Transcript Document
Ecinoderm • Kingdom: Animalia • Phylum: Enchinoderm Body Plan • Levels of Organization: Specialized Cells, Tissues, and Organs • Body Symmetry: Radial (as adults) • Germ Layers: Three • Body Cavity: True Coelom • Embryological Development: Deuterostome • Segmentation: Absent • Cephalization: Absent Characteristics • Regeneration • All echinoderms exhibit fivefold radial symmetry in portions of their body at some stage of life • Mesodermal skeleton composed of calcareous plates or ossicles Characteristics • Echinoderms possess a unique water vascular system. – a network of fluid-filled canals derived from the coeom • Function in: – gas exchange – feeding – sensory reception – locomotion Feeding • Mouth on oral surface (bottom / ventral) • Anus on aboral surface (top / dorsal) http://www.youtube.com/watch?v=HG17TsgV_qI Respiration, Circulation, Excretion • Circulation - A Echinoderm has water pumped through its body as part of its very simple circulation system. • Respiration - A Echinoderm uses some of the bumps or spines on its surface to take in oxygen. It has a gill structure to take in the oxygen. It has a poorly developed respiratory system. Response • Water is pushed in and out of the system enabling the echinoderm to move • Path of the water: – Madreporite Stone Canal Ring Canal Radial Canal Ampulla Tube Feet Reproduction • Can reproduce asexually through regeneration. • Sexually: Fertilization is external – Few species are hermaphroditic – Starfish have either 2 testes or 2 ovaries per arm Habitat • Marine waters – typically in shallow environments. Classes • The 5 living classes of echinoderms are – Asteroidea (sea stars) – Crinoidea (sea lillies) – Echinoidea (sea urchins and sand dollars) – Holothuroidea (sea cucumbers) – Ophiuroidea (brittle stars and basket stars) Class Asteroidea • Sea Stars • Have five arms radiating from a central disc – Mouth (underside) – Anus (topside) – Madreporite (topside) • Can regenerate a broken limb or even an entire body – Only if part of the central disc is intact • Can take up to a year Class Ophiuroidea • Tube feet lack suckers and ampulla • 2000 species of brittle stars • Usually concealed in sand or under objects • Some live in sponges or other colonial organisms • Only 5 arms that are usually highly branched from central disk • Can crawl/cling • Predators, scavengers, or suspension feeders • Flexible arms bear suckerless podia that secrete mucus to entrap food and transport it to mouth Class Crinoidea • Most primitive • Feather like arms used for suspension feeding – Plankton • Tube feet trap planktonic organism • Cilia in ambulacral grooves carry food to mouth • Attach to substrate with stalk • Sessile sea lily • Cup-like body attached to stalk • Can bend stalk and flex/extend arms Class Echinoidea • Shell (test) encloses body – Ossicles form plates • No arms • Long spines – Movement – Venom • 1000 species of sea urchins/sand dollars • Movable spines and podia surround body; used for locomotion • Herbivorous, detrivorous, suspension feed, a few predators • Unique feeding apparatus called Aristotle’s lantern • Hard plates and muscles just inside mouth • Possesses 5 calcareous teeth • Teeth protract to scrape algae off rocks or tear chunks of kelp http://www.youtube.com/watch?v=D3W4OCnHyCs Class Holothuroidea • Soft body with reduced ossicles • Tentacles near mouth • Respiratory tree – Breaths through anus • 1150 species of sea cucumbers • Mucus-covered oral tentacles trap on plankton or ingest sand organic matter • Gut modified to produce respiratory trees used for gas exchange • Expel portions of these trees as defense mechanism; regenerate http://www.youtube.com/watch?v=wXf_YodWw40