Stars of the Sea
They are known as the stars of the sea, but starfish can no longer be found on our beaches because of land reclamation and pollutive human activities along the coasts. Instead, they are displayed at the oceanarium at Underwater World, or living in their natural habitat at Chek Jawa (Pulau Ubin).
Sea Star
The starfish (sea star) is not a type of fish. It belongs to an animal class called echinodermata, which includes sea urchins, feather stars and sea cucumbers.
There are 1 800 species of starfish living in the Earth's oceans, but the greatest variety of starfish is found in the tropical Indo-Pacific, tropical East Pacific, the cold-temperate North Pacific and Australia. Their habitats range from tropical coral reefs, kelp forests to deep-sea floor.
Not Five-Star
How do you draw a starfish? Certainly not in the shape of a five-rayed star! Starfish do not always have five arms; some have up to forty arms, and there are some with fewer than five arms. In fact, starfish belonging to the same species can have different numbers of arms.
Starfish have disc-like bodies, and their mouths are located on the underside of their bodies. The mouth leads to a bag-like stomach. The stomach has grooves that extend from the mouth to the tip of each arm. The small tube-like feet on each arm help the starfish to walk. Some species of starfish have suction cups on the arms as well. Each of the arms has an eye-spot that helps the starfish to sense the presence of light.
Diet of a starfish
Most starfish are predators. They hunt for mussels, clams, oysters, or any animal slow enough to be preyed upon. Some species of starfish feed on decomposed animals and plant materials, or sea sponges, suspended particles and planktons. Once the starfish finds its prey, it will attach itself to its prey. It will then turn its stomach inside out and place its stomach near the prey. The stomach will then digest the animal. Once digested, the starfish sucks the stomach back into its body and the digested substance is sucked up through one of its arms.
Moving Along
Starfish, surprisingly, are very mobile animals and can travel long distances within a fairly short time. The rate at which an adult starfish can move depends on the area it is attempting to cross. Over sand, an adult crown-of-thorns starfish can travel at a speed of 20 meter per hour, while over areas where there are many live coral, it may travel at a speed of 0.25 meter per hour. Younger starfish can only move at rates varying from 0.06 to 4 meter per hour. It has been recorded that a whole school of starfish travels approximately 580 meters within a single week.
Strange creatures
Starfish are indeed strange creatures. They do not have a “front” or a “back”, thus they can move in any direction without turning. To move around or to cling to rocks, starfish do not use their hundreds of tiny “legs”. Instead, they use a complex hydraulic system. Try prying a starfish off a rock, and you will know how effective its hydraulic system really is. If you managed to pry a starfish off a rock, you will notice that it immediately stiffen itself.
Starfish are definitely unique. It is sad that our East Coast, Pasir Ris and Changi beaches are not strewn with these unique sea stars. However, just in case you find a starfish lying on the beach one day, thank your lucky stars and quickly put the starfish back into the water because starfish dry out very fast once they are out of water. If you see one in a tidal pool instead, say hello and remember to put it back into the water, alright?
Starry Facts about Starfish:
- Starfish do not have a brain.
- To escape predators, starfish may deliberately detach their arms from their body. This serves to distract the predators and give the starfish time to escape. Later on, new arms will grow in place of the detached ones.
- If a starfish is being cut up, the detached part of the starfish can eventually grow into an independent starfish.
- Starfish can force open the shells of clams and mussels using their arms and force their stomachs into the shells.
- Starfish can change colours.
The smallest starfish –Brittle starfish– is only 1-2 cm wide, and the largest –Sunflower starfish– is more than 60 cm wide.