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Chemical Signals: Types, Production, and Reception

Explore the world of chemical signals, from hormone production to pheromone transmission. Learn about olfactory receptors in insects and vertebrates, and discover how animals detect and orient themselves through scent trails. Gain insights into diffusion rates, active spaces, and the complexities of odor reception processes.

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Chemical Signals: Types, Production, and Reception

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  1. Chemical Signals • Types • Production • Transmission • Reception

  2. Olfactory signal features • Directionality • Generally propagate away, but rarely linear • Transmission speed • Depends on diffusion rates, wind speeds • Temporal pattern • Difficult to turn on and off • Spectrum • Multi-dimensional

  3. Chemical signals • Hormone • Chemical signals used within individuals • Produced by endocrine glands • Pheromone • Chemical signals used between conspecifics • Produced by exocrine glands • Allomone • Chemical signals used between species

  4. Pheromone examples Diffusion rate is inversely related to molecule size. Small compounds are volatile. Large compounds can persist

  5. Odor glands in mammal skin

  6. Vertebrate glands

  7. Scent dissemination strategies

  8. Female marking by greater spear-nosed bats

  9. Multi-modal signalling in sac-winged bats

  10. Scent glands in ants

  11. Diffusion of a scent puff K = threshold of detection, rA = active space, t = time

  12. Active space is dynamic There is a maximum size of active space which is set by the detection threshold and amount of odorant released

  13. Media affects transmission Q = number of molecules released K = detection threshold D = diffusion rate

  14. Diffusion from a trail Treat as if there are a series of single emissions from a moving source

  15. Diffusion in laminar flow

  16. Diffusion in turbulent flow

  17. Moth active space in wind

  18. Insect odor receptor organs

  19. Insect olfactory sensilla

  20. Vertebrate odor receptor organs Vomeronasal organ detects steroid hormones in urine

  21. Olfactory receptor cell Olfactory receptor proteins have 7 trans-membrane domains, but belong to a gene family with over 1000 loci. Receptor cells Are short-lived (< 60 d), and express a single protein. creates odor-topic map in olfactory bulb

  22. Gradient detection and orientation • Simultaneous sampling • Requires paired olfactory receptors at sides of body. • Need wide head or nose on appendage (antenna) • Sequential sampling • Animals follow concentration gradient, requires tracking back and forth across trail.

  23. Moth scent tracking Animals follow concentration gradient, requires tracking back and forth across trail. Some have paired olfactory receptors at sides of body.

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