pramod seminar checked

1

Pleasant Smell

2

Unpleasant Smell

3

Pramod Kumar K.

2010-11-150

Dept. of Agricultural Entomology

4

Can insects be repelled by bad odour ?-

Mechanism of olfaction in insects

Contents

5

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

Conclusion

Olfaction

6

The sense of smell

Distribution of Olfactory Receptors

7

Maxillary palps

(Mosquitoes)8

Olfactory sensilla are present on

Antennae

(Praying mantis)

Labial palps

(Butterfly)

Structure of Olfactory Receptors

9

Cuticular components Cellular components

Cuticular Components

10

Multiporous

Pores accommodate

olfactory receptors

helps in perception of

smell

Different Types of Sensillum

11

Trichoid sensilla

Basiconic sensilla

Coeloconic sensilla

Placoid sensilla

(Chapman, 2006)

Trichoid Sensilla

12

Hair like structures (thin walled or thick walled)

eg. Antennae of Bombyx mori

Basiconic Sensilla

13

Peg or cone like organs

eg. Maxillary palps of female culicidae

Coeloconic Sensilla

14

Cuticular peg is sunk below the general surface of the cuticle.

Opening at surface of

cuticle

Cavity

Peg

Dendrite

Cuticle

Dendrite sheath

Placodea Sensilla

15

Flat or raised in to a slight dome

eg. Antennae of honey bee

Pore

Dendrite

Neuron

Cellular Components

16

Cells of olfactory sensilla are derived from the epidermis

Trichogen cell

Cellular Components contd…

17

Number of sensory neurons in olfactory sensilla

varies from 2 to 20

Male moths Grasshopper

Mechanism of Olfactory Reception

18

Insect Olfactory Sense

19

Odorants (smells/volatile chemicals) have to travel

through pores in the cuticle

Distinctive smell from environments like

semiochemicals

Semiochemicals

Pheromones Allelochemicals

20

Sex pheromone

Aggregation pheromone

Alarm pheromone

Trail pheromone

Allomones

Kairomones

Synamones

Apneumones

(Ragumoorthui et al., 2007)

Pheromone

21

Intraspecific chemical substances that mediate

communication between insects

Ectohormones

1959: Karlson and Butenandt

Silkworm moths

Sex Pheromone

22

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 - helilure

Female Sex Pheromone

Bactrocera dorsalis

23

Methyl eugenol

Female Sex Pheromone contd…

Bactrocera cucurbitae

24

Cuelure

Aggregation Pheromone

25

Pheromones which induce aggregation or

congregation of insects for protection,

reproduction and feeding

Coleoptera and Dictyoptera

Cockroach – periplanone Phloem beetle - ipsenol

Aggregation Pheromone contd…

26

Red palm weevil – Rhynchophorus ferrugenius

Ferrolure

Alarm Pheromone

Chemical substance released by insects to warn

members of same species about the presence or

attack by an enemy

eg. Aphids

27

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. Ants

28

Allelochemicals

29

Interspecific chemicals mediate the communication

between two different species of insects

They are classified in to four categories

Allomones

Chemical released by one insect that induce a

response in another insect

Helpful to emitter

eg. Sting glands in bees

30

Kairomones

Chemical released by one insect that induce a

response in another insect

Helpful to recipient

eg. Heptanoic acid releases by potato tuber moth

31

Synamone

Chemical released by one insect that induce a

response in another insect

Helpful to emitter and receiver

eg. Termites and protozoan's

32

Apneumones

A chemical substance emitted by non living material

that evoke the behavioural or physiological reaction

adaptively for receiving organism

eg. Oat meal oil

33

Insect Attractants

34

Chemicals that cause insect to make oriented

movements towards their source

Types of attractants are

Pheromone

Natural food lures

Natural Food Lures

35

Chemicals present in plant and animal hosts that

attract insect for feeding

Floral scents nectar feeding insect

Decomposing products

Fish Meal Trap

36

Sorghum shoot fly is attracted to rotten fish meal

Coconut shell trap

37

Insect Repellants

38

An oriented movement of insects away from

their source of food

Insect Olfactory Sense contd...

39

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)

Neuron

40

41

Antennae

Sensilla

Na+ , K+ channel

Glomeruli

42

Projection neuronProtocerebrum

Motor neuron

Response

Insect Olfactory Sense contd...

43

OBP

Insect Olfactory Sense contd...

44

Receptor neurons project an axon through the

olfactory nerve into the primary olfactory centers –

olfactory bulb

Insect Olfactory Sense contd...

45

Deutocerebrum

Have the olfactory lobe

Receives signal from

glomeruli

Projection neurons will

send the signal to

protocerebrum

Insect Olfactory Sense contd...

46

Projection neurons, connecting olfactory lobes to

mushroom bodies and other parts of protocerebrum.

Insect Olfactory Sense contd...

47

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 recognized

Olfactometer

48

Specific reaction to olfactory stimuli to be verified by olfactometer responses

Examples for insect repellence by

bad odour

49

(Mandavgane et al., 2005)50

Repelling mosquitoes by burning neem leaves

along with cow dung

51

To repel honey robber, some stingless social beeserect walls of sticky resin in front of or around thenest entrance, while other species smear arepugnant liquid there

(Lett and Kraus, 1994)52

Eucalyptus oil – pleasant smell in human, repellent

effect on insects like mosquitoes and fleas

53

Cocoa leaves, eucalyptus oil, garlic extract, olive

oil mixture of these ingredients will repell the ants,

cockroach, mosquitoes and spiders

54

Osmeterium, an orange, Y-shaped structure on the

neck of caterpillar gives off a strong, unpleasant

odour when it is threatened

55

Conclusion

56

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.

Only odour stimuli in the case of insects. They

receive only those known to them

There is nothing like good or bad odour

57

58