BZ 110 Lecture Notes - Lecture 5: Gonopore, Sea Cucumber, Body Cavity
Document Summary
Rign canal opens to outside via stone canal and madreporite. Often suction cup at distal end (blunt or pointed) Nervous system consisting of nerve net, nerve ring, and radial nerves. Body parts are arranged in fives around an oral aboral axis. Arrangement of the body in fives means skeletal joints are not directly opposite one another. This arrangement may make the skeleton stronger than if joints were opposite one another. Entire sea star from portion of central disk. Basket stars (gorgonocephalus arcticus) and brittle stars (ophiopholis aculeata) Arms long, sharply set off from central disk (highly branched in basket stars) Muscles and articulating ossicles produce snake like movements of arms. Water vascular system is not used in locomotion. Wave arms and trap plankton on mucus covered tube feet. Eggs may be retained and fertilized within bursa or released for external fertilization. Ophiopluteus (larva) is planktonic and metamorphoses to adult. Sand dollars and heart urchins-sand or mud just below surface.
