BIOL 1604 Lecture Notes - Lecture 17: Detritivore, Keystone Species, Gonad
Document Summary
Formation of mouth form secondary opening in the embryo. Larval stages have bilateral symmetry, most adults have pentaradial symmetry. Complete digestive system no excretory organs. Ambulacrum: a band from which tube feet (podia) project. Symmetry: adults pentaradial, larvae bilateral. Pedicellariae and spines: aboral surface usually rough and spiny, frequently present pincher like pedicellariae. Madreporite: a calcareous sieve leading to the water-vascular system: water vascular system is coelomic compartment made of series of canals and specialized tube feet that forms a hydraulic system with dermal ossicles. Digestion mostly extracellular in the pyloric ceca. Lack of brain and distinct ganglia but has nerve ring and radial nerves. Reproduction: most dioecious with external fertilization, regeneration of lost parts. Development: free swimming larva bipinnaria, larva brachiolaria undergoes metamorphosis. Endoskeletal test or shell formed by dermal ossicles. Compact skeleton of 10 double rows of plates that bear moveable, stiff spines. The oral surface has expanded to the aboral side.
