This is my PG seminar. Dept of Agricultural entomology.
Text of Pramod seminar checked
2. Pleasant Smell2 3. Unpleasant Smell3 4. Can insects be repelled by bad odour ?-Mechanism of olfaction in insectsPramod Kumar K. 2010-11-150 Dept. of Agricultural Entomology4 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. Olfaction The sense of smell6 7. Distribution of Olfactory Receptors7 8. Olfactory sensilla are present on Antennae(Praying mantis)Labial palps Maxillary palps8(Butterfly)(Mosquitoes) 9. Structure of Olfactory Receptors Cuticular components Cellular components9 10. Cuticular Components Multiporous Pores accommodateolfactory receptorshelps in perception ofsmell10 11. Different Types of Sensillum Trichoid sensilla Basiconic sensilla Coeloconic sensilla Placoid sensilla11(Chapman, 2006) 12. Trichoid Sensilla Hair like structures (thin walled or thick walled)eg. Antennae of Bombyx mori12 13. Basiconic Sensilla Peg or cone like organseg. Maxillary palps of female culicidae13 14. Coeloconic Sensilla Cuticular peg is sunk below the general surface ofthe cuticle. Opening at surface of cuticle Cavity Peg Dendrite Cuticle Dendrite sheath14 15. Placodea Sensilla Flat or raised in to a slight dome eg. Antennae of honey beePoreDendriteNeuron15 16. Cellular Components Cells of olfactory sensilla are derived from theepidermis Trichogen cell16 17. Cellular Components contd Number of sensory neurons in olfactory sensillavaries from 2 to 20 Male moths Grasshopper17 18. Mechanism of Olfactory Reception18 19. Insect Olfactory Sense Odorants (smells/volatile chemicals) have to travelthrough pores in the cuticle Distinctive smell from environments likesemiochemicals19 20. Semiochemicals PheromonesAllelochemicals Sex pheromone Allomones Aggregation pheromone Kairomones Alarm pheromone Synamones Trail pheromone Apneumones (Ragumoorthui et al., 2007)20 21. Pheromone Intraspecific chemical substances that mediatecommunication between insects Ectohormones 1959: Karlson and Butenandt Silkworm moths21 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. Female Sex PheromoneBactrocera dorsalis Methyl eugenol23 24. Female Sex PheromonecontdBactrocera cucurbitae Cuelure24 25. Aggregation Pheromone Pheromones which induce aggregation or congregation of insects for protection, reproduction and feeding Coleoptera and DictyopteraCockroach periplanone Phloem beetle - ipsenol25 26. Aggregation Pheromone contd Red palm weevil Rhynchophorus ferrugenius Ferrolure26 27. Alarm Pheromone Chemical substance released by insects to warnmembers of same species about the presence orattack by an enemyeg. Aphids27 28. Trail Pheromone Pheromones laid in form of intermittent orcontinuous lines on a soil substrate which trailfollowers perceive to reach their destination whichcould be a mate or food source eg. Ants28 29. Allelochemicals Interspecific chemicals mediate the communicationbetween two different species of insects They are classified in to four categories29 30. Allomones Chemical released by one insect that induce a response in another insect Helpful to emittereg. Sting glands in bees30 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. Synamone Chemical released by one insect that induce a response in another insect Helpful to emitter and receivereg. Termites and protozoans32 33. Apneumones A chemical substance emitted by non living materialthat evoke the behavioural or physiological reactionadaptively for receiving organismeg. Oat meal oil33 34. Insect Attractants Chemicals that cause insect to make orientedmovements towards their source Types of attractants are Pheromone Natural food lures34 35. Natural Food Lures Chemicals present in plant and animal hosts thatattract insect for feeding Floral scents nectar feeding insect Decomposing products35 36. Fish Meal Trap Sorghum shoot fly is attracted to rotten fish meal36 37. Coconut shell trap37 38. Insect Repellants An oriented movement of insects away fromtheir source of food38 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. Neuron40 41. SensillaAntennae Na+ , K+ channelGlomeruli41 42. Protocerebrum Projection neuron Response42Motor neuron 43. Insect Olfactory Sense contd... OBP43 44. Insect Olfactory Sense contd... Receptor neurons project an axon through theolfactory nerve into the primary olfactory centers olfactory bulb44 45. Insect Olfactory Sense contd... Deutocerebrum Have the olfactory lobe Receives signal from glomeruli Projection neurons will send the signal to protocerebrum45 46. Insect Olfactory Sense contd... Projection neurons, connecting olfactory lobes tomushroom bodies and other parts of protocerebrum.46 47. Insect Olfactory Sense contd... The physiological characteristics of the projectionneurons vary They respond only when the antennal receptors aresimulated by a specific odour like a pheromone,attractant or repellent components Others are simply ignored or not recognized47 48. Olfactometer Specific reaction to olfactory stimuli to be verified by olfactometer responses48 49. Examples for insect repellence by bad odour49 50. Repelling mosquitoes by burning neem leaves along with cow dung50(Mandavgane et al., 2005) 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. Eucalyptus oil pleasant smell in human, repellent effect on insects like mosquitoes and fleas52 (Lett and Kraus, 1994) 53. Cocoa leaves, eucalyptus oil, garlic extract, olive oil mixture of these ingredients will repell the ants, cockroach, mosquitoes and spiders53 54. Osmeterium, an orange, Y-shaped structure on the neck of caterpillar gives off a strong, unpleasant odour when it is threatened54 55. 55 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. Only odour stimuli in the case of insects. Theyreceive only those known to them There is nothing like good or bad odour57 58. 58