Zoology lecture 12

What symmetry do echinoderms have

Radial as adults, bilateral as larvae

What kind of skeleton do echinoderms have

Endoskeleton of calcium carbonate ossicles

What type of coelom and cleavage do they have

Coelomate with radial cleavage.

Do echinoderms have a brain or excretory system?

No brain, no excretory organs

What does the water vascular system do?

Moves tube feet for locomotion, feeding, and respiration

Trace the path of water through the WVS.

Madreporite → stone canal → ring canal → radial canal → ampullae → tube feet.

How do sea stars feed?

Evert stomach into prey (usually bivalves).

What structure do sea urchins use to feed?

Aristotle’s lantern

How do echinoderms reproduce?

Mostly dioecious, external fertilization, bilateral larvae.

Can echinoderms regenerate?

Yes — many can regrow arms or entire bodies.

What are the 3 main classes of echinoderm

Asteroidea, Echinoidea, Holothuroidea,

Key traits of Asteroidea?

Sea stars; arms with suckered tube feet; evert stomach; regeneration.

Key traits of Echinoidea

Urchins & sand dollars; spines & tube feet; Aristotle’s lantern; no arms

Key traits of Holothuroidea?

Sea cucumbers; soft body; tentacle-like tube feet; can eviscerate; filter feeders.

What are unique features of echinoderms?

Radial symmetry, endoskeleton, water vascular system, tube feet, regeneration, no brain.

What side is the mouth on in sea stars?

Oral surface (underside).

What’s the opposite side called?

Aboral surface (upper side).

Water enters through a

valve called the

madreporite

madreporite

Water vascular system

s a system of water-filled

canals that function as a hydrostatic skeleton &

connects each tube foot to the other

enterocoelous coelom formation

coelom, develops from pouches that bud off from the archenteron (the primitive gut)