Echinoderms The spiny misfits
General Characteristics Larvae have bilateral and adults have radial symmetry No head! Endoskeleton- calcium carbonate
Water vascular system Pattern of development in embryos is more similar to vertebrates
General Characteristics Number of arms is in multiples of 5 Separate sexes Nerve ring Open circulatory system Body cavity
Body Most are carnivorous with a complete digestive tract Nervous system is simple looking but these orgs have complex behavior Regeneration is highly developed
Network of water filled canals Connects to the outside by a pore called the madreporite Water Vascular System
Tube feet extend when filled with water thru canals Used for locomotion and attachment
CLASSES OF ECHINOS Asteroidea Ophiuroidea Echinoidea Holothuroidea Crinoidea
Asteroidea- sea stars Slow moving, flexible arms Predators of bivalves, snails, barnacles (slow- moving or attached animals) Feed by everting stomach thru mouth
Ophiuroidea- brittle stars Arms very flexible and can move quickly Deposit feeders Largest group of echinos but stay hidden
Echinoidea- sea urchins, sand dollars Round hard endoskeleton with movable spines Graze on sea weed and sea grasses as well as scavenge Aristotle’s lantern- special mouth and jaw parts
Holothuroidea- sea cucumbers Worm like Deposit feeders Interesting defense mechanisms –Secrete toxins –Discharge mucus and toxins thru their anus –Eviscerate guts thru mouth or anus (they’ll grow back)
Crinoidea- feather stars and sea lilies Suspension feeders with feathery arms for feeding Deep water and either attached to the bottom or crawl