This morning I received a nice picture of starfishes from a Facebookfriend. She lives in the Philippines. I like to see starfishes, they’re amazing. This ones (first photo) seems to smile. Sea stars (in Dutch: zeesterren) or starfishes are echinoderms belonging to the class Asteroidea.
A copple of years ago (2008) I visited the famous Monterey Bay Aquarium at the Californian westcoast. I saw living starfishes moving in the water! Amazing. The names “starfish” and “sea star” essentially refer to members of this class. However, common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as “brittle stars” or “basket stars”. About 1,500 living species of starfish occur on the seabed in all the world’s oceans, from the tropics to subzero polar waters. They are found from the intertidal zone down to abyssal depths, 6,000 m (20,000 ft) below the surface. Starfish are among the most familiar of marine invertebrates. They typically have a central disc and five arms, though some species have more than this. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. Many species are brightly coloured in various shades of red ( see picture) or orange, while others are blue, grey or brown. Starfish have tube feet operated by a ingenious hydraulic system and a mouth at the centre of the oral or lower surface. This sea star is a carnivore and feeds on molluscs, which it catches with its arms and then takes to the mouth. They are opportunistic feeders and are mostly predators on benthic invertebrates. Several species having specialized feeding behaviours including eversion of their stomachs and suspension feeding. They have very complex life cycles and can reproduce both sexually and asexually. Most can regenrate damaged parts or lost arms and they can shed arms as a means of defence. The Asteroidea occupy several significant ecological roles. Starfish, such as the ochre sea star (Pisaster ochraceus) and the reef sea star (Stichaster australis), have become widely known as examples of the keystone species concept in ecology.
The fossil record for starfish is ancient, dating back to the Ordovician around 450 million years ago (The Ordovician, named after the Celtic tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute) , but it is rather poor, as starfish tend to disintegrate after death. Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate.
Starfish is also popular for collecting purposes. With their appealing symmetrical shape, starfish have played a part in literature, legend, design and popular culture. They are sometimes collected as curios, used in design or as logos, and in some cultures, despite possible toxicity, they are eaten.
© Marius van Westland, January 18th, 2014
I appreciate your comments
Photo 1: received from T.L.H., Philippines
Starfishes in Biak na Bato National Park
Photo 2: Astropecten aranciacus ossicles
Photo 3: Girls found starfishes in Biak na Bato National Park
(used with permission)
Photo 4: internet
Read more at Wikipedia: Starfish (EN)
Lees in het Nederlands/Read in Dutch: Zeesterren