Phenotypic plasticity
– Animals can change in response to changes in their environment.
– Behaviour is one (very plastic) aspect of the phenotype.
Learning = experience-driven change in behaviour,
= phenotypic plasticity
Solitarious phase of locus
Behavior: Shy, avoid other locusts, slow movement, dispersed.
Morphology: Dull-colored, smaller body size.
Physiology: Low metabolic and reproductive rates.
Ecology: Minimal impact on crops.
Gregarious phase
Behavior: Highly social, form large swarms, increased activity.
Morphology: Brightly colored, larger body size, strong wings.
Physiology: High metabolic and reproductive rates.
Ecology: Devastates crops, major agricultural threat.
Trigger: Population density and tactile stimulation (e.g., crowded conditions).
Why does locus phase Polyphemus occur
-evolved in adaptation to extreme and unpredictable changes
in the availability and distribution of resources.
-sole direct driver is the presence / absence of other locusts.
-can be initiated at any time during the life of a locust.
-changes unfold over very different time scales e.g. changes in behaviour can occur from hours to days etc.
How to quantify the Behavioural phase state
Solitarious and gregarious locusts differ in multiple behavioural characters.
It’s a behavioural syndrome so there’s difference ranges e.g. autism high functioning and ,ow functioning
- we can see the behaviour in the behaviour arena .
- can have extreemly solitarious and low its a range between the two extremes
What are the sensory inputs drive behavioural gregarisation? ( make little locus go from solitarious phase to gregarious phase)
- crowding
-sight and smell
-hind leg touch
Can measure
Serotonin in thoracic ganglia
- freshly crowded solitarious locus show a 9-fold increase in the amount of serotonin in the CNS.
- only in the thoracic ganglia not the brain
-there is a correlation .
-has behavioural effects e.g. increases social interactions
Metaplasticity
It means an animal’s ability to change can itself change based on experience or environment.
Is plasticity itself plastic? → Yes, it can increase or decrease over time.
Are some animals more plastic? → Yes, those in changing environments adapt more.
check simis notes for gapsin the end
Associative learning in locusts:odour-food conditioning
- The Basic Setup
Locusts are exposed to odors—vanilla and lemon.
They usually prefer vanilla when untrained.
Researchers can train them by pairing an odor with a negative stimulus—in this case, nicotine, which they dislike.
- What Happens During Training?
Solitarious Locusts (live alone, not in a swarm):
Initially prefer vanilla.
After one exposure to vanilla + nicotine, they learn quickly.
Next time, they avoid vanilla and prefer lemon, remembering the bad experience.
Their memory is long-term—they retain this association.
They show immediate aversion based on taste alone, even without getting sick. Their learning is fast and cautious.
Gregarious Locusts (live in swarms):
Also initially prefer vanilla.
After exposure to vanilla + nicotine, they do not immediately change behavior.
They only avoid vanilla after they actually get sick from it.
This is called post-ingestive aversive memory—they have to feel the negative effects before changing.
They don’t mind the taste right away, so learning is slower and experience-based.
- Recently Gregarised Locusts (solitarious locusts crowded for 24 hours):
These are in transition between solitarious and gregarious states.
Despite being crowded, they still act like solitarious locusts in some ways but don’t learn or remember well.
Their behavior is not stable yet, and they don’t yet show either type of learning clearly.
Different individuals take different amounts of time to fully change their behavioral type.
Why?
Solitarious Locusts Fast aversive learning (avoid bad food quickly) Learn from taste immediately to avoid toxic food.
Gregarious Locusts Slow aversive learning (delayed avoidance) Learn from post-ingestive feedback (realizing food is bad later).
Newly Gregarized No aversive memory (forget previous food learning) Likely to match the swarm’s feeding behavior.
laern the specific stduy simis notes
Proximate explanations,
ultimate explanations.
In locusts, solitarious phase involves fast aversive learning to avoid toxins, relying on taste to quickly detect harmful food, which aids survival. In the gregarious phase, learning is slower, with locusts depending on post-ingestive feedback after consuming food, allowing them to take in more food despite potential toxins. Newly gregarized locusts show no immediate aversive learning, as both taste and feedback mechanisms are suppressed, reflecting their focus on group dynamics rather than individual toxin avoidance. These differences help balance costs and benefits related to food intake and survival.
Method of quantifying the behavioural phase state in locusts
Behavioral Tracking (500 s):
The behavior of 100 solitarious and 100 gregarious locusts is tracked over a period of 500 seconds.
Behavioral metrics such as movement speed, direction changes, and proximity to other locusts are recorded.
Logistic Regression Model:
A logistic regression model is used to analyze the behavioral data.
This model provides a single quantitative measure called P
greg for each locust.
Pgreg -represents the probability that an individual locust is behaving in a gregarious phase.
Values range between 0 and 1:
P(_{\text{greg}} = 0:** purely solitarious behavior.
P(_{\text{greg}} = 1: fully gregarious behavior**.
