Starfish are at the top of most children’s (and many adults’) rock pooling wish lists. If you take time to look under rocks and overhangs, there’s a good chance you’ll find one.
Starfish aren’t fish, of course. They are members of the echinoderm family, together with urchins and sea cucumbers. Like all other sea creatures, sea stars need to stay wet and cool so keep them in water and return them quickly to where you found them.
Identify your starfish here…
(Starfish can lose and re-grow their arms, so the number given is a guide only!)
Does your starfish have five stumpy arms and a puffy centre? If so, you have a cushion star. These are small starfish that fit easily in the palm of your hand. Despite their name, they feel firm to the touch. They move around on tiny tentacle feet – turn yours over to have a look.
Is the back of your starfish covered in rows of large pale spines? You have a Spiny starfish. When fully grown these sea stars are often pale purple or blue, but can also be grey or almost white. These are the largest starfish on the shore.
If your starfish has five arms that taper towards the ends and a scattering of spines, you have a Common starfish. This species is typically a vivid orange colour, although it can be brown or purple. It doesn’t grow as large as the spiny starfish.
As you’d expect, these starfish have seven arms. They are bright orange and have a much less spiny look than the Common starfish. The tentacle feet on the underside are especially long in this species. Keep it wet and turn it over to watch the feet come out. You’ll find them buried in sand.
If your starfish has a fringe of sharp, tooth-like spines all around the edges of its arms, you have a Sand star. You can find them buried on some sandy beaches, but you’re most likely to see them washed up when they’ve been dislodged by stormy weather.
Unlike all the above species, your starfish doesn’t have tentacle feet on its underside. It walks around on its long, fragile arms, which are connected to a central disc. Put them in sea water to watch them unfurl and move around. Brittle stars need to be handled very carefully as they easily shed their arms.
The two most common species on the shore are Ophiothrix fragilis, which has legs that look hairy and stripey, and Amphipholis squamata which is so small it will fit on your thumb nail, curls up when disturbed and looks pale.
Is it something else?There are other species of starfish less commonly seen in the Cornish rock pools. If you’re having any trouble identifying your starfish please do get in touch.
Don’t forget to share starfish photos on my Facebook page.
Discover the secret world of starfish and other rock pool creatures with my book Rock Pool: Extraordinary Encounters Between the Tides.
Have your own beach adventures and see the underwater world as never before with my hands-on children’s activity book, Beach Explorer: 50 Things to See and Discover.