Download Phylum Echinodermata Slide Show

Kingdom Animalia
Phylum Echinodermata
General Characteristics
• Name means “spiny skin”
• Possess an endoskeleton or internal skeleton
• Water vascular system and suction-cup-like
structures called tube feet
• most adult forms exhibit pentaradial symmetry
• Only live in marine environments
• Regeneration – can re-grow some body parts when lost
Classification & Examples:
Class Echinoidea
Sea Urchins & Sand Dollars
• Large, solid plates form a box around the
internal organs
• Detriovores or grazers which eat algae
(seaweed)
Classification & Examples:
Class Ophiuroidea - Brittle Stars
• Common on coral reefs
• Filter feeders and
detritovores
• Hide during the day and
feed by night
• Will shed one or two rays
to avoid being eaten
totally.
Classification & Examples:
Class Holothuroidea Sea Cumbers
• Detritus feeders – suck
up organic matter and
remains of other
organisms while crawling
along the sea floor
• Will regurgitate their
internal organs in order
to avoid predators – then
re-grows organs at a later
time.
Classification & Examples:
Class Asteroidea - Sea Stars
• Creep along the ocean
floor
• Most are carnivorous,
eating bivalves.
• If a sea star is pulled into
pieces, each piece will
grow into a new
individual as long as it
contains a portion of the
central disc.
Echinoderm Video
Feeding
• Method varies from species to
species
• Sea urchins use a five-part
jaw-like structure to scrape
algae from rocks. (click
picture for animation)
• Sea cucumbers ingest sea floor
sediments, digesting out the
organic material.
• Sea stars feed on bivalves by
pushing their stomachs out of
their mouths into the shell of
the prey, exuding enzymes,
and then digesting the
resulting “soup”.
Respiration & Circulation
• The water vascular system is
responsible for most
respiration and circulation.
• Respiration (in most species)
occurs through the thin walls
of the tube feet. Few species
have small outgrowths called
“skin gills”.
• Nutrients and gases are
circulated through the water
vascular system.
Excretion
• Digestive wastes (feces) are released
through the anus.
• Cellular wastes are passed through the
thin walls of the tube feet and skin gills in
the form of ammonia.
Response
• The nervous system is not
highly developed in
Echinoderms.
• A nerve ring surrounds the
mouth.
• Radial nerves connect the
nerve ring with the body
sections.
• A variety of scattered sensory
cells detect light, gravity, and
chemicals released by prey.
Movement
• Most move using tube feet (part of the
water vascular system)
• The shape and size of the plates of the
endoskeleton help determine the range of
mobility. Smaller plates mean increased
flexibility and mobility.
Reproduction
• some echinoderms (e.g., sea stars, brittle stars) able to
reproduce asexually by separating central disk into 2 pieces
• •sea cucumbers also able to reproduce asexually by breaking
in half (transversely) - each half regenerates missing parts
• •however, most echinoderms only reproduce sexually
• -usually fertilization is external (i.e., gametes are released into
surrounding seawater)
• bilaterally-symmetrical, ciliated larvae result from union of
gametes
Sea Star Animation
• Click here