ECHINODERMATA: STARFISH AND SEA URCHINS
pink short spined star: Pisaster brevispinus
Did you know that sand dollars are actually animals? Sand dollars, along with starfish and sea urchins, make up the phylum...
...Echinodermata. All these animals have radial symmetry, meaning they can be cut in half in any direction to reveal the same thing on either side! No echinoderm is complete without an exoskeleton, bumpy or spiny epidermis, mouth, stomach, intestines, nerve ring surrounding the mouth, and cells sensitive to light and touch. They do not have brains or heads. A water vascular system is used by echinoderms for movement, exchange of gases, capturing food, and releasing waste. It is a system of canals filled with water. The animal moves by extending and retracting its tube feet, which are attached to the canals. This phylum can reproduce sexually by releasing egg and sperm into the water or asexually by regeneration. I find it incredibly interesting that an echinoderm embryo develops in the same way a backboned animal embryo develops, causing scientists to say that echinoderms more closely resemble backboned animals than any other invertebrate. Check out the goose foot starfish by clicking the button!