Echinodermata is a phylum of species that share similarities. The species that fall under this phylum include starfish, brittle stars, sea urchins, sand dollars, sea lilies, feather stars, and sea cucumbers. Their shared characteristics is that they all have radial symmetry and spine skin. Additionally there body is built onto their original larva body. They go through a radical metamorphosis which results in there body being drastically different. They also have a nerve ring, which acts as their brain, the nerves flow through there water vascular system.
However the respiratory system is different for for starfish, sea cucumbers, and sea urchins. Starfish take in water with there tube feet and use gills to regulate the water. Urchins have five sets of gills near there mouth, they regulate their breathing by the current and as they move. If they’re beginning to run low on oxygen they will use either their muscles to pump the water or breath through tubed feet like the starfish. A sea cucumber breathes through respiratory trees located inside their anus.
The digestive system of echinoderms are simple and complete, some have extra stomachs. In terms of what they eat and their means of eating is different for each of them. Sea urchins are omnivores they eat seaweed, algae, and small organisms. They are eaten by sharks, bony fish, and crabs the same goes for all echinoderms. Starfish are predators that prey on small food at the ocean floor. They protrude their stomach out of there body around the prey, slowly dissolving it. Sea cucumbers are scavengers eating waste on the ocean floor.
Echinoderms also have positive effects on the marine environment. By eating seaweed urchins keep it from over growing and causing damage. Starfish prevent algae from overgrowing and causing oxygen related issues. Sea cucumbers and sand dollars provide increased oxygen on the ocean floor for other animals.
Echinoderms also have value to us, and we use them in a variety of different ways. Sea cucumbers are often used as soap in certain parts of the world. The gonads of urchins are used as food both cooked and raw, in some parts of the world. Holothurin which is a toxin that comes from sea cucumbers is not harmful to us. In which can be used as a way of slowing growth in tumors. The eggs and sperm of urchins and starfish are often used as research for biology labs.