Cephalopods Flashcards
where did cephalopods evolve from?
benthic shelled mollusc
what are the fossil forms of cephalopods?
ammonites
belemnites
what are the 4 living groups?
squid
cuttlefish
spirula
octopus
what does coleoidea include?
squid
cuttlefish
spirula
octopus
what do nautiloidea include?
nautilus
- only living group
shell loss
octopusees
shell reduced
cuttlefish
squid
shell extended more
belemnites
shell coiled
ammonites
shell retained in one group only
nautiloids
shelled benthic
gastropod
what is the story of shell loss
- 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
serious predators and competitors with fish
ellesmerocerid
- early cephalopod
what does cephalopod mean?
head + foot
what does the snail foot become?
tentacles/arms and brain/eye
the body has a shell secreted by?
a mantel
what are the adaptations for?
speed and sensory systems
what are cephalopods?
the largest invertebrates
describe cephalopods
intelligent with well-developed nervous and sensory systems
what is the sensory systems like?
well developed eyes - pinhole and camera eye
chromatophores on skin - change color and texture
which species have pinhole eyes?
Nautilus - image forming
which species have camera eye?
octopus
which species have chromatophores on skin?
mimicry octopus
which species have bioluminescent organs?
Euprymna - bobtail squid
describe pinhole eyes
no lens
muscles adjust opening of pinhole for focus
describe camera eye
lens of different density in octopus
how are eyes formed in octopus skin?
grows in skin
how are eyes formed in vertebrates?
outgrowth of brain
how to octopus eyes focus?
move the lens
- retina is everted
how to vertebrate eyes focus?
squeezing lens
- retina in inverted
why do cephalopods have complex eyes?
need to see color and changes in color for communication
what is the purpose of chromatophores?
communication
what controls pigment cells?
nerves allowing rapid color changes
iridophores
cells producing metallic shiny color or iridescence
photophores
bacterial light organs and change the morphology of their skin using muscles
who uses photophores?
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
what kind of predators are cephalopods?
carnivores
- beak and chitinous teeth on suckers - some poisonous
describe carnivorous cephalopods
- 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
what is an example of a detritivore cephalopod
vampire squid
- Vampyroteuthis infernalis
describe their evolution
- arms race with fish
- successful bc of intelligence, ability to suspend, rapid jet propulsion
how do Nautilus and cuttlefish become buoyant?
gas production and release
how does Nautilus control buoyancy?
chambers called phragmocone
how do cuttlefish control buoyancy?
cuttlebone + osmotic pump
why can’t Nautilus go super deep the water column?
shell has air so to prevent implosion they cant do past 700m
what is a siphuncle?
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
describe buoyancy compensation in Nautilus
- 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
describe cuttlefish buoyancy
gas-water exchange occurs with osmotic pump
- change salt concentration used to move water in and out of cuttlebone
how do deep sea squid control buoyancy?
ammonium
- accumulate ammonia in muscle and coelomic cavity
reproduction of cephalopods
- 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
