neuroethology: sound in insects
TRANSCRIPT
Neuroethology:Sound in insects
http://biolpc22.york.ac.uk/404/
References
Young, D (1989) Nerve cells and animal behaviour CUP [1st edition, chapter 7]
Also, chapters in: Carew Behavioral neurobiology Zupanc Behavioral neurobiology
papers are on the webhttp://biolpc22.york.ac.uk/404/cjhe/cricket_singing/insect.htm
What is neuroethology?
approach to analyse neural function in terms of evolutionary advantage
Main points of lecture
Sound transmission is inefficient Insects use sound in a major way Overcoming physical obstacles Modifying
wings for sound production the environment for sound production cuticle to hear
Private communication
About sound
sound is a wave of particle compression and rarefaction
energy (or power) is transferred from sender to hearer
sound gets quieter further away sound has to be discriminated according
to species, context and from random noise
Sound properties
speed c (330 m s-1) wavelength (m) frequency f (Hz, cycles/s)
for 330Hz, wavelength 1m for 3.3kHz, wavelength 0.1m for 33kHz, wavelength 0.01m =
10mm
fc
Power transfer - i
First problem for an insect - for air/water interface about 0.02%
Power transfer - ii
Usually other insect far away -
With distance, power decreases
more bad news for insects!
2
1
d
Power transfer - iii
Usually insects small - sound emitted is dependent
on ratio of insect size / wavelength of sound
Power transfer - iv
if you are smaller than 0.2 * more bad news!
Insects use sound in a major way
Mantids* Grasshoppers/crickets* bugs* beetles* diptera (true flies)* lacewings moths
How do they manage this if physics is so unfavourable?
Overcoming physical obstacles
Resonance Baffle Horn
Sound production Sound reception
Resonance
Mass and a spring; resonant frequency
s is stiffness, m mass below fo in phase; at fo 90o; above fo out
of phase
m
sfo
2
1
Gryllus
Field cricket nice loud
song, carries a long way
attracts females & males
territorial
Gryllus
EMGs
sound
oscillogram
sonogram
Females…
… walk to the loudest sound
Sound made by wing
plectrum
add wax to harp
frequency reduced resonator affected
remove teeth
Gryllus campestris
sound output 60 W muscle work 2 mW efficiency 3%
Can they do any better?
Bush crickets
Higher frequency damped oscillation
Baffle
Bush cricket Oecanthus power *
12
Gryllotalpa
mole cricket
Horn shaped burrow
Gryllotalpa
sound output 1 mW muscle work 5 mW efficiency 20%
Summary so far
Modified wings for sound production Modifying the environment for sound
production
Well done the male crickets!Now onto: what about hearing?
Hearing
locust = grasshopper ears
Tympanum structure
Tympanum structure
Muller’s organ has sensory endings in it
Tympanum (ear drum) taut membrane
side view
top view
Movement
it’s the relative movement which will stretch the axons
Movement
peaks at 3 & 6kHz indicate resonance resonance also shown by phase plot folded body not in phase with membrane
even when at 4kHz amplitude is same relative movement needed to stretch
axons of Muller’s organ
Cricket hearing
acoustic trachea acts like horn for 5kHz sound
Summary so far: Resonance!!
Modified wings for sound production Modifying the environment for sound
production Modified cuticle to hear
Now onto: shh, let’ keep this to ourselves?
Drosophila courtship
Male has black tip
Olfaction
Singing
Detecting vibration
near field sound movement detector aristae - bristles on
antennae
Private communication
Sound movement in dB
since sound is measured on a log scale, 80 << 95
Summary
The neuroethological approach relates the function of the nervous system to its evolutionary advantage
Many insects use sound produce it quite efficiently hear it effectively