precise presentation about insect integument added with its utilty in pest management strategies

1. INTEGUMENT AND ITS ROLE IN PEST
MANAGEMENT
Presented by:
K.A.Sindhura
Ist year M.Sc(Entomology)
Anand Agricultural University, Anand
1

2. INTRODUCTION
 The integument or body wall of insects is the outer layer of its body
comprising of the epidermis.
 Consists of:
 Basement membrane
 Epidermis (Hypodermis)
 Cuticle
 Cuticle is a characteristic of Phylum Arthropoda.
 Cuticle plays a crucial role in insect survival and dominance.
2

3. FUNCTIONS OF INTEGUMENT
 Composed of Chitin –Strong, rigid, and flexible
 Provides large area for muscle attachment
 Conserves water, minimizes water loss and hence prevents
desiccation.
 Prevents mechanical injury.
 Protective coloration.
 Act as a tool for various activities like digging, oviposition, and
preying.
 Gives physical strength without making the insect body heavier.
3

4. STRUCTURE AND CHEMISTRY OF
INTEGUMENT
4

5. STRUCTURE OF INTEGUMENT
 The outer covering of insects is referred to both as an exoskeleton
and an integument.
 The integument consists of
 Inner basement membrane
 Middle epidermal cell layer – epidermis (or hypodermis)
 Non-living outer cuticle.
5

6. STRUCTURE OF INSECT INTEGUMENT
6

7. Structure of the Integument
 Basement membrane: a continuous sheet of
mucopolysaccharide, as much as 0.5 mm in thickness;
initially secreted by haemocytes.
 Epidermis: the only living portion of the integument;
modifications of these cells produce dermal glands, sensory
receptors and their support cells, and oenocytes.
7

8.  Cuticle: secreted by epidermis; divided into two
main regions:
 Epicuticle:
 consists of cement layer, wax layer, polyphenol layer,
and the cuticulin layer.
 This is the outermost, thinnest cuticular layer devoid of
chitin.
 Procuticle:
 Inner cuticular layer consists of exocuticle, mesocuticle,
and endocuticle, constituted largely of chitin and
protein.
8

9. The Epicuticle
 The epicuticle is a complex layer consisting of several
layers that are produced by both the epidermal cells and
dermal glands.
 Cement layer:
 Consists mostly of lipoprotein secreted by dermal glands (Verson’s gland in
Lepidoptera).
 Functions as a varnish, provides protective external surface to integument.
 Prevents water loss from the body
 Absent in honey bees.
cont.
9

10.  The wax layer :
 0.25 microns thick
 Contains hydrocarbons with 25-31 carbon atoms, alcohols of 24-34 carbon
atoms, and esters of fatty acids.
 produced by the epidermal cells.
 Act as a waterproof layer of the integument as it contains tightly packed wax
molecules.
 The Polyphenol layer :
 Non-static layer
 composed of polyhydric phenols.
 Phenols are transported from epidermal cells through the pore canals and
are accumulated on the outer surface of the cuticulin layer.
cont.
10

11.  Cuticulin layer:
 Refractile layer.
 Amber coloured.
 Consist of a lipoprotein – Cuticulin
 Highly resistant to mineral acids and most organic solvents.
 Serves as a permeability and growth barrier
 Determines the surface properties of integument
11

12. The Chitinous cuticle (Procuticle)
 The procuticle is secreted by the epidermal cells and
consists largely of chitin and protein.
 exocuticle: the proteins become heavily cross-linked and
insoluble; are not broken down during the molting cycle;
pigments deposited within it
 endocuticle: synthesis continues after the old cuticle is shed,
often in daily layers; cross-linking is reduced; completely broken
down during molting process
 mesocuticle: as a transitional layer in which the proteins are
untanned like the endocuticle but impregnated with lipid and
proteins like the exocuticle
12

13. Features of Procuticle
 Lamellar organization :
 Chitin microfibrils lie parallel to each other ,form a group of layers about 20-250A° thick.
 Due to lamellar architect, the endocuticle becomes much elastic and provides flexibility
and stretching properties of the integument.
 Pore canals:
 Are very fine structures measuring about 0.15 to 1 microns and runs perpendicular to the
direction of chitin microfibrils.
 In newly synthesized cuticle, they follow spiral courses and contain cytoplasmic filaments
 In matured cuticle, they become straight and contain cuticular substances.
 Functions to transport cuticular substances from epidermal cells to upper surface of
procuticle.
 Number of porecanals vary from15,000 per mm² in Sarcophaga to 1,20,000 per sq. mm in
Periplaneta .
cont.
13

14. PORE CANAL ARRANGEMENT IN THE CUTICLE
14

15. PORE CANAL - LONGITUDINAL VIEW
15

16.  Chitin – Protein Microfibrils : Chitin and protein are crucial elements of
arthropods forming major constituents of bodywall.
 In insects they form the framework of cuticle and also constituents of
peritrophic membrane of gut.
Chitin :
Nitrogenous polysaccharide named by Odier (1823).
Made of long chains of acetylated glucosamine residues -- N-Acetyl
glucosamine (C8H13O5N)n
Adjacent chains are held together by β –glycosidic linkages.
16

17. N-acetyl-D-
glucosamine
glucosamine
1-4 b-linkage
CHITIN MOLECULAR
STRUCTURE
17

18.  Protein : Proteins are of 3 types:
Arthropodin : Water-soluble protein found in the endocuticle.
Untanned, elastic protein.
Resilin: Rubber-like protein occurs as colourless cuticular ligament
such as wing-hinge ligament, clpeo-labral suture, etc. Elastic in
nature.
Sclerotin: Tanned protein. Occurs in the exocuticle. It is in fact
tanned athropodin formed by the action of phenol oxidase on the
terminal N group of amino acids forming cross links.
18

19.  Lime :
 In some aquatic insects, lime or CaCO3 is deposited and may form a
major constituent of exocuticle.
 Pigments :
 The insect cuticle posses various pigments such as melanin,
carotenoids, pterins (pigment which gives fluorescent color to
butterfly wings).
19

20. CHEMISTRY OF CUTICLE
 The insect cuticle is composed largely of
 Proteins
 comprise more than half the dry weight of the insect cuticle.
 Primarily distributed within the Procuticle.
 Synthesized mainly by epidermal cells
 Chitin
 Consisting of 20-40% of the total dry weight of the cuticle.
 Polymer of N-acetyl-D-glucosamine.
 Synthesized by epidermal cells
 Lipids
 Mainly located in the wax layer of epicuticle
 Synthesized largely by the Oenocytes and the fat body 20

21. 21
BIOSYNTHESIS OF CHITIN

22.  Synthesis of chitin and deposition of cuticle in insects is regulated by harmones and
mediated by enzymes which catalyse a series of complex biotransformation starting
with glucose/trehalose and ending with chitin formation.
 CHITIN SYNTHATASE is key enzyme in chitin formation whereas CHITINASE and
CHITOBIOSE are key enzymes in degradation.
 Any interference in chitin synthesis and degradation can lead to interruption of
metamorphosis and growth of organism.
 Compounds that interfere with chitin biosynthesis exert toxic effects at time of
moulting.
 This has lead to extensive research into chitin synthesis inhibitors as agents for
insect control.
22

23. Role in insect management
CHITIN SYNTHESIS INHIBITORS:-
 Discovered by scientists of Philips Duphar who were trying to discover some super herbicide in 1972.
 First commercialized compound was DIFLUBENZURON marketed as DIMILIN.
 Many Benzoyl phenyl ureas like
diflubenzuron,teflubenzuron,triflumuron,novaluran,flucyclouran,plant origin compounds like
plumbagin,azhadirachtine,Synthetic pyrethroid like permethrin and natural compounds like
polyoxins and nikkomycins from micro organisms Streptomycine cacoi and Streptomycin tendae
respectively.
 Used against coleopteran,diptera,hemiptera and Lepidoptera.
 Act as larvicide.
23

24. Mechanism of action:-CSI act by interrupting the synthesis or transport of specific
proteins that are required for assembly of chitin protein network to form laminated
cuticle.
 Nikkomycins and polyoxins are acting as competitive inhibitor of chitin synthetase
enzyme.
 They block the active site of enzyme and UDP-NAG cannot bind to then active site
to undergo polymerization.
Advantages:-
 Safe to the mammals and other non target animals due to absence of chitin in their
body system as compare to synthetic chemicals.
 Safe to non target and beneficial insects as their activities are growth stage
specific,being mostly larvicidal in action i.e, they are safe to predators as most of
these are active in adult stage.So these can be better fitted as one of the IPM
component.
24

25.  Degradation in environment is faster than synthetic pesticides,so less pollutant to the
environment.
 These can be used in insecticide resistance management due to different mode of
action.
 No phytotoxicity is exhibited.
 Potentially can be incorporated in the forestry,horticultural,houshold and storage pest
control where quick action is not required.
Disadvantages:-
 Very slow in action.
 It limits its action only at the time of moulting.
 They cannot kill all the pest population in the field as pest population generally
comprises all the growth stages(egg/larva/pupa/adult) and these are mostly active
against larval stage.
25

26. Dessicant insecticides:-
1.Diatomaceous Earth:-
 It is naturally occurring,soft,chalk-like sedimentary rock that crumbles into a light fine powder and has
abrasive effect.
 Its compose of 86% silica,5% sodium, 3% magnesium and 2% iron.
 It consists of fossilized remains of diatoms, a type of hard-shelled algae.
Mechanism of action:- The fine powder absorbs lipids from the waxy outer layer of insects cuticle,causing them
to dehydrate.
Uses:-In the control of grain storage,cockroach,silverfish
Disadvantages:- Health risk to humans and benefcial insects.
26

27. 2.Coal Fly Ash:-
 It is waste from coal/lignite based thermal plants and its been explored for pest control by then
Prof.P.Narayanaswamy,Faculty of Agriculture,Annamalai University,Annamalainagar,Tamil Nadu.
Mechanism of action:-
 Wears out mandibles in mouthparts of the insects.
 Cause aberration in insect cuticle and destroys insect body organs and tissues
 Induces insect resistance in plant like Rice
 Activity is manly due to content silica at 50-62%
Uses:-
 Acts as dust insecticide,kills caterpillars,beetles,grasshoppers ,aphids and sucking pests like plant
hoppers and leaf hoppers in crops like Rice,Tomato,Okra,Cauliflower,Oil seeds an Stored grain
 Used as termiticide
 Used as carrier in formulations like Dust,Granules and WP
27

28. CONCLUSION
 The integument serves to be a reason which enable insects to thrive on a
variety of habitats.
 It protects the insect from mechanical injuries, desiccation, and
predators.
 It also aids in some of the behavioral patterns of the insect like digging,
oviposition, etc.
 Any compound interfering in the biosynthesis of chitin can be use as an
inhibitors
 This lead to research on dessicants,CSI and Coal fly ash.
28

29. REFERENCES
 Chapman,R.F. 1982. The Insects – Structure and function. Macmillian India Ltd.,Bangalore.
501-528
 Tembhare,D.B. 2015. Modern Entomology. Himalaya Publishing House,Mumbai. 13-20
 Bharpoda,T.M, Borad,P.K, Thumar,R.K, and Patel,C.C. 2014. Insect Morphology, Anatomy
and Systematics. Asian Printary, Ahmedabad. 11p
 Raghavaiah, G. 2011. Insect Morphology and Systematics course materials, ANGRAU.
 D.S.Reddy-Applied Entomology
 B.Vasantharaj David,V.V.Ramamurthy-Elements of Economic Entomology.
29