Species Spotlight: The Stars of the Sea
Even though this animal is commonly called the starfish, did you know it’s not actually a fish? Instead, it’s classified as an echinoderm and the more appropriate name for it is sea star.
Echinoderms are “spiny skinned” marine invertebrates that exhibit radial symmetry and even have the ability to regenerate body parts! To classify as a fish, an animal would need vertebrae and spinal cord, a brain, fins, and scales - none of which sea stars have.
The sea star is possibly one of the most recognizable and iconic of all marine species, so this week we’re taking a closer look at one of our local species of sea star: the Eastern sea star!
Eastern sea star
Bottom view of sea star
Sea star preparing its lunch
Sea star attached to tank wall
Eastern Sea Star
Also Known as Forbes sea star, Common sea star
Scientific Name: Asterias forbesi
Identification: About 5 inches in diameter on average with 5 arms radiating from a central disc. Each arm has a single eyespot on the tip with hundreds of tiny tube feet underneath. Rough, almost spiky skin that varies in color from reddish, to orange, brown, or even sometimes shades of purple! The orange dot on top is the madreporite, this is where water enters the sea star’s body for use in its water vascular system.
Diet: Primarily bivalve mollusks such as oysters, clams, and mussels. May also feed on small snails and other marine invertebrates.
Habitat: Found in the low intertidal zone or below it, in rocky areas or oyster and mussel beds.
Find this Species: This is a tricky species to find and unfortunately often collected as a souvenir. If you want to see these unique animals up close, we recommend visiting your local aquarium or marine science education center! And if you’re lucky enough to spot one while you’re out enjoying coastal environments this summer, be kind enough not to disturb it.
Interesting Facts: A sea star’s digestion starts externally! Once a sea star positions its mouth over its prey of choice, it releases its stomach into the shell of its prey. Digestive enzymes then start to break down its prey until it’s ready to be engulfed.
Sea stars, like all echinoderms, can regrow lost body parts! As a method of self-defense, sea stars are capable of self-amputation. When a predator has hold of an arm, a sea star can drop that arm to escape. Regeneration can take months to years to complete.
While sea stars don’t have true eyes as we do, their eyespots are photosensitive and allow them to sense shadows and shapes as they navigate their environment. If you look carefully, you can see their eyespots! A single eyespot is located on the tip of each arm and usually appears red or black in coloration.
Sea stars do not have blood! In fact, the madreporite filters water as it enters their water vascular system. This system allows them to change the water pressure within their body and move their tube feet!
Cousins of Sea Stars
Did you know that Long Island is home to several echinoderms? This includes sand dollars, sea cucumbers, sea urchins, and brittle stars! All of these animals can be considered “cousins” of sea stars since they belong to the same phylum.
Echinoderms are unable to control the composition of their body’s saline fluids and, therefore, don’t often survive drastic changes in salinity. They rely on healthy water bodies to survive, so let’s keep giving back to our bays to keep these iconic marine species around!
