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Echinodermata PowerPoint PPT Presentation

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Echinodermata. Spiny-Skinned Invertebrates. Domain: Eukarya Kingdom: Animalia Phylum: Echinodermata SubClass : Asteroidea Class: Ophiuroidea Class: Holothuroidea Class: Crinoidea. Sea stars Brittle stars Featherstars Sea urchins Sand dollars Sea cucumbers. Examples .

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Spiny-Skinned Invertebrates


  • Domain: Eukarya

  • Kingdom: Animalia

  • Phylum: Echinodermata

  • SubClass: Asteroidea

  • Class: Ophiuroidea

  • Class: Holothuroidea

  • Class: Crinoidea


  • Sea stars

  • Brittle stars

  • Featherstars

  • Sea urchins

  • Sand dollars

  • Sea cucumbers


Phylum characteristics

  • NO freshwater

  • Live on rocks or ocean floor

  • Radial symmetry- body parts extend from center along 5 spokes “pentaradial”

  • Hard exoskeleton made of calcium carbonate plates

  • No heart, brain, or eyes

  • WHY are they classified as more“advanced” than arthropods?

  • Endoskeleton:

    • Ossicles- calcium plates

Phylum characteristics


  • Mouth is on oral surface (underside) and anus on aboral

Water vascular system defining characteristic

  • Tube feet called “podia”

  • Instead of circulatory system network of water filled canals connected to tube feet

  • Used for gas exchange, feeding, and locomotion

  • When echinoderms move, they force water into the podia (tube feet) which causes them to expand. Muscles attached to podia cause podia to retract. Expansion and contraction cause movement.

  • Tube feet are hydraulically controlled

  • As tube feet press against something, water is withdrawn from them and a suction is created

Water vascular system- defining characteristic

Sun star

  • Up to 40 arms

Sun Star

Class stelleroidea

  • Sea Stars

  • Subclasses: Asteriudea and Ophiuroidea

  • Asteriudea are true sea stars

Class Stelleroidea






Sea star anatomy

  • Spiny skin

  • No backbone

  • Endoskeleton made of ossicles. Ossicles form a web under skin

  • Covered in calcium plates

  • Oral surface is ventral. Anus is aboral

  • Typically 5 arms

  • 2 rows of tube feet with ampulla (bulb like muscles for tube feet)

  • 2 stomachs- Cardiac and pyloric stomachs. Eat with stomach inside out. carnivores

  • No intestine

  • Open circulatory system

  • No respiratory or excretory organs

  • Sexual and asexual reproduction

Sea star anatomy

Sea star anatomy1

  • No head, brain or blood. Has a nerve ring around mouth and radial nerves running inside each arm

  • Eyespot on the tip of each arm to sense light and dark

  • Madreporite- opening to water vascular system. water enters through sieve like plate on aboralsurface

  • Tube feet

  • Ambulcaral groove

  • Central disk

Sea star anatomy

Tube feet

  • Ambulcaral groove- groove containing rows of tube feet used to attach to surfaces


Tube feet

Feeding digestive system

  • Eat clams, mussles, barnacles, coral, sea urchins

  • Tube feet grip prey

  • Coelomate body cavity- nutrients absorbed into and moved through cavity

  • Two stomachs

    • Cardiac stomach- can be turned inside out through the mouth through a process called eversion

    • Pyloric stomach- connected to digestive glands in each arm. Where absorption occurs

Feeding/digestive system



  • Watch the cardiac stomach protrude



  • Separate sexes

  • External fertilization

  • Eggs and sperm shed into water

  • Larvae are bilaterally symmetrical

  • Metamorphosis into pentaradialsymmetry for adults



Some Sea stars can change their gender when it is convenient to them.

  • AsterinaGibossa are born male but later they change themselves into females. Also there are some other species of starfish that can change their gender with the change of temperature and it also depends on the availability of food


  • The female starfish is capable is releasing over 2 million eggs at any one time, although the average amount of eggs that the female starfish releases is closer to 1 million. The eggs released by the female starfish are then fertilized by the male starfish and the fertilized eggs develop into larvae which are able to swim about. Starfish larvae swim for about three weeks before settling and beginning metamorphosis into the more common appearance of the starfish


  • Regeneration- arms regenerate IF a portion of central disc is attached. Very slow process

  • Sea stars and sea cucumbers

  • Makes them very hardy

  • Form of asexual reproduction





Sea star anatomy videos



Sea star anatomy videos

Class ophiuroidea

  • Brittle stars. Also known as serpent sea stars

  • Thinner arms

  • Distinct body

  • Do NOT use tube feet for walking

  • Instead, tube feet create mucous strand which catch food and move it toward mouth

  • Will also grab food and bring it to mouth with curled arm

Class Ophiuroidea

Brittle star photo

Brittle star photo

Difference between sea star and brittle star

  • Sea stars have thicker arm. Brittle stars have very thin arms

  • Brittle stars do not use tube feet for movement

Difference between sea star and brittle star

Brittle star video


  • Brittle star eating clam

Brittle star video

Keystone species


  • What is a keystone species?

Keystone Species

Class echinoidea

  • Sea urchins and sand dollars

  • Herbivores- eat algae

Class Echinoidea

Sea urchin

  • Sea urchins- 700 species

  • Spines are all under individual muscle control

  • Anus and genital pores on top of sea urchin

  • Sea urchins have five paired rows of tiny tube feet which are found amongst the spines. The feet of the sea urchin have suckers which help the sea urchin to move about, capture food, and to hold onto the ocean floor

Sea urchin

2 lines of defense

  • 1.spines- The length and sharpness of an urchin’s spines vary from species to species. Some species have stubby, blunt spines, while other species have long, sharp, venom-filled spines. Razor sharp spines can easily pierce even a thick wetsuit and lodge deep in a diver’s skin.

  • 2.Many urchin species, such as the purple sea urchin, have an additional defense mechanism called the pedicellarines. The pedicellarines are tiny, jaw-like structures that can clasp onto a diver’s skin and inject a painful poison. The pedicellarines are nestled down between the urchin’s spines, and are difficult for a diver to contact unless he has already impaled himself on the urchin’s spines.

  • In extreme cases, such as numerous puncture wounds, the relatively small amount of venom from spines and pedicellarines can accumulate to cause severe muscle spasms, faintness, difficulty breathing, and death.

2 lines of defense


  • flower urchin, have venom-tipped spines that can cause severe pain to careless divers.

Aristotle s lantern

  • The mouth of most sea urchins is made up of five calcium carbonate teeth or jaws, with a fleshy, tongue-like structure within. The entire chewing organ was known as Aristotle's lantern

  • Aristotle’s Lantern- 5 tooth like plates that point inward

Aristotle’s Lantern

Aristotle s lantern1

Aristotle’s lantern

Sea urchin anatomy

Sea urchin anatomy


  • The red sea urchin is the longest living creature on earth, with some living more than 200 years

Sea urchin1


Sea urchin

Sand dollar

  • Sand dollars and heart urchins- “flattened urchins”

  • Suspension feeders

  • Spines used for movement. NOT tube feet

  • 5 pores on body are for gas exchange

Sand Dollar

Sand dollar anatomy

Sand dollar anatomy

5 doves

The legend of the Sand Dollar...Upon this odd-shaped seashell a legend grand is told,about the life of Jesus, that wondrous tale of old.At its center you will see, there seems to be a star,like the one that led the shepherds and wise men from afar.Around its surface are the marks of nails and thorns and spear,suffered by Christ upon the cross; the wounds show plainly here.But there is also an Easter lily, clear for us to see,the symbol of Christ's resurrection for all eternity.Break the center open, and you will releasethe five white doves awaiting to spread good will and peace

“5 Doves”

What are the five doves of the sand dollar

What are the “five Doves” of the Sand Dollar


  • The individual pieces of the jaw (aka the Aristotle's Lantern -which are often broken) is probably what you hear rattling around inside when you pick one up off the beach...

  • OR

  • The "doves of peace" are the broken fragments of the Aristotle's Lantern, i.e, the jaw the animal used to crush and grind sand. The "Star of Bethlehem" is a neatly dissected, complete jaw from the inside of the sand dollar

Sand dollar video


Sand dollar video

Class holothuroidea

  • Sea cucumbers

  • Mouth at one end, anus at opposite

  • Tube feet down one side of organism in 5 areas

  • When threatened, some sea cucumbers discharge sticky threads to ensnare their enemies.

  • Ability to eviscerate (expel) their internal organs when attacked. Regenerates expelled organs

  • Tentacles filter seawater- filter feeders

  • No ossicles

  • Soft body

  • Madreporite is internal

Class Holothuroidea

Sea cucumber photo

Sea cucumber photo

Sea cucumber video 2 21


Sea cucumber video 2:21

Class c rinoidea

  • Sea lillies and feather stars

  • “upside down brittle stars” with ambulacral grooves and mouth directed upward

  • Suspension feeders

  • Use tube feet to secrete mucous which traps food

  • Food is passed down food groove in center of arms

  • No spines, no madreporite, no pedicellariea

Class Crinoidea

From encycolpedia britannica

  • a lily, any crinoid marine invertebrate animal (class Crinoidea, phylum Echinodermata) in which the adult is fixed to the sea bottom by a stalk. Other crinoids (such as feather stars) resemble sea lilies; however, they lack a stalk and can move from place to place. The sea lily stalk is surmounted by a bulbous body with frondlike tentacles, and the animal resembles a plant. The stem consists of limy disks, and the body has an internal skeleton of close-fitting limy plates.

From encycolpediabritannica

Sea lilly photo

Sea lilly photo

Sea feather

Sea feather


  • Sea star

  • Sea cucumber

  • Sea urchin

  • Sand dollar


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