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

Model of gull head without dot Cardboard cutout Fake bill – stick with contrasting bars at the end Model of bill alone

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 Video

FAPs can be exploited...

FAPs can be exploited…. video

FAPs can be exploited... 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... 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 room When loud sounds were played, bats navigated perfectly 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

A1 is sensitive to ultrasounds of low-med intensity; A2 produces action potentials only when ultrasound is loud As sound increases, A1 fires more often, with shorter delays A1 fires more frequently in response to pulses of sound than steady sound Response of both A1 and A2 is the same over a broad ultrasound range 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 ear When 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

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 Video

Moths can do more than just evade

Tiger moths produce ultrasonic clicks in response to attacking bats Experiment Trained 3 juvenille and 1 adult big brown bat to capture tethered moths in a flight room On each of the 9 consecutive nights presented: 4 tiger moths 4 tiger moths that were silenced (damage to sound-producing organ) 8 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: 1) approaches the target 2) increases frequency and amplitude of echolocation signals 3) captures prey Video footage shows that clicks led to unusual echolocating behaviour.