Phylum Echinodermata

Some Representatives of Echinodermata copyright cmassengale

Copyright Pearson Prentice Hall Echinoderms characteristic summary:  spiny skin (Echinoderm means “spiny skin”)  an internal skeleton  a water-vascular system  suction-cup structures called tube feet

Evolution & Classification  Echinoderms are from the Cambrian period & date back to over 500 million years ago  Scientists believe that they evolved from bilaterally symmetrical ancestor.  Modern echinoderm larva is similar to proposed ancestral species.  Echinoderms are deuterostomes, animals in which the blastopore develops into an anus  This fact leads them to be most closely related to the phylum Chordata (also deuterostomes)

 A sudden rise or fall in the number of echinoderms can cause major changes to populations of other marine organisms.  Sea urchins help control the distribution of algae and other forms of marine life.  Sea stars are important predators that help control the numbers of other organisms.  The crown-of-thorns sea star has destroyed extensive areas of coral in the Great Barrier Reef of Australia. Ecology of Echinoderms

Echinoderm Body Plan :  Coelomates  No cephalization (no head or brain)  Most have five radii which is known as pentaradial symmetry  Two rows of tube feet run along the underside of each arm.  Endoskeleton that is made up of calcium plates called ossicles, and they may include protruding spines

Echinoderm Body Plan :  The side of the body where the mouth is located is referred to as the oral surface.  The opposite side is called the aboral surface.  The body of a sea star is usually covered with short spines.  Surrounding each spine in many sea stars are numerous tiny pincers called pedicellariae.

Biology/START%20Power%20Presentations.html

 Do not have circulatory, respiratory, or excretory systems  Echinoderms have a system of internal tubes called a water vascular system.  The water vascular system carries out many essential body functions, including respiration, circulation, and movement. Form and Function in Echinoderms

The most distinctive system of echinoderms is the water-vascular system, shown here in a sea star. The Water Vascular System

The water vascular system opens to the outside through a sievelike structure called a madreporite. madreporite The Water Vascular System

A tube foot is attached to each radial canal. The upper end of each tube foot is called an ampulla. These contract forcing water into the tube foot making it extend. The Water Vascular System

Tube feet act together to create enormous force allowing echinoderms to “walk,” and pull open shelled prey. The Water Vascular System Video

Echinoderms have several methods of feeding.  Sea urchins scrape algae from rocks.  Sea lilies use tube feet to capture floating plankton.  Sea cucumbers move across the ocean floor, taking in sand and detritus using mouth tentacles. Feeding & Digestion

 Most sea stars are carnivorous and they tend to each mollusks  The sea star can turn its cardiac stomach inside out through its mouth when it feeds.  The cardiac stomach transfers food to the pyloric stomach, which connects to a pair of digestive glands in each arm. Feeding & Digestion

 Thin-walled tissue of the tube feet provides the main surface for respiration.  In some species, small outgrowths called skin gills also function in gas exchange.  Circulation of materials and wastes takes place using the water vascular system. Respiration & Circulation

 Digestive wastes are released as feces through the anus.  Nitrogen-containing cellular wastes are excreted primarily in the form of ammonia.  This waste is passed into surrounding water through tube feet and skin gills. Excretion

 Have a nerve ring that surrounds the mouth, and radial nerves that connect the ring with the body sections.  Have scattered sensory cells that detect light, gravity, and chemicals released by potential prey. Response

 A nerve ring surrounds the mouth with a radial nerve in each arm  Eye spots respond to light  Tentacles respond to touch

 Most echinoderms move using tube feet.  Sand dollars and sea urchins have movable spines attached to the endoskeleton.  Sea stars and brittle stars use their arms for locomotion.  Sea cucumbers crawl by using both tube feet and the muscles of their body wall. Movement

 Most echinoderms have separate sexes.  Each arm of the sea star contains a pair of ovaries or testes.  Fertilization occurs externally in water.  Each fertilized egg develops into a bilaterally symmetrical, free-swimming larva called a bipinnaria.  Echinoderms also have remarkable powers of regeneration (asexual) Reproduction & Development

Class Crinoidea (means “lily-like”)  Members of the class Crinoidea, called crinoids, include the sea lilies and feather stars.  In both types of crinoids, five arms extend from the body and branch to form many more arms—up to 200 in some feather star species. The 5 Echinoderm Classes

 Crinoidea are sessile  They have long stalks that attach to rocks or to the ocean floor  Sticky tube feet that are at the end of each arm catch food and serve as a respiratory surface. Crinoidea (“lily-like”)

Class Ophiuroidea (means “snake-tail”)  Ophiuroidea is the largest Echinoderm class  Basket stars and brittle stars  Members of this class are distinguished by their long, narrow arms, which allow them to move more quickly than other echinoderms.

Ophiuroidea (“snake-tail”)  Primarily live under stones & in crevices and holes of coral reefs  Have thin brittle arms that break off & regenerate quickly  Feed by raking food off the ocean floor with their arms and bottom of tube feet

Class Echinoidea (means “spinelike”)  Echinoidea consists of about 900 species of sea urchins and sand dollars  The internal organs are enclosed within a fused, rigid endoskeleton called a test

Echinoidea (“spinelike”) Sea Urchins  Live on rocks or coral reefs  A complex jaw-like mechanism called an Aristotle’s lantern is used to grind their food  Scrape food/algae off rocks and coral

Sand Dollars  Live along seacoasts & sandy areas  Flat, round shaped bodies adapted for shallow burrowing – use short spines to move and dig  Filter feeders

Class Holothuroidea (means “water polyp”)  Sea cucumbers belong to the class Holothuroidea.  Armless soft bodies  Live on the sea bottom, where they crawl or burrow into soft sediment by using their tube feet.

Holothuroidea (“water-polyps”)  Feed with tentacles around the mouth which sweep up sediment from the water  Can protect themselves by ejecting internal organs – called evisceration

Class Asteroidea (means “star-like”)  Sea stars, or starfish, belong to the class Asteroidea, which means “starlike”  found all over coastal shores around the world  Eat mollusks k12.wi.us/staff/hutch croft/Biology%20Not es/Power%20Present ations- Biology/START%20P ower%20Presentatio ns.html