| |
Starfish
Sunday, 24 December 2006 - 8:20 AM SL Time | | |
Sea stars or starfish are marine invertebrates. There are about 1,800 living species of sea star, and they occur in all of the Earth`s oceans. The greatest varieties of sea stars are found in the tropical Indo-Pacific.
Sea stars do not have movable skeletons, but instead possess a hydraulic water vascular system. The water vascular system has many projections called tube feet, located on the ventral face of the sea star`s arms, which function in locomotion and aid with feeding.
Sea stars are composed of a central disc from which arms sprout in radial symmetry. Most starfish have five arms, however some have more or less; in fact some starfish can have different numbers of arms even within one species.
The mouth is located underneath the sea star on the oral or ventral surface, while the anus is located on the top of the animal.
Most sea star species are generalist predators, some eating bivalves like mussels, clams, and oysters; or any animal slow enough to be unable to evade the attack.
Sea stars are capable of both intimacyual and aintimacyual reproduction. Individual sea stars are male or female. Fertilization takes place externally, both male and female releasing their gametes into the environment.
|
Source(s)
Wikipedia / Webshots |
|
