they can have more
The majority of starfish have 5 arms, but species with six or seven arms are fairly common too. A few species even have more.
Crown thorn starfish can have up to 23.
5. Labidiaster annulatus can have over forty arms
Labidiaster annulatus, known under the common name the Antarctic sun starfish or wolftrap starfish, has anywhere between 40 and 45 long narrow arms.
These starfish are found around the Antarctic Peninisula, South Georgia and the asouth Sandwitch Islands.
6. Starfish can reproduce both sexually and asexually
It’s always handy if you have alternatives. Most species of starfish are gonochoric, with female and male animals needed for sexual reproduction, although some species are hermaphrodites.
Asexual reproduction usually takes place by fissure, with the central disc breaking into two pieces, and each regenerates the missing part. The results are starfish clones. This type of reproduction has been observed in some of the starfish species.
7. A whole new starfish can grow from a severed limb
Apart from the usual types of reproduction, the starfish’s amazing regenerative abilities also breathe life into a brand new organism, a clone. A starfish is able to regrow a severed limb. However, if the severed limb contains just a little part of the central disk, the limb will also regenerate. A whole new starfish will grow from said limb. Pretty neat.
8. Starfish don’t have a brain
Starfish is one of the few animal species that don’t have a central brain. They do have a complex nervous system with the nerve ring around their mouth and nerves running along their arms.
Also, read what are some other animals without a brain.
9. They move around with hundreds of tube feet
Their arms are covered with many tube feet, and these tube feet are operated by a hydraulic system, a water vascular system. Starfish move by contracting muscles to force water into the tube feet, which makes these feet extend and push against the ground. They then relax the muscles for the tube feet to retract.
10. Many species eject their stomachs from their body to eat
This may just well be one of the weirdest facts about starfish. To eat, they will eject their stomachs from their body, covering their prey and partially digesting them. Once the food is partially digested, a starfish will draw the food and the stomach back in and continue digesting it. Pretty cool, right?