Cephalopods Flashcards
cephalopod= “__ and ___”
head and foot
cephalopods evolved from:
They have many fossil forms such as _____ and belemnites
benthic shelled mollusc (snail)
ammonites
List the groups of cephalopods living today:
give an example of each
- Nautiloidea (eg nautilus)
- Coleoidea eg squid
- Spirulida eg spirula
- Sepia (cuttlefish)
- Octopoda (octopus)
t/f
all cephalopods have lost their shell (from their gastropod ancestor)
false
shell retained in Nautilus
shell reduced in cuttlefish and squid
shell extended more= belemnites
shell coiled= ammonites
shell loss= octopus
Cephalopods are the largest ___ and have very well developed ___ and ___ systems
invertebrates
sensory and nervous
Cephalopods have remarkable ___ systems:
- Eyes: ___ and camera eyes
- _____ on skin that can change color and texture
sensory
pinhole
chromatophores
Describe the 2 different kinds of eyes that cephalopods can have
- pinhole eye: no lens, muscles adjust the opening for focus
- eg nautilus - camera eye: les of different density
eg. octopus
camera eyes differ in vertebrates vs in octopus. How? What does this imply?
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
Why do cephalopods have such complex eyes?
to see food/ predators/ mates
especially octopus who have lost their shell for protection: evolving eyes can help protect them
Cephalopods have chromatophores. What are they?
= 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
Cephalopods are ___, but can change their color to anything. We don’t know how!
colorblind
they can also change color of just 1 part of their body
There are 2 different types of chromatophores:
1. Iridophores=
2 Photophores=
- Iridophores= cells that produce metallic shiny color
- Photophores= bacterial light organs
How do cephalopods change the texture of their skin to blend in with surfaces like corals?
they can change the morphology of their skin (not just the color!) using muscles
The Hawaiian Bobtail squid is a great model to study ____
Describe how they work in this animal
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!
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
beak, teeth
mantle and siphon
branchial
shells
giant nerves in squid aid in rapid contraction of the ___ for ‘jet swimming’
mantle
give an example of a detritivore cephalopod. What does it eat?
the vampire squid
It lives in the oxygen minimum zone (~1000m) and eats marine snow
cephalopod evolution has been an arms race with ___. Why?
fish
because fish would eat cephalopods!
Cephalopod evolution was so successful due to:
- intelligence (development of the __ system)
- ability to get off the ___ (loss of __)
- rapid ___
nervous
bottom, shell
propulsion (jet)
How do cephalopods stay buoyant?
- Nautilus vs cuttlefish
gas production and release allows for buoyancy control
Nautilus: chambers (phragmocone) with setae inside, filled with gas from metabolism
Cuttlefish: cuttlebone + osmotic pump
What is a siphuncle? What’s its purpose?
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
Buoyancy Compensation in Nautilus:
- As the nautilus grows larger, it builds a new ___ (vacates the last one), and the shell gets ___
- solutes are ____ transported out of the last chamber into the ____
- water moves out of the chamber into the ___ by ___
- Gases (from ___ of the animal) diffuse into the newly empty chamber gradually
- these gases provide ___ to offset the weight of the new shell
chamber
heavier
actively
siphuncle
siphuncle
osmosis (passive)
metabolism
buoyancy
deep sea squid regulate buoyancy using ___
ammonium
Explain how cuttlefish stay buoyant
Cuttlebone:
- gas-water exchange occurs with an osmotic pump: change of salt concentration used to move water in and out of cuttlebone
t/f
cephalopods do not have separate sexes
false
they do
How do cephalopods reproduce?
- 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)
the female octopus broods (guards eggs until they hatch) for up to ___ months!!!
54
they don’t move in that time!
female Paper Argonauts are ___ cephalopods that hitch rides on ___, ___, and salps
pelagic
jellyfish, pyrsosomes
How do paper argonauts stay afloat?
they secrete a shell with their arms, which is used for buoyancy and for hiding their eggs
What is a male paper argonaut like?
miniature!
- one arm develops to deliver sperm and is left in the female’s shell
