Pramod seminar checked


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This is my PG seminar. Dept of Agricultural entomology.

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Pramod seminar checked

  1. 1. 1
  2. 2. Pleasant Smell2
  3. 3. Unpleasant Smell3
  4. 4. Can insects be repelled by bad odour ?- Mechanism of olfaction in insects Pramod Kumar K. 2010-11-150 Dept. of Agricultural Entomology4
  5. 5. Contents  Definition  Distribution of olfactory receptors  Structure of olfactory receptors  Cuticular components  Cellular components  Mechanism of olfaction  Semiochemicals  Insect attractants  Insect Repellants  Examples for insects repellence  Conclusion5
  6. 6. Olfaction  The sense of smell6
  7. 7. Distribution of Olfactory Receptors7
  8. 8.  Olfactory sensilla are present on Antennae (Praying mantis) Labial palps Maxillary palps8 (Butterfly) (Mosquitoes)
  9. 9. Structure of Olfactory Receptors  Cuticular components  Cellular components9
  10. 10. Cuticular Components  Multiporous  Pores accommodate olfactory receptors helps in perception of smell10
  11. 11. Different Types of Sensillum  Trichoid sensilla  Basiconic sensilla  Coeloconic sensilla  Placoid sensilla11 (Chapman, 2006)
  12. 12. Trichoid Sensilla  Hair like structures (thin walled or thick walled) eg. Antennae of Bombyx mori12
  13. 13. Basiconic Sensilla  Peg or cone like organs eg. Maxillary palps of female culicidae13
  14. 14. Coeloconic Sensilla  Cuticular peg is sunk below the general surface of the cuticle. Opening at surface of cuticle Cavity Peg Dendrite Cuticle Dendrite sheath14
  15. 15. Placodea Sensilla  Flat or raised in to a slight dome eg. Antennae of honey bee Pore Dendrite Neuron15
  16. 16. Cellular Components  Cells of olfactory sensilla are derived from the epidermis  Trichogen cell16
  17. 17. Cellular Components contd…  Number of sensory neurons in olfactory sensilla varies from 2 to 20 Male moths Grasshopper17
  18. 18. Mechanism of Olfactory Reception18
  19. 19. Insect Olfactory Sense  Odorants (smells/volatile chemicals) have to travel through pores in the cuticle  Distinctive smell from environments like semiochemicals19
  20. 20. Semiochemicals Pheromones Allelochemicals  Sex pheromone  Allomones  Aggregation pheromone  Kairomones  Alarm pheromone  Synamones  Trail pheromone  Apneumones (Ragumoorthui et al., 2007)20
  21. 21. Pheromone  Intraspecific chemical substances that mediate communication between insects  Ectohormones  1959: Karlson and Butenandt  Silkworm moths21
  22. 22. Sex Pheromone  Pheromone released by one sex only and trigger behaviour patterns in the other sex that facilitate in mating  Female insect produce pheromone eg. Pink bollworm – gossyplure Helicoverpa armigera - helilure22
  23. 23. Female Sex Pheromone Bactrocera dorsalis Methyl eugenol23
  24. 24. Female Sex Pheromone contd… Bactrocera cucurbitae Cuelure24
  25. 25. Aggregation Pheromone  Pheromones which induce aggregation or congregation of insects for protection, reproduction and feeding  Coleoptera and Dictyoptera Cockroach – periplanone Phloem beetle - ipsenol25
  26. 26. Aggregation Pheromone contd…  Red palm weevil – Rhynchophorus ferrugenius  Ferrolure26
  27. 27. Alarm Pheromone  Chemical substance released by insects to warn members of same species about the presence or attack by an enemy eg. Aphids27
  28. 28. Trail Pheromone  Pheromones laid in form of intermittent or continuous lines on a soil substrate which trail followers perceive to reach their destination which could be a mate or food source eg. Ants28
  29. 29. Allelochemicals  Interspecific chemicals mediate the communication between two different species of insects  They are classified in to four categories29
  30. 30. Allomones  Chemical released by one insect that induce a response in another insect  Helpful to emitter eg. Sting glands in bees30
  31. 31. Kairomones  Chemical released by one insect that induce a response in another insect  Helpful to recipient eg. Heptanoic acid releases by potato tuber moth31
  32. 32. Synamone  Chemical released by one insect that induce a response in another insect  Helpful to emitter and receiver eg. Termites and protozoans32
  33. 33. Apneumones  A chemical substance emitted by non living material that evoke the behavioural or physiological reaction adaptively for receiving organism eg. Oat meal oil33
  34. 34. Insect Attractants  Chemicals that cause insect to make oriented movements towards their source  Types of attractants are  Pheromone  Natural food lures34
  35. 35. Natural Food Lures  Chemicals present in plant and animal hosts that attract insect for feeding  Floral scents nectar feeding insect  Decomposing products35
  36. 36. Fish Meal Trap  Sorghum shoot fly is attracted to rotten fish meal36
  37. 37. Coconut shell trap37
  38. 38. Insect Repellants  An oriented movement of insects away from their source of food38
  39. 39. Insect Olfactory Sense contd...  Smell travels through air  Then they diffuse and are carried by an odorant binding protein (OBP)  Many odorants are received by insect olfactory sensillum and perceived by the olfactory receptor neurons (ORNs) (Galizia and Rossler, 2010)39
  40. 40. Neuron40
  41. 41. Sensilla Antennae Na+ , K+ channel Glomeruli41
  42. 42. Protocerebrum Projection neuron Response42 Motor neuron
  43. 43. Insect Olfactory Sense contd... OBP43
  44. 44. Insect Olfactory Sense contd...  Receptor neurons project an axon through the olfactory nerve into the primary olfactory centers – olfactory bulb44
  45. 45. Insect Olfactory Sense contd... Deutocerebrum  Have the olfactory lobe  Receives signal from glomeruli  Projection neurons will send the signal to protocerebrum45
  46. 46. Insect Olfactory Sense contd...  Projection neurons, connecting olfactory lobes to mushroom bodies and other parts of protocerebrum.46
  47. 47. Insect Olfactory Sense contd...  The physiological characteristics of the projection neurons vary  They respond only when the antennal receptors are simulated by a specific odour like a pheromone, attractant or repellent components  Others are simply ignored or not recognized47
  48. 48. Olfactometer  Specific reaction to olfactory stimuli to be verified by olfactometer responses48
  49. 49. Examples for insect repellence by bad odour49
  50. 50. Repelling mosquitoes by burning neem leaves along with cow dung50 (Mandavgane et al., 2005)
  51. 51. To repel honey robber, some stingless social bees erect walls of sticky resin in front of or around the nest entrance, while other species smear a repugnant liquid there51
  52. 52. Eucalyptus oil – pleasant smell in human, repellent effect on insects like mosquitoes and fleas52 (Lett and Kraus, 1994)
  53. 53. Cocoa leaves, eucalyptus oil, garlic extract, olive oil mixture of these ingredients will repell the ants, cockroach, mosquitoes and spiders53
  54. 54. Osmeterium, an orange, Y-shaped structure on the neck of caterpillar gives off a strong, unpleasant odour when it is threatened54
  55. 55. 55
  56. 56. Conclusion  Odour perception is like visiting a library. Thousands of books are present in the library. Similarly there are a number of odorants present in the environment. All groups of insects have specific odours which they receive through specific glomeruli.56
  57. 57.  Only odour stimuli in the case of insects. They receive only those known to them  There is nothing like good or bad odour57
  58. 58. 58