Class Cephalopoda

Question 1

What are some characteristics of their lifestyle?

Answer 1

• active
• pelagic
• predatory

Question 2

What are some molluscan characteristics of cephalopods? (4) Are any modified?

Answer 2

1. Have Radula
2. Ctenidium (but is non-ciliated)
3. Shell-secreting mantle (but reduced or lost in most extant species)
4. The foot

Question 3

Distinctive characteristics of Nautiloids (2)

Answer 3

1. Septate shell

2. Modified foot

Question 4

What is the septate shell?

Answer 4

Heavily calcified external shell internally divided by septal partitions (has many internal chambers)

Question 5

How is the foot modified?

Answer 5

1. Prehensile appendages on anterior end (arms/tentacles)

2. Funnel (where water escapes mantle cavity)

Question 6

How do we know the tentacles and funnel were derived from the foot?

Answer 6

Nerves from pedal ganglia innervate arms and tentacles

Question 7

What are the 3 subclasses?

Answer 7

Nautiloidea
Ammonoidea (extinct)
Coleoidea

Question 8

How are the tentacles of Nautilus distinct?

Answer 8

No suckers

Question 9

Do they use their air chambers to undergo diel-vertical migration?

Answer 9

No. Manipulating air: fluid ratio WOULD alter buoyancy BUT takes too long

Question 10

How do they undergo diel-vertical migration?

Answer 10

Muscular contraction of the muscle (brings water into mantle cavity and jets out)

Question 11

What are the internal separations of a nautiloid shell? What fills these with gas?

Answer 11

1. Septa

2. Siphuncle->tubes that runs in between shell perforations

Question 12

What have squids lost? How has this changed their mantle?

Answer 12

• have lost shell

- mantle has become extremely muscular

Question 13

How are the appendages modified in squids?

Answer 13

• Appendages in form of 8 shorter arms and 2 longer tentacles
• Tentacles have suckers only at tips

Question 14

How do squids they do gas exchange?

Answer 14

• muscular pumping of mantle cavity pumps water in

- water enters mantle cavity on either side of head, pass past gill filaments and out funnel

Question 15

How do fast vs slow contraction of the mantle cavity cause differences in the motion of the squid?

Answer 15

Fast: jet propulsion locomotion by jetting water out funnel
Slow: just for breathing

Question 16

How is water sucked into the mantle?

Answer 16

Radial muscle contraction expands the volume of the mantle cavity to create negative pressure (and seawater sucked in on either end)

Question 17

What type of predators are squids?

What feature enables this?

Answer 17

• Visual predators

- Image-forming eyes

Question 18

What are 4 features of the circulatory system?

Answer 18

• Closed (capillary beds)
• systemic and branchial hearts
• high pressure for rapid circulation to deliver oxygen to tissue

Question 19

Other molluscs vs cephalopods circulatory system

Answer 19

1. Cephalopods have branchial, systemic hearts and capillaries
2. Others have only 1 heart and interconnected haemal spaces

Question 20

What does the high metabolic rate of squids require? (3)

Answer 20

• ventilation of gills by muscular pumping of mantle
• closed circulatory system (capillary beds)
• branchial/systemic hearts

Question 21

How do cephalopods change colour?

Answer 21

Chromatophores
-contract to look more white and expand to colour themselves
Reflectors to display dif colours of light

Question 22

What is unique about the flamboyant cuttlefish?

Answer 22

• toxic venom

- aposematic colour warning

Question 23

How does cephalopod reproduction work?

Answer 23

• average lifespan is ~1yr
• lay eggs on substrate
• no free-swimming larval stage