Cephalopods

Question 1

cephalopod= “__ and ___”

Answer 1

head and foot

Question 2

cephalopods evolved from:

They have many fossil forms such as _____ and belemnites

Answer 2

benthic shelled mollusc (snail)

ammonites

Question 3

List the groups of cephalopods living today:

give an example of each

Answer 3

1. Nautiloidea (eg nautilus)
2. Coleoidea eg squid
   - Spirulida eg spirula
   - Sepia (cuttlefish)
   - Octopoda (octopus)

Question 4

t/f
all cephalopods have lost their shell (from their gastropod ancestor)

Answer 4

false

shell retained in Nautilus

shell reduced in cuttlefish and squid

shell extended more= belemnites

shell coiled= ammonites

shell loss= octopus

Question 5

Cephalopods are the largest ___ and have very well developed ___ and ___ systems

Answer 5

invertebrates

sensory and nervous

Question 6

Cephalopods have remarkable ___ systems:
- Eyes: ___ and camera eyes
- _____ on skin that can change color and texture

Answer 6

sensory

pinhole

chromatophores

Question 7

Describe the 2 different kinds of eyes that cephalopods can have

Answer 7

1. pinhole eye: no lens, muscles adjust the opening for focus
   - eg nautilus
2. camera eye: les of different density
   eg. octopus

Question 8

camera eyes differ in vertebrates vs in octopus. How? What does this imply?

Answer 8

vertebrate= focus by squeezing the lens, and the eye is an outgrowth of the brain

octopus= focus by moving the lens, and the eye is formed by the skin growing in

this implies that camera eyes have a different developmental origin in each= convergent evolution

Question 9

Why do cephalopods have such complex eyes?

Answer 9

to see food/ predators/ mates

especially octopus who have lost their shell for protection: evolving eyes can help protect them

Question 10

Cephalopods have chromatophores. What are they?

Answer 10

= a pigment cell controlled by nerves

allows rapid color changes for camouflage
- pigment granules are pulled into one spot or expanded to whole cell by a nervous stimulation

Question 11

Cephalopods are ___, but can change their color to anything. We don’t know how!

Answer 11

colorblind

they can also change color of just 1 part of their body

Question 12

There are 2 different types of chromatophores:
1. Iridophores=
2 Photophores=

Answer 12

1. Iridophores= cells that produce metallic shiny color
2. Photophores= bacterial light organs

Question 13

How do cephalopods change the texture of their skin to blend in with surfaces like corals?

Answer 13

they can change the morphology of their skin (not just the color!) using muscles

Question 14

The Hawaiian Bobtail squid is a great model to study ____
Describe how they work in this animal

Answer 14

photophores

The have ‘side pockets’ that get inoculated with Vibrio fischeri bacteria
- at critical population of bacteria- they bioluminescence!
- uses them for country illumination to hunt at night on the reef flats
- hides in the sand in the day time

this is symbiosis!

Question 15

Carnivorous cephalopods:
- have a ___ and chitinous ___ (some are poisonous) with suckers
- they are fast; use jet propulsion with ___ and ____
- have ___ hearts for rapid oxygen exchange
- are agile; most have traded in their ___ for speed

Answer 15

beak, teeth

mantle and siphon

branchial

shells

Question 16

giant nerves in squid aid in rapid contraction of the ___ for ‘jet swimming’

Answer 16

mantle

Question 17

give an example of a detritivore cephalopod. What does it eat?

Answer 17

the vampire squid

It lives in the oxygen minimum zone (~1000m) and eats marine snow

Question 18

cephalopod evolution has been an arms race with ___. Why?

Answer 18

fish
because fish would eat cephalopods!

Question 19

Cephalopod evolution was so successful due to:
- intelligence (development of the __ system)
- ability to get off the ___ (loss of __)
- rapid ___

Answer 19

nervous

bottom, shell

propulsion (jet)

Question 20

How do cephalopods stay buoyant?
- Nautilus vs cuttlefish

Answer 20

gas production and release allows for buoyancy control

Nautilus: chambers (phragmocone) with setae inside, filled with gas from metabolism

Cuttlefish: cuttlebone + osmotic pump

Question 21

What is a siphuncle? What’s its purpose?

Answer 21

In nautilus:
a tube connecting the animal with all gas-filled chambers (tissue has an osmotic pump)

• contains part of the visceral mass (tissues lining the gut)
• cells can absorb water and release gas from metabolism

Question 22

Buoyancy Compensation in Nautilus:

1. As the nautilus grows larger, it builds a new ___ (vacates the last one), and the shell gets ___
2. solutes are ____ transported out of the last chamber into the ____
3. water moves out of the chamber into the ___ by ___
4. Gases (from ___ of the animal) diffuse into the newly empty chamber gradually
   - these gases provide ___ to offset the weight of the new shell

Answer 22

chamber
heavier

actively
siphuncle

siphuncle
osmosis (passive)

metabolism
buoyancy

Question 23

deep sea squid regulate buoyancy using ___

Answer 23

ammonium

Question 24

Explain how cuttlefish stay buoyant

Answer 24

Cuttlebone:
- gas-water exchange occurs with an osmotic pump: change of salt concentration used to move water in and out of cuttlebone

Question 25

t/f

cephalopods do not have separate sexes

Answer 25

false
they do

Question 26

How do cephalopods reproduce?

Answer 26

• often pass sperm sacs into female mantle using a specialized arm
  –> direct egg development in egg cases

many species (like Octopus) brood (for a LONG time)

Question 27

the female octopus broods (guards eggs until they hatch) for up to ___ months!!!

Answer 27

54
they don’t move in that time!

Question 28

female Paper Argonauts are ___ cephalopods that hitch rides on ___, ___, and salps

Answer 28

pelagic

jellyfish, pyrsosomes

Question 29

How do paper argonauts stay afloat?

Answer 29

they secrete a shell with their arms, which is used for buoyancy and for hiding their eggs

Question 30

What is a male paper argonaut like?

Answer 30

miniature!
- one arm develops to deliver sperm and is left in the female’s shell