Find out all about these incredible invertebrates!
Grab your snorkels, gang, and join us as we discover the secrets of one of the ocean’s most peculiar creatures! Ready? Then check out our fascinating starfish facts…
Family: Asteriidae Classification: Invertebrate
IUCN status: Not Evaluated
Lifespan (in wild): 35 years
Weight: Up to 5kg
Body size: 1-65cm, depending on species
First things first – despite their common (and very misleading!) name, starfish (or sea stars) are <not> actually fish. Since they don’t have a backbone, they belong to a group of species called invertebrates, which also includes urchins and sponges.
There are around 1,600 different species of starfish living in the world’s oceans, where they occupy every type of habitat including tidal pools, rocky shores, sea grass, kelp beds and coral reefs. Some kinds of starfish are even found on sandy seabeds 9,000 metres deep! Most starfish sport spiny skin and five arms surrounding a central disk-shape body – although some can grow as many as 50 arms. Their arms are covered with pincer-like organs and suckers that allow the animal to slowly creep along the ocean floor. They also have eyespots on the tips of the arms, which allow the starfish to sense light and dark, and help it find food.
Favourites on the starfish’s menu include mollusks like clams, oysters and snails. And it has a pretty impressive way of eating! After attaching its body to the chosen prey, the starfish extends its stomach out through its mouth. Substances (called enzymes) from the stomach then begin to digest the food. This allows the nutritious grub to pass inside the stomach, which in turn retracts back into the body where digestion is complete. Cool, eh? Tiny organisms that fall victim to the super starfish can be swallowed whole.
Starfish predators include certain fish species, sharks, manta rays and even other starfish! To help protect themselves, these incredible invertebrates have evolved several effective defense mechanisms. As well as their tough, prickly, armor-like skin, some have striking colours that camouflage them amongst plants and coral, or scare off potential attackers. And check this out, too – these cool creatures are able to regrow lost or damaged limbs! If under attack, some starfish will even shed an arm to escape the predator. Cunning stuff!
Starfish aren’t social creatures – instead they are solitary and spend most of their life alone. They will, however, sometimes congregate in large groups during certain times of the year to feed.