physiology of behaviour - module recap

• Crabs were more likely to respond to a dummy predator if:

  •the predator model approached them in a straight line

  •the crab was further away from the burrow

  •the dummy predator was higher
• Crabs were also sensitive to


  Dummy predator's speed

  Dummy predator's vertical expansion
• crabs process visual information through four nested retinotopic neurophils

  Lamina

  Medulla

  Lobula

  Lobula plate
• Two classes of lobula giant neurons

  Monostratifed lobula giant 1 and 2 : MLG1 and 2
• Lobula giant neurons are:

  motion sensitive and are likely involved in the regulation of run speed and direction
• MLG1 involved in


  early phases of the escape and code information on the position of the predator
• MLG2 involved when


  predator is close
• Azimuth


  position in horizontal plane
• Elevation 


  position in the vertical plane
• Two kinds of cues:

  Intensity cues and timings cues
• Intenstity cues


  sound elevation - interaural level difference
• To accurately localise sounds in space, owls must compute two aspects

  its azimuth and its elevation
• Timing cues


  to determine a sound's azimuth
• reference of owls


  Kdudson and Konishi
• Four classes of units indentified in the mid-brian auditory area of owls

  Limited-field unit

  Complex-field unit

  Space-preferring unit

  Space-independent unit
• Researchers also indentified the neural circuits responsible for the ITD:

  This circuit includes the magnocellular cochlear nucleus, that code for the timing of the sound and the nucleus laminaris that computes the ITD
• Place cells


  active when individual passes through a specific location
• Grid cells


  active when an animal traverses one of the vertices of a periodic hexagonal or triangular lattice that tiles the environment
• Border cells


  active when the animal is located along one or several borders of the environment
• Head-direction cells


  active when the head is in a specific direction relative to the environment
• types of cells reference

  Geva-Sangiv et al., 2015
• Findings from a bat-tunnel study

  Place-cells have multiple place fields

  Cells had very large place fields (up to 32m) and very small ones (<1m)

  Many place cells showed highly variable field sizes
• Compositions of ions and water in extra and intra cellular fluid is carefully controlled
• cells need


  water for virtually all metabolic processes and as a solvent but it is lost through different body functions
• Osmosis is


  a spontaneous movement of water through a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration
• Phenomenon affects


  water retention and dispersion in different taxa depending on the environment they live
• Unicellular marine organisms à rely on seawater to provide them with all nutrients, O2, water, and electrolytes (e.g. Na+, K+, Cl-) to sustain life processes à essentially, the evolution of more complex multicellular organisms has required compartmentalisation of “seawater” within the body (i.e. extracellular fluid).

  Two main components of ECF.
• Presence of waterproof substances (lipids, mucus) on skin to prevent


  water dispersion
• Key anatomical adaptions


  development of large storages of water

  reduction of sweat glands

  development of countercurrent heat exchanger

  changed in nephron structure to limit or increases water loss

  increase/reduction in appendages (ears and nose) to limit or promote water loss
• Key behaviour adaptations

  Using shelters during hottest periods of the day

  Being inactive when temperatures are high

  Hibernation and aestivation
• energy balance =

  energy intake - energy expenditure
• Energy intake is influenced by several hormones

  insulin, leptin, ghrelin, NYY
• Energy expenditure depends on by

  body size, activity levels, growth rate, reproductive state and environmental stress
• Strategies to cope with food scarcity

  reduction of metabolic rate

  reduction in body temperature

  reduction in physical activity

  reduction in reproduction

  reduction in gastrointestinal tract
• Predator and anti-predator behaviours

  Strategies used by prey to avoid predators
• Predator avoidance in crabs

  • Crabs were more likely to respond to a dummy predator if: the predator model approached them in a straight line; the crab was further away from the burrow; the dummy predator was higher
  • Crabs were also sensitive to: Dummy predator's speed; Dummy predator's vertical expansion
• Physiological experiments on crabs

  1. Crabs process visual information through four nested retinotopic neuropils: Lamina, the medulla, the lobula, and the lobula plate

  2. Two classes of lobula giant neurons (monostratified lobula giant 1 and 2; MLG1 & 2) are motion sensitive and are likely involved in the regulation of run speed and direction

  3. MLG1 involved in early phases of the escape and code information on the position of the predator

  4. MLG2 involved when predator is close
• Azimuth


  Position in horizontal plane
• Elevation


  Position in the vertical plane
• Cues used by owls to locate prey

  • Intensity cues (sound's elevation-interaural level difference) and timing cues (horizontal location-interaural time difference)
  • They need both ears to accurately locate both cues