Echinoderms

Sam & Jen

Examples of Subgroups• Crinoidea

– Sea Lillies• Asteroidea

– Sea Stars• Ophiuroidea

– Brittle stars• Echinodea

– Sea Urchins & Sand Dollars • Holothuoidea

– Sea Cucumbers• Blastoidea

– Blastoids

Star Fish

Sea Lilly

Sea Urchin

Body Systems• Circulatory

– none• Excretory

– Diffusion through tube feet, anus, or skin gills(no kidneys)• Nervous

– Nerve ring(circles mouth) & radial nerve(from nerve ring down each are)

• Reproductive– External Fertilization

• Sperm and eggs released into water

– Asexual (regeneration)• Can lose a ray to escape from predators and regrow it

Tube Feet

Characteristics

• Multicellular w/o cell walls

• Heterotroph– Mouths located on oral(underside) of body

• Pentaradial Symmetry– 5 rays(arms) branching from central body

• Deuterostome– Anus develops then mouth

More characteristics

• Pedicellariae– Tiny, jaw-like pinchers on skin

• Protection & self cleaning

• Dermal Endoskeleton– Hard, spiny or bumpy– Made of calcium carbonate plates

• Called ossicles

Water Vascular System

• Hydraulic system that operates under water pressure– Allows for movement, gas exchange, capture

of food, excretion– Parts: Tube feet & Ampullae– Water enters through madreporite

• Acts as filter

Water Vascular System

Body Cavity

• True Coelom(body cavity)– Fluid inside bathes organs– Distributes nutrients & oxygen

Sea CucumberBrittle Stars