Behaviour etc

1
Behaviour etc

• nervous system
• sensory apparatus
• integration
• behaviour - processes and function

2
Nervous system

• insect nerve cells are complex
• insect nerve cells have highest metabolic rate of
  any known tissue
• insect nerve cells respond faster than ours
  (small size of brain)
• insect nerve cells cant send long range pulses
  quickly
• insect nerve cells dont have redundancy

3
(No Transcript)
4
organisation

• 2 ventral nerve chords segmental ganglia
• CNS primitively ladder
• CNS has tendency to become fused
• brain supra- suboesophageal ganglia

5
(No Transcript)
6
(No Transcript)
7
sense organs

• mainly setae many kinds of sensory setae
• mechanosensory, chemosensory etc
• campaniform - cuticular stress
• placoid - chemoreception
• chordotonal organs - limb position
• equilibrium sensors (e.g. Johnsons organ

8
(No Transcript)
9
vision

• ocelli
• stemmata
• compound eyes

10

• ocelli - late instar hemimetabolous insects,
  adult insects fast response, some may detect
  images. Used in horizon detection, flight control
• stemmata - larvae of holometabolous insects.
  Largely light/dark detectors, limited image
  formation
• compound eyes - larvae of hemimetabolous insects,
  adult insects. Used to detect images

11
(No Transcript)
12
(No Transcript)
13
ommatidia organisation

• corneal lens
• crystaline cone - feeds light into rhabdomeres
• rhodopsins oriented in villi of rhabdomeres
• 3 colour (sometimes 4 colour) vision
• UV/blue/green, sometimes red
• detector cells twist, short (UV) cell detects
  polarization

14
apposition compound eyes

• commonest form in insects operating in daylight
• each ommatidium provides information from a
  narrow solid angle about its axis
• axes not oriented radially, some areas densely
  sampled by ommatidia arranged almost parallel
  (fovea)
• complex neural circuitry combines information
  from adjacent ommatidia

15
superposition compound eyes

• mainly nocturnal insects ( (modified) in
  butterflies)
• lens systems of many ommatidia act as little
  telescopes and generate an erect image on the
  retina (made up of the packed detector elements
  of many ommatidia)
• eyes have a clear space and produce eye-shine
• resolution not quite as good as apposition eye,
  light collection 10-100x better

16
muscid eyes

• only found in muscoid flies (houseflies,
  blowflies, tachinids etc)
• apposition eyes BUT detector elements dont twist
  AND detector elements from adjacent ommatidia
  that are looking in the same direction are
  hooked up through a complex nerve mesh
• good light detection capability, good resolution
• associated with need to collect photons to
  compensate for effects of rapid turning flight

17
vision

• extensive neural processing in optic lobe,feature
  detection circuits similar to ours
• motion detection
• image detection
• speed of processing (flies have flicker-fusion
  thresholds gt 5 x ours)

18

• insect vision is a field of very active research
  and ANU is a world leader
• we now know insects are MUCH more capable than
  was thought the case even 10 years ago
• emulation of insect vision is proving a fertile
  field in robotic vision
• other insect senses are likely to prove equally
  impressive

19
behaviour

• navigation
• behaviour/ecology
• development
• maintenance
• mating systems

20
navigation

• use of vision
• landmarks wasp, bee first flights
• use of sun compass
• use of polarization pattern if sun not visible
• time clock to compensate for suns apparent
  movement
• other senses - chemical, remembering steps

21
use of landmarks

• originally investigated in sphecid wasps
• Philanthus work - Tinbergen
• use of landmarks
• availability
• kinds preferred
• hierarchy of landmarks used at different scales
• hierarchy of backups remembered

22
(No Transcript)
23
sun compass

• use position of sun in sky to navigate
• time clock to compensate for suns apparent
  movement (even overnight!)
• enables flight over long ranges or uniform
  habitat (ranges of kms)
• use of polarization pattern in small patches of
  clear sky if sun not visible

24
other senses

• chemical gradients
• magnetic sense
• remembering steps
• REAL navigation almost always involves a
  hierarchy of different senses, with backups

25
behaviour and ecology

• behaviour is a key process underlying ecology
• example we will take dragonfly life
  history(will bounce around a range of species)

26
larval stages

• Diphlebia is the concrete example
• females lay eggs in rotten wood floating in pools
• micro-habitat of earliest larval stages unknown
• later stages occur under rocks in riffles
• emerge at night to hunt prey on rocks

27
adult maintenance

• thermoregulation
• conformers
• heliothermy
• myothermy
• feeding
• prey detection
• interception

28
mating systems

• e.g. dragonflies (very well studied)
• rendezvous, operational sex ratio
• male behaviour
• sperm competition
• female responses to limit interference
• mating in dragonflies requires female action
  males can hold on to encourage - but may lose
  opportunities

29
sperm competition

• Insects preadapted for strong sperm competition -
  sperm stored, only a few used per egg, eggs
  fertilized at laying
• displacement or extraction of previous sperm
• mate guarding to prevent take over by another
  male (with consequent loss of stored sperm)

30
exercise

• examination of dragonfly mating systems

31
References

• Physiology Imms Outlines of entomology as
  revised CSIRO Insects of Australia
• Behaviour navigation, mating systems/sperm
  competitionAlcock Animal behavior an
  evolutionary approach
• dragonflies Corbet Dragonflies behavior and
  ecology of Odonata