By Irene…

*Starfish !!!

STARFISH Starfish(sea stars) are Echinoderms of the Class

Asteroidea which means they are invertebrate. They all live in the ocean, on the sea floor. Some live in deep water, others in the shallow water and some live in the intertidal zone, between high and low tide. Starfish can have five or more arms and can be quite large. Sunflower starfish is the largest: fully grown, its arm-span is about a metre. This is a bit bigger than the famous Crown-of-thorn starfish, which lives on coral polyps.

*More about starfish!!!

Although starfish are invertebrates, they do have a kind of skeleton. The body of starfish are composed cal-cium carbonate plates, known as ‘ossicles’. These form the endoskeleton, which takes on a variety of forms such as spines and granules. Starfish has primitive nervous system, but not a brain. They also don’t have blood, instead they use sea water to pump things around their body. There are 1500 dif -ferent species of starfish. Most of them are predators. They eat mussels, clams, and other bivalves. Occasion-ally they catch small fish.

some pic-tures of

starfish!!!

*The shells of brachiopods and bivalves are held together by strong muscles. What the starfish does is clamp hold of them on either side with its tube feet, and apply a steady pull. The starfish, with its mus-cles and hydraulic system, can pull for much longer than any bivalve muscle can withstand. Apparently, ten minutes are usually enough to open the shell a bit. Then the starfish slips its stomach inside the shell. The stomach can get through a slot as narrow as 0.1mm. The starfish then dissolves the mollusc where it lives, absorbing the nutrients. This digestion process takes much longer than opening the shell, perhaps a couple of days.

*Feeding Method!!!

*Symmetry~* Most starfish have five arms, called rays that come out

from a center circle (disk). If a starfish has more than five rays, it will often have rays in multiples of five; there could be 10, 15, 20, or even 30 rays on one starfish. This is called pentameral (five-fold) symmetry.

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*I Hope You En-joyed!!!