Echinoderm Overview

Question 1

Describe the larvae of Echinoderms

Answer 1

Mouth, Anus- Simple structure
Have bilateral symmetry
Ciliary bands for movement
Sensory tuft- measure G force of current

Question 2

Give the 5 different echinoderm forms

Answer 2

Asteroidea- Starfish, Seastar
Ophiuroidea- Brittle star
Crinoidea- Sea lily, feather star
Echinoidea- Sea Urchin
Holothuroidea- Sea cucumber

Question 3

Give the symmetry of echinoderms

Answer 3

Pentaradial symmetry

Question 4

What species do asteroidea include

Answer 4

Starfish and Seastars

Question 5

What do asteroidea feed on ?

What are the problems associated with this ?

Answer 5

Coral

Coral is slow growing, asteroidea are rapid grazers which can lead to an ecosystem imbalance.

Question 6

Describe the mouth of an asteroidea.

Answer 6

Composed of simple skeletal plates

Question 7

Give one species of asteroidea that has more than 5 limbs.

Answer 7

Crown of thorns starfish

Question 8

What is found on the ORAL surface ?

Answer 8

Tube feet, Mouth, ambulacral grooves

Question 9

What is found on the ABORAL surface ?

Answer 9

Anus, Madreporite (regulation of water pressure)

Question 10

Which species has the same body plan as the asteroidea ?

Answer 10

Ophiuroidea

Question 11

Describe the body plan of the Crinoidea.

Answer 11

Have a stalk like structure that attaches to the substrate.

The aboral surface becomes the lower surface. The oral surface the upper surface (for prey capture, top of stalk)

Question 12

Describe the body plan of the Echinoidea.

Answer 12

Sea urchins, ball shape

Whole animal is covered in the Oral surface. (developed spines)

Question 13

Describe the body plan of the Holothuroidea

Answer 13

Sea cucumber, cylindrical

Whole animal covered in Oral surface. (means of movement)

Question 14

How do sea cucumbers protect themselves from predation ?

Answer 14

Culverian tubules produce slime when hassled by prey.

Vomit their guts. The sticky filaments can damage and entangle their predator.

Question 15

Which group of species has the smaller arms, Asteroidea or the Ophiuroidea ?

Answer 15

The Asteroidea

Question 16

Where are the tube feet found ?

Answer 16

On the Oral surface, in the AMBULACRAL GROOVES.

Question 17

Describe the body plan of the Asteroidea.

Answer 17

Oral surface is the lower surface, Aboral surface is the upper surface

Question 18

Describe how the tube feet contribute to movement.

Answer 18

Pressure System.
Madreporite pumps water into the organism,
Water enters radial canal.
This water is pumped into the ampulla
The muscles fibres of ampulla contract
Water is stopped from leaving the radial canal.
Water moves to tube feet, extending them

Question 19

Give the advantages of tube feet.

Answer 19

Individual tube feet can be extended and retracted separately
The girth of the feet can be modified giving suction on smooth surfaces.

Question 20

How is rigidity achieved in the asteroidea ?

Answer 20

Calcified Ossicles (small bones) 
Spines protect gaps between these bones.

Question 21

What is found in the legs of most echinoderms ?

Answer 21

Pyloric cecum- produces enzymes and stores food
Gonads- produce gametes
Radial canal- receives and passes on water
Tube foot- movement
Ampulla-contracts to let water enter the tube foot.

Question 22

Which group contains no parasitic species ?

I.e do not use other species

Answer 22

Ophiuroidea

Question 23

Give a key adaption of the Ophiuroidea that prevents parasites.

Answer 23

Spines, prevent parasites from attaching to body.

High risk as slow moving

Question 24

Describe the endoskeleton of the Holothurian.

Answer 24

Comprised of 100 um calcium carbonate plates which fit together.

Question 25

Describe the endoskeleton of the Echinoid.

Answer 25

Complicated Test (shell)
3-10 cm across
Round (effective against big predators)
Spiny,

Question 26

Echinoids have a variety of plates, list them and give their functions.

Answer 26

Gential- External fertilisation occurs by spawning.
Mouth- Acts as teeth, Usually herbivores
Ocular- covered in Photo receptors (dark n light). Regulation of depth.

Question 27

Describe the function of echinoid spines.

Answer 27

Mobile spines- Movement

Defence spines-inject toxins and poisons to create infection in predators

Question 28

What is the morphology of the echinoid spines ?

Answer 28

Muscles link the spine to the test/shell.
A sheath of muscle, containing poisonous glands surrounds the spine.
Sheath will be retracted to expose spine.

Question 29

In what classes is the Pedicelaria found ?

Answer 29

Echinoderms and Asteroidea

Question 30

What is the Pedicelaria ?

Answer 30

A modified spine that keeps the surface of the echinoderm free from settling organisms
2 Types- Cutting Jaws, Simple Nipping

Question 31

Which species uses their Pedicelaria to kill prey ?

Answer 31

Stylasterias (fish eating starfish)

Question 32

Which echinoderm appendage was originally thought to be a separate organism ?

Answer 32

Pedicelaria

Question 33

Describe the process of a echinoid feeding on a bivalve

Answer 33

Capture bivalve with tentacles
Use tube foot to open shell
Insert stomach into shell
Release enzymes to break down the closing muscles of the bivalve
Reabsorb stomach 
Evert waste through the mouth,

Question 34

Give the key feature of echinoid teeth.

Answer 34

Continually growing, preventing them from ever becoming blunt.

Question 35

Give the site of respiration In the holothurian.

Answer 35

Respiratory tree, site of O2 exchange

Question 36

Give the one species of echinoderm which can regenerate fully.

Answer 36

Linkia comets, can regenerate from one arm

Question 37

The more basal the organism….

Answer 37

… The more able the organism is to regenerate.

Question 38

What is mutable connective tissue ?

Answer 38

If moved slowly, will be a solid.
If moved fast, will turn into a liquid.
Enables rapid movement of skeletal plates.