Not much, it turns out. The most common sea star in the North Atlantic (and the waters around Star Island) derives its name from being just that: the common sea star. Otherwise known as Asterias rubens for you scientists. You’ve likely seen them many times in the marine lab over the years.
So what, then, about the other ubiquitous species the Northern sea star or Asterias vulgaris? Turns out scientists have long ago concluded they are the same species. This two-named sea star eats bivalves (a favorite prey item is the blue mussel) and gastropods. They also eat crustaceans and worms. They act both as active predators and scavengers.
P.S. We stopped calling them star fish a long time ago since they actually aren’t much like fish. They do not have gills, scales, or fins like fish do and they move quite differently from fish. While fish propel themselves with their tails, sea stars have tiny tube feet to help them move along.
Another common species in the North Atlantic, around Star, is the Forbes seastar or Asterias forbesi.
A few fun facts on seastars to answer the common questions we get in the lab:
1) Sea stars have eyes: While they can’t see as well as we do, sea stars have an eye spot at the end of each arm. This is a very simple eye that looks like a red spot. The eye doesn’t see much detail but it can sense light and dark.
2) Instead of blood, sea stars have a water vascular system in which the sea star pumps sea water through its sieve plate called a madreporite (or spot where the star draws salt water into its water vascular system). Muscles within the tube feet can also extend and retract these spots.
3) Sea stars don’t use gills or lungs to breathe. They rely on diffusion across surfaces in their body. For example, most oxygen is taken up from water that passes over their tube feet or madereporite which is also where they excrete the waste of respiration.
There are actually thousands of species of sea stars, which are a part of the echinoderm family. Below are pictures of a few of the most unique. You can find more of these pictures along with descriptions of the 13 coolest with our friends at The Mother Nature Network.