Cephalopods

Question 1

where did cephalopods evolve from?

Answer 1

benthic shelled mollusc

Question 2

what are the fossil forms of cephalopods?

Answer 2

ammonites
belemnites

Question 3

what are the 4 living groups?

Answer 3

squid
cuttlefish
spirula
octopus

Question 4

what does coleoidea include?

Answer 4

squid
cuttlefish
spirula
octopus

Question 5

what do nautiloidea include?

Answer 5

nautilus
- only living group

Question 6

shell loss

Answer 6

octopusees

Question 7

shell reduced

Answer 7

cuttlefish
squid

Question 8

shell extended more

Answer 8

belemnites

Question 9

shell coiled

Answer 9

ammonites

Question 10

shell retained in one group only

Answer 10

nautiloids

Question 11

shelled benthic

Answer 11

gastropod

Question 12

what is the story of shell loss

Answer 12

• shelled benthic gastropod
• shell extended became lighter by including septae with gases
• shell retained in one group only
• shell extended more
• shell coiled
• shell reduced
• shell loss

Question 13

serious predators and competitors with fish

Answer 13

ellesmerocerid
- early cephalopod

Question 14

what does cephalopod mean?

Answer 14

head + foot

Question 15

what does the snail foot become?

Answer 15

tentacles/arms and brain/eye

Question 16

the body has a shell secreted by?

Answer 16

a mantel

Question 17

what are the adaptations for?

Answer 17

speed and sensory systems

Question 18

what are cephalopods?

Answer 18

the largest invertebrates

Question 19

describe cephalopods

Answer 19

intelligent with well-developed nervous and sensory systems

Question 20

what is the sensory systems like?

Answer 20

well developed eyes - pinhole and camera eye
chromatophores on skin - change color and texture

Question 21

which species have pinhole eyes?

Answer 21

Nautilus - image forming

Question 22

which species have camera eye?

Answer 22

octopus

Question 23

which species have chromatophores on skin?

Answer 23

mimicry octopus

Question 24

which species have bioluminescent organs?

Answer 24

Euprymna - bobtail squid

Question 25

describe pinhole eyes

Answer 25

no lens
muscles adjust opening of pinhole for focus

Question 26

describe camera eye

Answer 26

lens of different density in octopus

Question 27

how are eyes formed in octopus skin?

Answer 27

grows in skin

Question 28

how are eyes formed in vertebrates?

Answer 28

outgrowth of brain

Question 29

how to octopus eyes focus?

Answer 29

move the lens
- retina is everted

Question 30

how to vertebrate eyes focus?

Answer 30

squeezing lens
- retina in inverted

Question 31

why do cephalopods have complex eyes?

Answer 31

need to see color and changes in color for communication

Question 32

what is the purpose of chromatophores?

Answer 32

communication

Question 33

what controls pigment cells?

Answer 33

nerves allowing rapid color changes

Question 34

iridophores

Answer 34

cells producing metallic shiny color or iridescence

Question 35

photophores

Answer 35

bacterial light organs and change the morphology of their skin using muscles

Question 36

who uses photophores?

Answer 36

Euprymna scolopes - hawaiian bobtail squid
- pockets get inoculated with Vibrio fischeri bacteria
- fluoresce at certain density
- uses them for counter illumination to hunt at night on reef flats
- hides in daytime

Question 37

what kind of predators are cephalopods?

Answer 37

carnivores
- beak and chitinous teeth on suckers - some poisonous

Question 38

describe carnivorous cephalopods

Answer 38

• fast -> use jet propulsion with mantle and siphon
• 2 brachial hearts to push out O2 depleted blood and take in O2 filled blood
• agile - traded in the shell for speed
• giant nerves in squid for rapid contraction of mantle for jet swimming

Question 39

what is an example of a detritivore cephalopod

Answer 39

vampire squid
- Vampyroteuthis infernalis

Question 40

describe their evolution

Answer 40

• arms race with fish
• successful bc of intelligence, ability to suspend, rapid jet propulsion

Question 41

how do Nautilus and cuttlefish become buoyant?

Answer 41

gas production and release

Question 42

how does Nautilus control buoyancy?

Answer 42

chambers called phragmocone

Question 43

how do cuttlefish control buoyancy?

Answer 43

cuttlebone + osmotic pump

Question 44

why can’t Nautilus go super deep the water column?

Answer 44

shell has air so to prevent implosion they cant do past 700m

Question 45

what is a siphuncle?

Answer 45

tube connecting animal with all gas-filled chambers
contains visceral mass which is soft tissue lining the gut
cells absorb water and release gas from metabolism

Question 46

describe buoyancy compensation in Nautilus

Answer 46

• as animal grows larger, builds a new chamber
  -> vacates last chamber
  -> shell gets heavier
• solutes actively transported out of the last chamber into siphuncle
• water moves out of chamber into siphuncle by osmosis passively -> equalize solute concentration
• gases diffuse into newly empty chamber gradually -> gases provide buoyancy to offset weight of new shell

Question 47

describe cuttlefish buoyancy

Answer 47

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

Question 48

how do deep sea squid control buoyancy?

Answer 48

ammonium
- accumulate ammonia in muscle and coelomic cavity

Question 49

reproduction of cephalopods

Answer 49

• separate sexes
• pass sperm sacs into female mantle using specialized arm
• direct development in egg cases
• many species brood eggs
• deep-sea have longest known egg-brooding
• die after laying eggs