Phyla

Echinodermata Sarah Doyle & Lauren Dombkoski

Echinoderms

• a slow-moving or sessile marine

deuterostome with a water vascular system

and, in adults, radial anatomy

• 6000 species, all marine

Living Echinoderms are divided

into six classes...

• 1- Asteroidea: sea stars aka starfish

• - star shaped body with multiple arms; mouth

directed to substrate

Classes, continued

• 2- Ophiuroidea: brittle stars

• - Distinct central disk; long, flexible arms;

tube feet lack suckers

Classes, continued

•3 - Echinoidea: sea urchins and sand dollars

• - Roughly spherical or disk-shaped; no arms;

five rows of tube feet enable slow movement;

mouth ringed by complex, jaw-like structure

Classes, continued

• 4 - Crinoidea: sea lilies and feather stars

• - Feathered arms surrounding upward-pointing

mouth

Classes, continued

•5 - Holothuroidea: sea cucumbers

• - Cucumber-shaped body; five rows of tube feet;

additional tube feet modified

Classes, continued

•6 - Concentricycloidea : sea daises

• - Disk-shaped body ringed with small spines;

incomplete digestive system; live on submerged

wood

Physical Description

• adult forms have radial symmetry

• larvae are bilateral

• varied skeletal and muscular arrangement

• water vascular system

• Respiration

• gills on the skin

Reproduction

• there are 2 sexes

except:

o asteroids&echinoids -

multiple gonads in arms

o crinoids - lack distinct

gonads

o holothurians - single

gonad

• gametes are released

into water

Characteristics

•Behavior

• most are immobile

• water vascular system originally for food

collection but now evolved for locomotion

• Communication

• non-central nervous system: movement is

sense from all sides

• Development

• deuterostomes: anus forms first, then mouth

Food

• Crinoidea

• sit with arms out and collect passing food

• Asteroidea

• predators or scavengers; everts stomach

and secretes digestive enzymes on prey;

suspenson feeders, too

• Ophuroidea

• imcomplete digestive system; predators,

deposit feeders, and scavengers

Food, cont.

• Echinoidea

• suspension feeders,

herbivores, detritivores,

predators

• Holothuroidea

• suspension or deposit

feeders; use digestive

organs in response to threat

• group of hard plates that

retract and grasp like teeth

Execretion

• amoeboid cells carry wastes out of the body

Predation

• most vulnerable in larval stage

• asteriods: o anti-predator adaptation

• holothurians o discharge, sticky tubules called Cuvierian tubules

Starfish

Class: Asteroidea

Cirulatory System:

- Water-vascular system and tube feet

- hemal system

Nervous System:

- nerve plexus

- ringed nerves

Starfish

• Digestion and Excretion:

• - mouth is located on underside of the body

• - Has a digestive tract

• Reproduction:

• - each arm contains two gonads and releases

gametes into surrounding water

• - fragmentation

• Symmetry:

• - pentamerous symmetry

Feather Stars

• Class: Crinoidea

•Circulatory System:

• - Water-vascular system and tube feet

• - do not use tube feet for locomotion

• Nervous System:

•- Has small sensory cells throughout their skin

•- Central nervous ring around the mouth,

arms, and base

Feather Stars

• Digestion and Excretion:

• - Captures particles or plankton

• - Has a digestive tract

• Reproduction:

• - releases sperm and egg into surrounding

water

• Symmetry:

• - radial symmetry

Sea Urchin

• Class: Echinoidea

• Circulatory System:

• - Water-vascular system and tube feet

• Nervous System:

• - no true brain

• - Central nervous ring around the mouth

Sea Urchin

• Digestion and Excretion:

•- Has a mouth containing teeth, jaw, and

tongue like structure

• - Has a digestive tract

• Reproduction:

• - releases sperm and egg into surrounding

water

• Symmetry:

• - radial symmetry