Download Invertebrates - Echinoderms

Invertebrates
Phylum: Echinodermata
• All marine
• Known as spiny-skinned animals
• Includes sea stars, brittle stars, sand
dollars, sea urchins, & sea cucumbers
Includes 5 classes:
1. Crinoidea - sea lilies & feather stars
2. Asteroidea - starfish
3. Ophiuroidea - basket stars & brittle
stars
4. Echinoidea - sea urchins & sand
dollars
5. Holothuroidea - sea cucumbers
Feeding & Digestion
• Tube feet attach to bivalve mollusk shells &
create suction to pull valves apart slightly
• Starfish everts (turns inside out) its stomach
through its mouth & inserts it into prey
(bivalve)
• Stomach secretes enzymes to partially digest
bivalve then stomach withdrawn & digestion
completed inside starfish
• http://www.ehow.com/video_4908973_starfisheat_.html
WATER VASCULAR SYSTEM
• Water enters through madreportite
(sieve plate) on aboral (oposite side of
mouth) surface into a short, straight
canal
• canal connects to a circular canal
around the mouth called the ring canal
• Five radial canals extend down each
arm & are connected to the ring canal
• Radial canals carry water to hundreds
of paired tube feet
Network of canals creating hydrostatic pressure to
help the starfish move
TUBE FEET
• Bulb-like sacs or ampulla on the upper
end of each tube foot contract & create
suction to help move, attach, or open
bivalves
• Rows of tube feet on oral surface
(underside) are found in ambulcaral
grooves under each arm
Other Body Systems
• No circulatory, excretory, or respiratory
systems
• Coelomic fluid bathes organs & distributes
food & oxygen
• Gas exchange occurs through skin gills &
diffusion into the tube feet
• No head or brain
• Have a nerve ring surrounding the mouth
that branch into nerve cords down each arm
• Eyespots on the tips of each arm detect light
• Tube feet respond to touch
Reproduction
• Separate sexes
• Two gonads (ovaries or testes) in each arm
produce eggs or sperm
• Have external fertilization
• Females produce up to 200,000,000 eggs per
season
• Fertilized eggs hatch into bipinnaria larva
which settles to the bottom after 2 years &
changes into adult
• Some can reproduce asexually reproduce by
splitting in two halves which then grow into
complete individuals.
Echinoidea
• Sand Dollar
• Sea Urchin
• Sea Lilly
• Feather star
• (Asteroidea)Starfish
• Basket star
(Ophiuroidea)
• Brittle star (Ophiuroidea)