Range: Marine waters worldwide Habitat: Varies by species Size: Less than 1 inch - 3 feet (2.54cm-0.91m) long Diet: Clams, debris, zooplankton, and more Threats: Bottlenose dolphins, wasting disease, and more Life span: Up to thirty-five years

Transcript:

Today on Animal Fact Files we’re discussing sea stars. The sea stars’ scientific name is out of this world which just lends to their space themed common name. Of course, this name is also in reference to their similar appearance to the five pointed star shape. Not at sea stars come with five arms, though!

Some sea stars, like the sunflower sea star, can have as many as 40 arms. There are upwards of 2,000 living, classified sea star species which leaves room for plenty of variety! The smallest sea stars are less than an inch (2.54cm) long, while the largest can be nearly three feet (0.91m) in length! And they don’t have a head or blood, though they do sort of have eyes.

Sea stars have ocelli at the ends of their arms which are simple eye spots that are used to detect light. These echinoderms also have a water vascular system instead of blood and blood vessels. A sea star will pump water throughout its body and this is what helps the sea star move around. These animals have tube feet that either end in suction cups, which adhere to hard surfaces, or points which help them traverse a sandy landscape. Sea stars are only found in marine environments, but they can be seen in every ocean of the world. They’ll live anywhere from intertidal zones to the abyss.

Sea stars can sit near the top of the food chain in some habitats. For example, the crown of thorns sea star is well known for its destructive behavior on coral reefs. Some sea stars may eat floating debris caught in a mucus covering their body, while others can catch fish! Other sea stars may pull apart clam shells to eat the soft creature inside, and some sea stars push their stomach outside of their body and engulf their prey with it. They then release digestive fluids that help break down the prey until it is jello-y enough to be pulled back into their body along with the stomach.

For the most part, adult sea stars are safe from predation. I dunno about you but I’m not sure I could get past that crunchiness… Apparently bottlenose whales can deal with the crunch, though, because they eat adult sea stars. Adult sea stars can also be impacted by wasting disease which basically turns them into goo. Baby sea stars are more likely to face predation.

Many sea stars breed by spawning with males and females synchronously releasing sperm and eggs into the water column. Some species are hermaphroditic and have both male and female organs. These may brood their eggs instead of sending them out to sea. For those that do partake in broadcast spawning, the fertilized eggs develop into larvae which float as easy to eat zooplankton until they’re developed enough to sink to the bottom.

Once settled on the seafloor, sea stars may live up to 35 years. Some sea stars can regenerate lost limbs or even clone themselves via a lost limb, though usually the center disc needs to be present for this to occur. Sea stars can regenerate because many of their organs are actually in their arms.

Sea stars are probably more commonly known as starfish, though there’s been a recent push to change this. Trust us, we’ve experienced it. We’ve covered nearly 500 different animals on this show and have discussed on many occasions how common animal names can change or how one animal may have multiple common names. And that’s not even considering all the different common names they have in separate languages. So if you get called out for calling a sea star a starfish, it’s okay. At the end of the day, animal classification comes down to the scientific name.

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