Whether you're diving in the Caribbean, or bravely setting out on an underwater polar expedition, island travelers have a very good chance of spotting a starfish. The starfish or "sea star" has always been one of my favorites sea creatures. Not long ago in Guadeloupe Zickie and I came across huge orange starfish, larger than his hand. We picked them up, inspected them closely, then set them back gently on the sandy ocean floor. They are marvels of nature.
(The starry five-armed wonder. Photo by AnntiTNissinen, Flickr.)
But what do we know about starfish? Well, one fact I learned as a child is that they're very sensitive to the quality of their surrounding water (like all echinoderms). I tried to keep five alive for a science fair project, and despite my best efforts at maintaining a salt water aquarium, the poor starfish died. These days, I'm happy to appreciate them in their natural habitats.
Here are a few details about starfish that you may or may not already know:
1. Starfish inhabit all the world's oceans, and they have adapted over millennia to waters that range from the tropical to the polar. Their ability to adapt doesn't stop there: starfish live at depths of 20,000 feet below the sea's surface, and well as in the shallows.
(A scarlet colored starfish off Tenerife. Photo by Philippe Guillaume, Flickr.)
2. Although most have five arms, some starfish have more. All starfish -- all 1500 species of them -- are marine invertebrates. An invertebrate does not have a central spinal column. Their mouths lie in their central disc (what we might think of as their underside). They propel themselves over the sand and across corals by means of their many tube feet.
(Starfish can come in many colors. Photo by Steven Gessner, Flickr.)
3. Some starfish, particularly the larger species, have surprisingly long lives. One type, the Leptasterias hexactis, has a lifespan of about 10 years, while another, Pisaster ochraceus, has lived as long as 34 years. The starfish's ability to shed an arm in self-defense, and then regenerate it, must contribute to its longevity.
(A starfish slowly climbs over corals. Photo by Razvan Marescu, Flickr.)
The more I read about starfish, the more I realize what curious and unusual beings they are. Some starfish can reproduce by dividing themselves in two! Other starfish can extrude their stomachs outside of their bodies. (Aren't you glad human beings don't have that ability?) Externally, a starfish might look very simple, a five-armed thing that creeps along the sea bottom and lives a rather quiet life. But, as with many marine animals, their complex biological systems -- along with their beauty -- make them true marvels of nature.
(A starfish off Thailand. Photo by Thomas Quine, Flickr.)
I hope you enjoyed the Island Runaways' brief look into these brilliant stars of the sea. Do you have a sea creature you'd like featured in your Tropical Reef/Island Nature series? If so, let us know on our Guest Island Experts page. We'd be glad to hear from you!