Phylum Echinodermata III

Question 1

Echinoidea Characteristics (3)

Answer 1

No arms
Endoskeleton: large flat ossicles (test), spines & pedicellariae
Aristotle’s lantern: device to move teeth

Question 2

Aristotle’s lantern

Answer 2

Teeth protruding from the mouth (5 teeth) controlled by a complex of internal ossicles (50) and muscles (60)

Question 3

Regular echinoids

Answer 3

Rocky substrates
Locomotion: spines and tube feet (suckers)
Feeding: scrape algae from rocks, shred kelp, capture drift algae with tube feet

Question 4

Irregular Echinoids

Answer 4

Superimposed bilateral symmetry due to movement of anus and mouth
Sand/mud substrates
Locomotion: spines only
Feeding: deposit feeding (tube feet)

Question 5

Petaloid Tube Feet

Answer 5

Specialized tube feet for gas exchange in sand dollars on the aboral surface
The beating of cilia encourages diffusion into the internal

Question 6

Ophiuroidea (brittle star) body form

Answer 6

5 well-articulating arms radiate from a central disk
Highly articulate arms due to vertebral ossicles connected by ball and socket joints
Perivisceral coelom greatly reduced

Question 7

Basket Stars

Answer 7

Ophiuroids with branched arms for suspension feeding

Distal ends of branched flexible arms that coil around prey (zooplankton)

Question 8

Ophiuroidea Distinctive Characteristics (6)

Answer 8

Central disc with highly flexible arms 
Locomotion by arm rowing 
Arm autonomy (MCTs)
No anus 
Tube feet lack suckers & ampullae 
Bursae for gas exchange

Question 9

Crinoidea (5)

Answer 9

Primitive echinoderm characteristics 
Stalk or cirri for substate attachment 
Mouth facing upwards 
Arms with pinnules 
Can lock MCTs of ossicles so they do not expend energy when stationary

Question 10

Crinoidea Primitive character state (5)

Answer 10

Central disc with radiating arms 
Ossicles as articulating discs 
Tube feet for suspension feeding 
Mouth oriented upward 
MCTs for long term maintenance of posture with no energy expenditure