Despite the name, starfish are not actually fish. They are echinoderms, a spiny skinned organism more closely related to sea urchins and sand dollars. Because of this distinction, marine scientists have been urging people to use the more proper term "sea star" when referring to these creatures.
Sea stars are some of the most iconic ocean creatures because of their instantly recognizable shape, but they are also among the more remarkable marine animals for many reasons including their anatomy, diet, habitat, and role in the overall eco-system. Here are some interesting facts about starfish that show just how amazing these organisms are.
Information About Starfish Anatomy
Sea stars usually have 5 arms. A lesser known species called the sun star or sunflower star, though, has up to 20 rays that extend outward.
Sea stars have no brain and no blood. They pump nutrients through their nervous system using sea water.
They can grow to be very large. While many you'll see washed up on shore or in tidepools are relatively small, they can weigh up to 11 pounds.
They can regenerate arms. Some can grow a whole new body from just one severed limb. It is a long process, though. A sea star that loses a limb can take up to a year to grow it back.
Starfish have eyes. While they don't see detail, there are eye spots at the end of each arm that can sense light and dark.
They can switch genders. While most are born as either male or female, some can change genders even several times during their life. In fact, the cushion star is always born male and some switch to female later.
Starfish Diet Facts
Their diet varies considerably by species. Some like the crown of thorns eat everything they can. Others like bat sea stars eat sea cucumbers, urchins, and even scavenged dead animals. Most eat bivalves such as clams, mussels, and oysters.
They eat inside out. Of all starfish facts, this may be the most bizarre - they consume prey outside their bodies. When they capture prey (usually clams or oysters), they use their tiny suction-cupped tube feet to pry open the shell. A stomach emerges (one of two stomachs) from the mouth, envelopes the prey, digests, and then returns to the body.
Sea stars can be cannibalistic. They are known to take down smaller individuals in their species. A particularly cannibalistic species is the chocolate chip sea star.
Starfish Habitat Information
They only live in salt water. While some sea star facts vary by species, one rule remains true for all. They cannot survive in fresh water. Only a few live near brackish water (a mixture of salt and freshwater).
They move using feet. Starfish have hundreds of tube feet located on their underside.
They move openly across the ocean floor. While many marine creatures, particularly those that like to live in coral reefs, tend to hide out in rocks and crevices to avoid predators, sea stars have a tough armor that protects them while they feed and move.
Other Star Fish Information and Sea Star Facts
- Typical predators of sea stars include otters, sharks, seagulls, rays, and some species of fish.
- Starfish don't typically touch during reproduction. They release eggs and sperm into the water where the two mix.
- Sea stars can live up to 35 years in the wild.
Did you know that our oceans are in danger? You can help protect one of these peaceful ocean dwellers today with a handcrafted starfish necklace and we will give up to 25% to conservation.