Neuronal and hormonal control of behaviour

BIOL 3100

Why is this bee making sweet lovin’ to John Alcock’s thumb?

Tinbergen noticed that chick feeding behaviour in gulls is highly ritualized. - chicks peck at the red dot on the gull’s bill

- parents regurgitate food - chicks get fed

The question is: How close must the stimulus be to initiate the begging behaviour?

video

Cardboard cutout

Model of bill alone

Model of gull head without dot Fake bill –

stick with contrasting bars at the end

Sign stimulus (releaser): a signal from one individual to another

Sensory messages from the releaser are processed by innate releasing mechanisms (neuronal clusters) higher in the nervous system

Fixed action pattern: A pre-programmed series of movements that constitute an adaptive reaction to the releasing stimulus

Tinbergen’s Geese

Video

Greylag geese will automatically scoop and retreive eggs that roll <1m from the nest

However, will also roll back anything roughly resembling an egg

If the egg is removed while the goose is in the process of rolling it back, the action will continue

FAPs can be exploited...

FAPs can be exploited….video

Tongue orchids mimic the pheremone by Lissopimpla excelsa wasps

Wasps land on the flower, expecting to find a mate, but instead find a flower structure that looks like a female wasp – which is close enough for the male wasp

Pollen is then stuck to the wasp and transferred to the next tongue orchid

FAPs can be

exploited...

FAPs can be exploited...Alcon butterfly larvae smell almost exactly like the larvae of two ant species (Myrmica rubra, and M. ruginodis). Ant workers will retreive the butterfly larvae and bring them back to the next, where the other workers will feed and protect the butterfly.

Not surprisingly, the story gets more complicated...

What are the neural mechanisms that underlie Fixed Action Patterns?

• The use of ultrasound by bats wasn’t discovered until the 1930s

• Donald Griffin suggested bats may use ultasonic echoes to detect prey

• Designed an experiment where he hung prey were hung on strings in a room with obstacles all around a dark roomo When loud sounds were played, bats

navigated perfectlyo When bombarded with ultrasound,

bats began to collide with obstacles and crash to the floor, until the sound was turned off.

• Kenneth Roeder realized that moths may also be able to hear in the same frequency of bats to avoid being eaten

- Noctuid moths have two ears, one on each side of the thorax- Each ear has a thin cuticle, or tympanum lying over a chamber on the

side of the thorax- Two neurons (A1 and A2) are attached to the tympanum, which are

deformed when the sound pressure waves hit the moth (and hence the tympanum)

- A1 and A2 receptors work like neurons – respond to energy in stimuli by changing the permeability of their cell membranes to positively charged ions

- For moths, movement of the tympanum is the stimulus, which mechanically stimulates the receptor cell

- Once channels in the cell membrane are opened, positively charged ions flow in, changing the charge inside the cell relative to the outside

- If the movement of ions is large enough, an abrupt local change in the electrical charge difference across the membrane occurs and spreads to neighboring portions of the membrane sweeping around the cell and down the axon, creating an action potential – the signal that one neuron uses to communicate with another neuron

1) A1 is sensitive to ultrasounds of low-med intensity; A2 produces action potentials only when ultrasound is loud

2) As sound increases, A1 fires more often, with shorter delays

3) A1 fires more frequently in response to pulses of sound than steady sound

4) Response of both A1 and A2 is the same over a broad ultrasound range

5) No response to low-frequency sounds that we can hear

How moths locate bats in space

When the bat is to one side of the moth, A1 on the side closer to the predator fires sooner and more often than the shielded A1 in the other earWhen the bat is above the moth, A1 fluctuates synchronously with wing beats

When the bat is behind the moth, both A1 receptors fire at the same rate and time

Video

Normally, a praying mantis holds is forelegs close to the body (top left), but when it detects ultrasound, it extends its forelegs (bottom left), causing it to loop and dive down. Lacewings (right) also use an anti-interception dive when detecting ultrasound

Moths can do more than just evade

• Tiger moths produce ultrasonic clicks in response to attacking bats

• Experimento Trained 3 juvenille and 1 adult

big brown bat to capture tethered moths in a flight room

oOn each of the 9 consecutive nights presented:o4 tiger mothso4 tiger moths that were silenced

(damage to sound-producing organ)

o8 wax moths, which do not emit ultrasonic clicks

• If the clicks act as a warning signal (venemous, unpalatable), bats should capture moths then drop them, then later abort attacks

• If bats are startled, they should habituate

• If clicks are a jamming defense, they should deter bat attacks when emitted, but that’s it

• Bats contacted wax moths 400% more often than clicking tiger moths

• Tiger moths without clicks were eaten each time they were encountered

• Contact rates with clicking moths did not change throughout the experiment (thus, no learning or habituation)

• Usually when brown bats capture prey:o 1) approaches the targeto 2) increases frequency and amplitude of

echolocation signalso 3) captures prey

• Video footage shows that clicks led to unusual echolocating behaviour.