phenotypic plasticity in locusts - panopto

Question 1

phenotype influenced by…

Answer 1

genotype and environment

Question 2

phenotypic plasticity =

Answer 2

animals can change in response to the environment

e.g. behaviour is an example of a plastic trait - learning causes an experience-driven change in behaviour

Question 3

desert locust distribution:

Answer 3

normally live in northern Africa and the Arabia Peninsula

during swarm outbreaks, they erupt outwards of this zone

Question 4

phase change is driven by…

Answer 4

changes in population density

triggered by the sight and smell of other locusts

< 3 per 100m squared = solitarious phase

> 100,000 per 100m squared = gregarious phase

Question 5

solitarious locusts -

Answer 5

isolated (low population density)

repel each other

cryptic colour (camouflage)

slow (less active)

groom infrequently

Question 6

gregarious locusts -

Answer 6

crowding (high population density)

attracted to each other

warning colour (mimic colouration of poisonous insects)

more active/ fast

spend more time grooming

experiments carried out by Ott and Rogers (2010), showed gregarious locusts’ brains are 30% larger - because of the behavioural demands of living in a group with intraspecific competition (need to be more active)

Question 7

locust phase polyphenism:

Answer 7

evolved in adaptation to extreme changes in the availability and distribution of resources

caused solely by presence/absence of other locusts

can be initiated at any time in a locusts life

changes unfold over different time scales:

• behaviour = hours to days
• colour = days to lifetime
• full morphology = several generations

Question 8

both phases can be generated in the lab…

Answer 8

by rearing locusts in isolation or in a crowd, in order to understand proximate mechanisms that drive phenotypic plasticity of behaviour

Question 9

quantifying behavioural phase state:

Answer 9

The behaviour of individual gregarious locusts compared with individual solitarious locusts when presented with a crowd of gregarious locusts (stimulus group) can be observed…

locust raised in isolation:

• were less active
• spend less time grooming
• spent more time further away from the other locusts

Question 10

what sensory inputs drive behavioural gregarisation:

Answer 10

crowding

sight

smell

hind leg touch

Question 11

what changes in the nervous system as a result of these sensory inputs:

Answer 11

newly crowded solitarious locusts show a 9-fold increase in the amount of serotonin in the CNS (thoracic ganglia) - however correlation does not equal causation

neurones that produce serotonin are in metathoracic ganglion in the spinal cord of the locust

this change is transient - there after 4 hours of crowding, gone after 24 hours

Question 12

is serotonin necessary:

Answer 12

serotonin receptor antagonists injected into thoracic ganglia of solitarious locusts show that yes, serotonin is needed for rapid early phase change

Question 13

associative odour-food learning:

Answer 13

Y-maze with unfamiliar odours of vanilla and lemon at either end with artificial food paste associated with each - prefered vanilla

when the vanilla odour is associated with toxic nicotine…

• solitarious locusts will learn to prefer lemon
• gregarised locusts had no memory - still go to vanilla

when the food is then presented without nicotine…

• all locusts will relate lemon odour with good food
• even crowded locusts can learn good food but not poisonous food