Starfish

For the first real post I’ve decided to dive right in (excuse the most obvious ever of puns), with a well known and recognizable sea creature: the starfish.

 

The leather sea star, Dermasterias imbricata

 

The starfish, or sea star, is not related to fish at all but is rather part of a group of organisms called echinoderms, which includes several other marine animals such as sea urchins, feather stars, and sea cucumbers. There are over a thousand species of sea star, which can be found in all of the world’s oceans. They are considered invertebrates, which means they do not have a backbone, although they do have a skeleton made of bony plates. Most people recognize  starfish by their five arms, radiating symmetrically outward from a central point; however, some species can grow more than five arms, and even numbering up to forty.  It is both fascinating and fairly common knowledge that some species of starfish have the ability to not only regenerate a new limb if one is removed, but also to regenerate a whole new starfish from said limb.

 

Crown-of-thorns starfish, Acanthaster planci

 

Nine-armed sea star, Luidia senegalensis

While the starfish does have a nervous system, it lacks a brain and complex sensing organs. Starfish also have a circulatory system but do not have any blood: they instead use a  network of tubes filled with filtered sea water. The sea water is used to transport nutrients and oxygen, and even provides hydraulics to move thousands of tiny tube feet located on the arms.

Fun Fact: Most starfish have the ability to consume prey outside of their body. Basically, the sack like cardiac stomach (see diagram) is pushed out through the mouth of the starfish (located at the centre of the main body portion) which then enters the shell of a clam or oyster, where it can begin its process of digestion. Yum!

 

Thanks for stopping by, guys, and I hope you enjoyed my first post!