Starfish

What is a starfish?

These star-shaped creatures belong to the echinoderm family, alongside species like sea cucumbers and brittle stars. Starfish (Asteroidea), also called sea stars, have an interesting anatomy, fascinating habits and a varied appearance. They’re a big hit with aquarium visitors and those who love rockpooling, so let’s explore the most interesting facts about this group of marine animals.

What do starfish look like?

Five arms, a central disc, rough skin and a brown-ish orange colour – that’s the typical appearance of a starfish. This makes them pretty easy to spot, whether that’s in the wild or at an aquarium. However, there are around 2,000 species, all of which are different shapes, sizes and colours.

The number of variations is almost endless, from brown, red, and purple to pale yellow, blue, and grey. Plus, they can range in size from 10cm to 30cm, depending on their habitat and other factors.

Something they nearly all have in common, though, is their rough skin, which makes it difficult for predators to attack. The majority of them also have five arms, but it’s important to note that some can have up to 50 and still be classed as starfish! If you’re wondering why they’re not classed as legs, we’ve got the simple answer. On each of the arms are tube feet, which use hydraulic pressure to attach to various surfaces.

Their insides are even more interesting than their outsides. Starfish have a cardiac stomach and a pyloric stomach. The cardiac one can be ejected from the body, while the pyloric stomach remains inside. This adaptation allows a starfish to spit out its stomach through its mouth and wrap it around the food so it can be digested externally. This is particularly useful when starfish need to eat larger prey.

So, with these unusual eating methods, what do they eat? Since they’re a carnivorous group of marine animals, their most common prey are clams, oysters, snails, sponges, and other invertebrates.

Where do starfish live?

Starfish often inhabit tropical reefs, rocky shores, seagrass and cold seafloor habitats. However, a freshwater habitat is one place you won’t see a starfish species. This is because they can only survive in saltwater, so you won’t spot them anywhere except the oceans.

Starfish at Tynemouth Aquarium

Our starfish tanks can be found in the St Mary’s Island exhibit at Tynemouth Aquarium. From spiny starfish to chocolate chip starfish, learn about each species we have here and which tank you can find them in.

Common starfish (Asterias rubens)

Mostly found in the north-east Atlantic Ocean, this is the most common starfish species on the planet. With five arms, an orange-coloured appearance and pale spines, there might be plenty of them, but that doesn’t make them any less exciting as a species.

Purple sunstar (Solaster endeca)

The purple sunstar species, mostly spotted along the British coastline, typically has 9 or 10 arms. However, they have also been known to have as little as 7 and as many as 13. Although this isn’t the most interesting fact about them. They’re actually one of the few cannibalistic starfish species, meaning they sometimes eat other starfish.

Spiny starfish (Marthasterias glacialis)

 As the name might suggest, spiny starfish are covered in tiny spines. To be exact, they have three rows of spines on each of their five arms. This, combined with their unique grey-green colourings, makes them an easy species to spot.

Pin cushion sea star (Culcita novaeguineae)

Pin cushion sea stars have much shorter arms than many other starfish species. Resembling a pincushion rather than a star, this starfish will often have a patchy appearance with multiple base colours across its body.

Want to know more about starfish?

Starfish are fascinating creatures with plenty of facts to learn about. Here are just a few of our favourites:

• They’re not fish: Technically speaking, Starfish aren’t fish – they aren’t even related! Actual relatives include sea cucumbers, sand dollars and sea urchins since they’re part of a group of invertebrates.
• They have long lives: Their lifespans are long compared to other small invertebrates, and they can live for around 35 years. The larger the species, the longer they tend to live.
• Limb regeneration: These star-shaped creatures can regenerate their own arms. So, if you spot a starfish with one arm smaller than the others, it means they’re in the regrowth process. Some tropical species of starfish can even form a completely new starfish from just a part of a damaged limb, although this can take up to a year to happen.
• They lack brains and blood: Instead of blood pumping nutrients around their bodies, starfish can use seawater to do the same thing. The great thing is, they’re never going to run out!

If you’d still like to learn more, you can delve deeper into the lives of these incredible invertebrates with our handy blog.

If you’d like to come and meet our collection of starfish and other exciting creatures at Tynemouth Aquarium, book your tickets today.