Olfaction in Bats
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Bats use their sense of smell to locate food sources like fruit. While most bats are insectivorous, some eat fruit and have evolved distinctive olfactory receptor genes to detect relevant odors. Bats have two chemosensory systems - olfaction in the nose and vomeronasal detection in the mouth - but many bat species have lost function in the latter system. The evolutionary loss and retention of chemosensory systems varies across bat families and species.
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Olfaction in Bats
- 1. Olfaction in Bats by Liliana M. Dávalos Natural History of the Senses AMNH, 5 November 2018
- 3. Energy flows upward But cannot be fully recovered
- 4. Food is more abundant At lower trophic levels
- 5. Lower trophic level, more species A consistent finding across groups Dumont, Dávalos et al. 2012 Proc Royal Soc B
- 6. Most bats are insectivorous How to detect plant foods?
- 7. Experimental visualization of two interacting odor plumes (red and blue) in a turbulent flow Credit: J. Crimaldi and M. Soltys
- 8. Photo by Carlos Mancina
- 9. Photo by Carlos Mancina
- 10. Bats use their sense of smell to find fruit Thies et al. 1998 Behav Ecol Sociobiol SearchExploreApproach
- 11. Olfactory sensory neurons (in green) transfer information to olfactory projection neurons (in yellow). Credit: J. McGann and M. Wachowiak
- 12. Olfaction happens in th brain Arthropod model more tractable 2005 PLoS Biol
- 13. Perception begins with receptors Mammalian olfactory receptor model embedded in a biological membrane Model by Claire de March
- 14. Receptors bind to volatile molecules After binding, the receptors activate a switch that starts mental representation of odor Model by Claire de March volatile volatile volatile
- 16. A typical example of evolution Single-copy gene (Understanding Evolution site)
- 18. Olfactory receptor genes are arranged in arrays Physical maps of OR functional genes and pseudogenes in several genomic clusters Niimura & Nei 2003 PNAS
- 20. Diverse odors = diverse receptors As a result OR genes make up ~5% of protein- coding genoms Tan et al. 2013 PNAS
- 21. Source Odorants Receptors Receptors reflect diversity of odorants Each receptor is encoded by one OR gene
- 22. Rat Odorants Volatile Organic CompoundsOR genes Ecology Mate Risk Food Food
- 23. But olfactory gene evolution is hard to study • Data collection • Requires high- quality genomes • Expensive! Niimura et al. 2018 Mol Biol Evol
- 24. To get DNA sequences Requires combining technologies
- 25. OR genes vary by species But there are so many how to analyze? Species OR 1/3/7 OR 2/13 OR 5/8/9 Myo$s lucifugus 15 2 0 74 24 55 89 26 55 Anoura geoffroyi 38 7 26 91 30 48 129 37 74
- 26. Reduce dimensions From many gene subfamilies and numbers to two dimensions
- 27. If related to fruit eating One or more dimensions should differ in frugivores compared to others Photo by Carlos Mancina
- 28. Frugivores differ Have more OR gene copies in subfamilies 1/3/7 and 2/13 Hayden et al. 2014 Mol Biol Evol
- 29. Bats and fruit Bats use olfaction to locate fruit and have distinctive genes to encode relevant receptors Photo by Merlin Tuttle
- 30. Neuweiler 2000 Biology of Bats
- 31. The vomeronasal A whole other chemosensory system Neuweiler 2000 Biology of Bats Neuweiler 2000 Biology of Bats
- 32. Did you ever wonder why? Dogs smell hierarchy and sexual condition
- 34. Most bats have atrophied vomeronasal (top) Bhatnagar & Meisami 1998 Mic Res & Tech
- 35. Diversity of bats not fully studied Almost 1400 species described as of last week!
- 38. A first assessment A couple of independent losses Zhao et al. 2010 Mol Biol Evol
- 40. There is more than TRPC2
- 41. Vomeronasal receptors help recognize species (mice) If similar in bats then we should see gene expansions
- 42. Sorex araneus Erinaceus europaeus Canis familiaris Felis catus Equus caballus Vicugna vicugna Bos taurus Tursiops truncatus Pteropus vampyrus Pteropus alecto Rousettus aegyptiacus Hipposideros armiger Rhinolophus ferrumequinum Rhinolophus sinicus Megaderma lyra Miniopterus natalensis Eptesicus fuscus Myotis lucifugus Myotis davidii Myotis brandtii Pteronotus parnellii Desmodus rotundus (genome) Desmodus rotundus Glossophaga soricina Carollia brevicauda Sturnira ludovici Sturnira lilium Artibeus fraterculus Eulipotyphyla Carnivora Perissodactyla Artiodactyla Chiroptera Order Species Trpc2 Intact V1rs Pseudo V1 ψ ψ ψ ψ ψ ψ * * * * * * * * * * * 44 39 6 17 30 22 40 0 0 0 0 2 0 1 1 6 0 0 0 0 3 14 8 2 1 4 4 7 80 84 28 79 48 36 43 33 21 23 18 18 22 22 17 3 3 1 2 3 19 2 -- -- -- -- -- -- V1r numbers taken from the values in the supplement (not adjusted) of Young, et al. (2010) therefore may be an underestimate as genome assemblies have improved. ψ * Trpc2 is intact; Trpc2 is a pseudogene. See (Zhao et al. 2011; Yohe et al. 2017) for refere A few receptors in each case Instead of gene expansion Yohe et al. In Review
- 44. Vomeronasal in bats Is conserved but does not expand, not likely involved in species recognition Neuweiler 2000 Biology of Bats Neuweiler 2000 Biology of Bats
- 45. Thank you!