Echinoderms

Question 1

What is the general size for echinoderms?

Answer 1

<1cm to 1m for star fish and up to 3m for sea cucumbers

Question 2

What type of symmetry do echinoderms have?

Answer 2

Pentamous radial symmetry

Question 3

Which stages are benthic and pelagic?

Answer 3

Larvae are pelagic and adults are benthic

Question 4

Do they have a heart?

Answer 4

No

Question 5

What is the endoskeleton made up of?

Answer 5

CaCO3 and MgCO3

Question 6

What is the asteroidea?

Answer 6

Tube feet

Question 7

What is the function of the asteroidea (tube feet)?

Answer 7

• Locomotion
• Attachment
• Food manipluation
• Photo reception at the end of foot

Question 8

How do the tube feet move?

Answer 8

Muscles are contracted and fluid is moved in the lumen of the tube foot

Question 9

What are the two stomachs called?

Answer 9

Cardiac and Pyloric

Question 10

What is the function of the cardiac stomach?

Answer 10

Can be everted during feeding and secretes enzymes and the dissolved organism can then be ingested

Question 11

What is the function of the pyloric stomach?

Answer 11

It is either used to send partially digested food to the pyloric ceca for further digestion, or is sent to the rectum for excretion

Question 12

Describe the process of hunched feeding over prey items.

Answer 12

• Shell is prised open by 1mm (5 to 10 minutes)
• Force pull of 3kg
• Cardiac stomach is then pushed into the shell, digestion begins

Question 13

How long can the digestion process take?

Answer 13

4-6 hours depending on prey size