Cephalopods cognition brain size and structure Flashcards
What is a cephalopod?
Invertebrates in the phylum mollusca.
Describe the cognition of a cephalopod.
- Highly organised.
- Well distributed throughout the body.
- Individual decisions are made.
- Cognition is driven by them being both a predator and prey.
Describe the life history of cephalopods.
- There are 4 main groups: cuttlefish, squid, nautilus and octopus.
- All marine species.
- Some are pelagic like squid (live in the open ocean), some are benthic like octopus (live on the ocean floor).
- Have planktonic larvae.
- Only reproduce once and adults die after reproduction.
- Short life span of 2 years maximum.
- Not social.
Describe the ecology of cephalopods.
- They are prey to many animals.
- They are predatory.
- They have a soft body and show cryptic behaviour for protection and hunting. This is when they change their colour and texture.
- They have behavioural adaptations as well as flexible colourations.
Describe the morphology of cephalopods.
All:
- 8 legs which are muscular hydrostats.
- Have suckers on the legs which also act as chemoreceptors.
- Large eyes and an excellent visual system.
- Octopus have beaks.
- Squid and cuttlefish have ‘bones’ for rigidity.
- Nautilus have shells.
What are chromatophores?
These are pigment sacs surrounded by neurons which can be dynamically changed in size.
- They are found in each cell.
- They form the defence mechanism of a cephalopod as they allow for camouflage and colour changes.
How do chromatophores form the defence system?
They can be controlled consciously or unconsciously.
- Expansion of the pigment sac causes more pigment to be see, and this allows for camouflage.
How is ‘camouflage’ done in the open ocean?
Iridophores reflect light differently to change the appearance of cephalopods.
Describe the nervous system of cephalopods.
- Have a central lobe, visual lobes and 8 lots of peripheral neural systems to control the 8 legs.
Neural tissue:
- 2/5 = central brain.
- 3/5 = throughout the body.
- Approx 530 million neurons.
- Have a system to control chromatophores.
- Organised non-topologically.
What is the distribution of neural tissue like?
There is a heavy input from the skin, legs and PNS.
How are the 8 legs controlled?
Both through conscious and un-coordinated localised control.
What is the degrees of freedom problem in the legs?
- Each leg is not centralised.
- This means there is no overall monitoring of where each leg is.
How do the legs communicate with each other?
Communication is done neurologically.
- Via the interbrachial commisure.
- This is similar to crossing over of left and right side of the brain in humans.
What are ‘fake joints’?
These are formed to simplify control program.
- This is when the legs stiffen up so that objects can be carried easier.
What are constraints faced and how are they tackled?
- No colour vision.
- > They have w shaped cones which allow spectral discrimination (they can match colours).
- No social learning as generations don’t overlap (die after reproduction).
What are key points of their learning?
- Learn quickly.
- Respond contextually so show flexible learning.
- Balance risk of predation with risk of starvation.
Describe the cognition of a cephalopod.
- Flexible.
- Causal reasoning (cause and effect).
- Imagination.
- Show foresight and figure out how to reach their goal.
Describe an experiment used to test cephalopod problem solving.
- Octopus is put in a tank which has a perspex barrier with a hole large enough for one leg to fit through.
- Food is put in a feeding tube which is also in the tank.
- The perspex barrier is changed to an opaque layer to see how the situation is manipulated to get food.
- Then the feeding position is changed to see how the octopus gets food.
The innate tendency to pull must be overcome, as the food is not always reachable by pulling; problem solving must be done.
What was the success rate on each different situation?
All were completed and food was reached, but time differed: no perspex < clear perspex < opaque perspex < changed feeding position.
What is tactical deception in cuttlefish?
Males deceiving other males during mating by selectively displaying courtship signs.
- This is possible as male and female cuttlefish are coloured differently.
- Females are mottled brown and males have zebra stripes.
What was seen when testing tactical deception in cuttlefish?
- Males only showed zebra stripes when they were courting a singe female and another male was close.
- The changed appearance was done in a way that it was oriented to the female, i.e. half facing female is striped, half facing rival male is mottled brown.
Why was it tested if octopus play?
It was thought that play is limited to mammals and birds.
How was play tested in octopus?
- They were given Lego and observed if exploration was done or if play was done.
What is the difference between exploration and play?
Play is spontaneous and voluntary and lasts longer than exploratory events.
What was observed?
- 9/14 showed low level play with non-food Lego items.
- 1/14 showed high level play with non-food Lego items.
- The age of octopus had no effect.
Therefore, octopus do play.
How is foresight seen in veined octopus?
- These octopus carry coconut shell halves to use as protection.
- They carry it for future use, which shows foresight/prospection.
What are the evidences for their cognition points?
- Behavioural flexibility - tactical deception, push/pull experiment and tool use.
- Causal reasoning - generalising a solution in the push/pull experiment.
- Imagination - play.
- Foresight - tool use.
How is cognition in cephalopods comparable to that in mammals and birds?
- Many of the same kinds of cognitive abilities are present despite different anatomy.
What further research must be done in cephalopods?
- Do more studies, not just in octopus.
- Compare the found abilities to their need in the wild.
- Determine how information is processed between legs.
- Determine what drives the cognitive sophistication: flexible anatomy or constraints of their niche.
