Zoology Lab 106 Echinodermata
Zoology Lab 106 Echinodermata Bio 106-016
Kutztown University of Pennsylvania
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This 4 page Class Notes was uploaded by Dallas Bowe on Wednesday March 23, 2016. The Class Notes belongs to Bio 106-016 at Kutztown University of Pennsylvania taught by Dr. Nancy Butler in Spring 2016. Since its upload, it has received 21 views. For similar materials see Zoology Lab in Biology at Kutztown University of Pennsylvania.
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Date Created: 03/23/16
Chapter 13 Echinoderms Kingdom: Animalia Phylum: Echinodermata Deuterostomes o Anus develops 1st opening in blastopore o Indeterminant development o Radial cleavage Marine Symmetry o Pentaradial symmetry in adults o Bilateral symmetry in juveniles Nervous system o No cephalization No head or brain No centralization of nervous system o Possess a nerve ring with nerves radiating out evenly around body Body o Endoskeleton Composed of calcium carbonate ossicles Covered by cuticle o Dermal branchiae (skin gills) thin outpockets distributed along the epidermis surface that allow gas exchange to occur between the outer sea water and inner coelomic fluid No respiratory or circulatory systems o Diffusion through coelom Water vascular system o Uses seawater to generate hydraulic pressure that powers the tube feet for locomotion and for capturing prey Class and Characteristics Representative Animals Crinoidea Stalk present and attached to aboral surface; mouth and anus both ~ 625 species present on oral surface, branched arms with feathery pinnules; Sea lilies, feather madreporite absent stars Ophiuroidea Long, slender arms distinct from central disc; tube feet lack suckers ~ 2,100 species and are not used for locomotion; no ambulacral grooves; Brittle stars madreporite on oral surface Echinoidea Body spherical or discshaped and without arms; endoskeleton ~ 950 species plates fused to form test; tube feet with suckers; welldeveloped, Sea urchins, sand movable spines dollars Asteroidea Broad arms indistinct from central disc; tube feet with suckers ~1,600 species present in ambulacral grooves; anus and madreporite present on Sea Stars aboral surface Holothuroidea Body soft and cylindrical and without arms; spines absent; tube feet ~ 1, 150 species with suckers; mouth surrounded by branching tentacles; madreporite Sea cucumbers internal Sea Stars Kingdom: Animalia Phylum: Echinodermata Class: Asteroidea Genus: Asterias Feeding o Carnivorous predators Slowmoving; stalk prey o Mouth → Esophagus → Cardiac stomach → Pyloric stomach → pairs of Digestive glands extend into each arm and connect to pyloric stomach by pyloric ducts → food passes aborally in intestine → branched rectal ceca → undigested waste is eliminated through anus I.e. Sea star everts its cardiac stomach through mouth and wedges it intp slit of bivalve’s shell; digestive enzymes from digestive glands pour into body, partially digesting it; pulled into pyloric stomach through cardiac stomach where digestion continues; cardiac stomach is pulled back into the coelomic cavity Body o Undersides of arms are covered with tube feet, bearing suckers used for locomotion and prey capture Reproduction o Dioecious o No external features to distinguish sexes o Fertilization is external Males and females must coordinate the timing of reproductive efforts to ensure the fertilization of eggs Water vascular system o Consists of a series of internal canals that branch from a centralized ring canal → terminate into hundreds of tube feet that line the ambulacral grooves along the oral surfaces of the arms o Water enter through madreporite and kept under pressure by muscular contractions (affects all behaviors) → tube feet connect to ampullae to contain water Muscles o Small valves on ambulacral are closed = contraction of muscles in ampullae force water into tube foot to elongate o Postural muscles in tube foot = lateral movements o Contractions of the retractor muscles in tube foot = shortening of tube foot and water forced back into the ampulla External Anatomy of Asterias Structure Function Spines Calcareous projection and support Pedicellariae Pincerlike structures believed to kill small organisms that might settle on body surface, thus keeping the epidermis free of parasites and algae Dermal Gas exchange and excretion through simple diffusion branchiae Mouth External opening to cardiac stomach (through a short esophagus) Anus Regulates egestion of undigested food (feces) from the body Madreporite Porous entrance to the water vascular system that serves as both pressure regulator and simple filter Ambulacral Radiate from the mouth to the tip of each arm and house the tube feet grooves Tube feet Locomotion and prey capture Internal Anatomy of Asterias Structure Function Cardiac stomach Can be everted through the mouth to envelope prey; site of initiation of digestion Pyloric stomach Receives secretion of digestive glands for chemical digestion Digestive glands Secrete digestive enzymes for breakdown of food; play a major role in absorption and storage of food materials Rectal ceca Small, branched “trees” that increase the surface area of the intestine for more efficient nutrient absorption Gonads Produce gametes for reproduction Ring canal Portion of water vascular system encircling the mouth Radial canals Portions of water vascular system emanating from the ring canal and leading into each arm of the sea star Stone canal Portion of water vascular system leading from the madreporite to the ring canal Madreporite Porous entrance to the water vascular system that serves as both pressure regulator and simple filter Ampullae Provide hydraulic pressure for movement of the tube feet Ossicles of endoskeleton Support