You may see many different type of sea stars if you go snorkeling – these interesting creatures can be found in all the world ocean’s from tropics to the cold waters. We think it is time to know more about them and so here are some facts and infos for you.
Sea stars or starfish?
Many people know sea stars as starfish, but they are not really fish. They belongs to the “invertebrates”, do not have backbones like sea urchins or sand dollars. Marine biologists know more than 1500 different species.
Sea stars are absolutely salt water fanatics – they don’t live in freshwater. They can be found on rocky shores, in sea grass, kelp beds, coral reefs, tidal pools and also in sand (some live as deep as 6000 meters – 20.000 ft) They usually live a lonely life – but sometimes congregate in larger groups during certain times of the year to feed.
They have a long life – can live up to 35 years. Their normal size is between 12-24 cm (4.7-9.4 in) and weight up to 5 kg (11 lbs).They have no brain and no blood – their nervous system is spread through the arms, and filtered sea water is circulating in their body as”blood”.
Most of them have five arms, but some species can grow 10, 20 or even 50 arms, unbelievable, isn’t it? These arms are covered with pincerlike organs which help the sea stars to slowly move on the sea floor. On the tips of the arms they have eyespots. These eyespots are important to help them find food. They eat usually mollusks (clams, snails or oysters). When a sea star eats it extends its stomach thorugh the mouth and the enzymes from the stomach digest its prey. When the enzymes digested the prey the stomach withdraws back into the body.Their calcified skin protect them from predators and also helps to camouflage – some species make it different and wear vibrant colors to scare off attackers.
You can call them survivors – they have the ability to regenerate limbs or some species even their entire body just from a portion of a severed limb!
Weird habits – sea star on the menu
Sea stars are sometimes eaten in China, Japan and in Micronesia – In the Indonesian achipelago the people cut them up, squeeze out their “blood” and cook them with tamarind leaves. After they remove the outer skin and cook again in coconut milk. But on other places on the world they are only occasianally used as food – they contains saponins which give an unpleasant tast and some species also contain poisonous tetrodotoxins.It is much more common than they are sold as souvenirs. We do no think it is a nice thing – take photos of them in their natural environment and go home with your memories! In the early to the mid 20th century trade and collection have reduced their numbers in the Caribbean and along the coast of the West Indies so some species were listed as endangered – Although the collection became illegal it is still sold on several places…
Sea stars have key figure in respective marine communities – their ability to adapt to different ecosystems, large sizes and diverse diet make them ecologically important. Some study confirmed that their removel from shorlines resulted in lower species diversity while certain mussels started to increase in number dramatically.However they have sometimes negative effect on ecosystems: the crown-of-thorns sea star outbreaks caused serious damage on the coral reefs in Australia. In French Polynesia, migratory sea star species damaged drastically the reef – the coral cover dropped from 50 % to 5 % in three years. Some species are among the world’s 100 worst invasive species.Unfortunately we often see photos on Instagram or on the web that people hold a sea star in their hand or take them out of the water – Please do not do this! They are living creatures and as responsible snorkelers we should protect the marine life – you may watch them but do not disturb their life by touching or moving them!
Sources : wikipedia.org , nationalgeographic.com