Phylum Echinodermata - MHHS 2016-2017 - Phylum Echinodermata spiny skinned or hedgehog skin sea stars (starfish), ... locomotion (most mobile echinoderm!)

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  • Echinoderms Phylum Echinodermata

  • spiny skinned or hedgehog skin

    sea stars (starfish), sea urchins, sea cucumbers

    6000 species

    radial symmetry in 2o development

    bilateral symmetry in larva

  • http://www.biologyreference.com/Dn-Ep/Echinoderm.html

  • most have pentamerous radial symmetry = based on 5 parts

    live on ocean bottom slow bottom crawlers

    have no head

    no anterior or posterior side oral

    and aboral

    complete digestive tract

    internal endoskeleton secreted w/in tissues may be covered by a thin layer of ciliated tissues

  • Digestion mostly carnivorous

    feeds by extending/everting part of stomach inside out thru mouth secreting digestive enzymes carries food back into mouth

    guts may be very short (starfish or sea cucumber) or very long (sea urchins)

    longer guts are needed to digest plant particles

    nutrients are transported in fluid called coelemic fluid in the coelem

  • Circulatory system/gas exchange

    O2 is transported via coelemic fluid

    Lacks a true circulatory system

    Gas exchange occurs in small, branched projections of the body wall connected to coelemic cavity

    Sea cucumbers have respiratory trees pair of thin branched tubes

    that are extensions of gut and are suspended in coelem by coelemic fluid they draw in water and

    provide increased surface area for gas exchange

  • Nervous system

    have a nerve net

    coordinates tube feet and spine mvmt.

    no brain

  • Reproduction

    dioecious

    may have 5-10 gonads located in body cavity

    all species spawn at once to better insure fertilization in which eggs and sperm are simply released into water

    fertilized egg develops into plankton as a ciliated larva (bilaterally symm.)

    asexual reproduction by regeneration ability to grow back lost/damaged parts

  • Class Asteroidea

    Sea stars, a.k.a. starfish

    5 arms radiating from a central disk with eyespot at each end that is sensitive to light

    hundreds of tube feet with suckers protrude from oral surface along ambulacral groove

    move in any direction very slowly

  • Class Asteroidea

    have pedicellariae = modified spines that are pincer-like organs used to clean the surface

    have a water vascular system use as others use muscles

    predators of bivalves, snails, barnacles, other slow moving animals

    Ex. Asterias

  • Class Ophiuroidea

    Brittle stars

    2000 species

    very long and flexible arms

    arms move in snake-like motion for locomotion (most mobile echinoderm!)

    tube feet have no suckers and are used for feeding

    feed on organic matter and small animals picked up from the bottom (most are scavengers)

  • Class Ophiuroidea food is picked up by tube feet and

    passed to the mouth

    hide under rocks, coral, or cover up with mud/sand (dont like light!)

    ex. spiny brittle star Ophiothrix angulata found subtidally from Chesapeake Bay to Florida

    Ophioderma brevisipina lives in shallow water from Cape Cod to Florida

  • Class Echinoidea

    Sea urchins and sand dollars

    900 species

    endoskeleton forms a rigid test w/ movable spines and pedicullariae

    possess a water vascular system

    move by spines jointed to sockets in the test and suckers at the tip of each tube foot

    5 rows of ambulacral grooves w/ tube feet extending from pole to pole w/ mouth on the bottom and anus on top

  • Class Echinoidea System of jaw & muscles called

    Aristotles lantern used for biting off algae

    omnivores

    graze on attached or drifting plant material

    ingest encrusting animals (like sponges and bryozoans) and dead organic material

    very common on rocky shores

    when it dies, it leaves behind the test ex. Eucidarias tribuloides - Carolinas to Florida very

    thick and blunt

    ex. Mellita quinquiesperforta - sand dollars found from Cape Hatteras (NC) to Florida yellow-brown in color bring food to mouth as they walk - small particles of food are chewed by dentary apparations - rattles when skeleton is shaken eaten by sea stars, flounder and cod

  • Class Holothiuroidea

    Sea cucumbers

    worm-like no spines - no radial symmetry

    usually lies on one side w/ mouth at one end and anus at the other

    endoskeleton has microscopic calcareous spicules throughout warty skin

    have 5 rows of tube feet extending from mouth to anus

    are deposit feeders

  • Class Holothiuroidea

    tube feet around mouth are branched tentacles that pick up organic matter

    may secrete toxic chemicals or discharge sticky filaments thru anus as defense

    may expel gut and internal organs thru the mouth/anus = evisceration (extending the gut to distract the offender) sea cucumber regrows any lost parts w/in 6 wks. messy but effective

  • Class Holothiuroidea

    ex. Leptosynapta snot sea cucumber no tube feet located all over the whole coast consumes detritus as it burrows

    ex. Sclerodactyla briareus hairy sea cucumber - Cape Cod to Gulf of Mexico covered by slender tube feet

    Japanese cook in soy sauce and ginger in China dry it and is a gourmet delicacy

  • Class Crinoidea

    Feather stars and sea lilies

    Suspension feeders that use outstretched feathery arms to obtain food from water

    600 species

    some are restricted to deep water and attach to bottom (sea lilies)

    come crawl on hard bottoms in shallow water to deep water in tropical Pacific and Indian Oceans (feather stars)

  • Class Crinoidea

    resemble upside down brittle stars w/ ambulacral grooves and mouth upwards

    larger organs are restricted to a small cup-shaped body from which arms radiate

    may have from 5-200 arms w/ possible side branching

    side branches have tiny tube feet that secrete mucus to aid in food catching

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