Duy's AP BIO Blog: BOW Starfish

The scientific names for starfishes are called echinoderms. Starfish are marine invertebrates. They have a central point along with 5 or more arms. Echinoderms have tube feet with suction pads. They evolved from bilateral symmetrical animals. Echinoderms have mesodermal skeletons. The left side of their body tends to grow symmetrically in a pentagon like shape. Starfish preys on clams and oysters. They are also filter feeders. Their body wall consists of three layers. The first outer layer is a single layer of cells that covers the entire starfish. The third layer are made up of ciliated cells that separates the starfish's guts from its skin. The middle layer is a thick layer called the dermis. It is made up of connective tissue and contains the exoskeleton. The exoskeleton supports the spines, warts, and tubercles that are found on the echinoderm surface.
Echinoderms has contact with the external world through its water vascular system including the tube feet. The water vascular system starts with an opening to the external environment called a madreporite. Then continues the stone canals that leads to the ring canal that has five longitudinal canals branching off from it into each of the arms. In the Crinoidea, it has a U-shaped guy with the mouth and the anus being on the same surface. Echinoderms have a sub-epidermal never net running all over their body. Many Echinoderms use their tube feet as organs for gaseous exchange, but others such as the Ophiuroidea and the Holothuroidea have additional special sites or organs of respiration.