Download Phylum Echinodermata

Phylum Echinodermata
Lauren and Simon
Echinoderms– echin (spiny) and derma (skin)
GENERAL INFORMATION
Symmetry
Secondary Radial Symmetry– the larvae
are bilateral and the adults are radial
Water Vascular System
• Distinctive aspect to echinoderms
This is what echinoderms use in order to move,
do respiration, and transport food and waste. It
a system that consists of canals connected to
tube feet (tubular projections like in the arms
of a starfish) and it uses hydraulic pressure in
order to operate
• At the base of the foot there is a sac called the
ampulla that holds fluid. When it contracts,
water shoots down the foot and extends it.
The white
http://www.youtube.com/watch?v=4IRF-pKVtuU&feature=related
parts are where
the tube feet
are in this sea
urchin
http://webs.lander.edu/rsfox/invertebrates/introduction.html
Body Development
• The Echinodermata has a two stage
development—the larvae and the
adult. When the larvae grows, its left
side then grows a lot, and the right
side gets absorbed. The left side then
grows in a 5 part radial symmetrical
fashion, creating the adult
echinodermata.
Germ Layers
• Triploblastic
Reproduction
•Gametes put into water in bursal sacs
•Becomes a larva after fertilization and undergoes
metamorphasis without attachment
Examples
Basket Star
Brittle Star
Unique Abilities
Echinoderms have a special kind of tissue
connected to ossicles (plates made of
calcium carbonate) that can change their
consistency from solid to liquid very
quickly. This phenomenon allows
echinoderms to do amazing things:
• Sea urchins can move or lock their spines
• Brittle and sea stars can bend or purposely
break off an arm
• Sea cucumbers can move/flow into narrow
places and harden when it is in a safe place
http://www.wildsingapore.com/chekjawa/text/p600.htm
CLASSES
Asteroidea (Sea Stars)
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Mostly eat clams and oysters or other animal that is too slow to defend itself
It slowly pries open its prey in order to eat it, sending out its stomach to
consume the body of the shellfish
They have two stomachs—one is used to eat and the other is used for digestion
Like all echinoderms, it has a complex nervous system, but no brain
They have eyespots that are light sensitive
They have other sensory perception such as touch
Unlike the brittle star, sea stars’ organs enter their arms.
They can break off their arms and the arms can regenerate
Holothuroidea (Sea Cucumber)
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Sea cucumbers are scavengers, looking for food at the
bottom of the ocean
They usually live in tropical reefs
If it is threatened, it will stiffen and a jet of water will
shoot out of one end
If they feel threatened, they can also throw out their
internal organs to distract predators, then grow new organs
Sea cucumbers can form dense populations
They can grow up to 16 inches
They use their tube feet to move very slowly
Echinoidea (Sea Urchin and Sand Dollars)
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The pores in a sand dollar allow water to enter its Water vascular
system, allowing it to move
Sand dollars usually live together at the bottom of the ocean
Sand dollars become bleached and loose their spines when left out in
the sun on the beach, so the ones in the store are very different from
live ones
Sea urchins have teeth made of calcium carbonate, and the entire
chewing organ is called Aristotle's Lantern
Sea urchins mainly eat algae, but can also eat other invertebrates like
mussels, sponges, and brittle stars
Sea urchins’ spines protect it from predators, but it is not clear whether
the spines or the pedicelleriae (appendages used to keep encrusting
organisms off) between the spines are venomous
Crinoidea
•Rays collect food
•Pinnules increase surface area
•Calyx contains most of the organs
•Filter feeders – tube feet move particles down the
ambulacral groove
•Saccule excretes
Inner structure of a ray
in the calyx
Feather Star
Sea Lily
• Sea lilies were once thought to be planted in the ground but
researchers found out that they actually can crawl from danger
at 5 cm/s. They use their leg-like “petals” to crawl along the
ocean floor. They use a lizard-like technique and leave their
roots behind when escaping predators.
http://www.umich.edu/news/index.html?Releases/2005/Oct05/crinoid
Ophiuroidea
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Pentaradial symmetry
Calcium Carbonate skeleton
Water vascular system that ends with tube feet
Long and nearly solid rays which move like snakes
Arms can regenerate
Carnivores, filter feeders, and scavengers
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Five jaws
10 bursae are used for
excretion
Coelem is smaller than other
echinoderms
No eyes
Epidermis is sensitive to light
and other stimuli
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