Insect physiology : processes and reviews

Physiology of insects ; There behaviour

1. UNIVERSITY OF AGRICULTURAL SCIENCES , Bangalore COLLEGE OF SERICULTURE , CHINTAMANI SUB: Insect Physiology ENT 502(2+1)

2. Presented To: Dr. Arathi pannure Asst. Professor Dept. Of Agril . Entomology College Of Sericulture, Chintamani Presented BY: Punith Kumar S.R PAMC30 08 Jr. M.Sc.(Agri.) Dept,of Agri.Entomology College Of Sericulture, CHINTAMANI

3. INSECT NUTRITION;

4. NUTRITION: Nutrition concerns the chemicals required by an organism for its growth, tissue maintenance, reproduction and the energy necessary to maintain these functions. Many of these chemicals are ingested with the food, but others are synthesized by the insect itself. In some insects, micro- organisms contribute to the insect’s nutrient pool.

5. NUTRITIONAL REQUIREMENTS: Most insects have qualitatively similar nutritional require- ments since the basic chemical composition of their tissues and their metabolic processes are generally similar. Most of these requirements are normally met by the diet. Some chemicals can only be obtained in the diet: they are essential. Others may be synthesized by the insect from dietary components. The dietary requirements of a species may sometimes be obscured due to chemicals having been accumulated and passed on from a previous generation.

6. AMINO ACIDS: Amino acids are required for ; Production of proteins-for structural purposes As Enzymes – for transport and storage As receptor molecules Some involved in morphogenesis. Tyrosine – Cuticular sclerotization Tryptophan – visual screening pigmentats Prolin – Energy source

7. Amino acids are usually present in the diet as proteins. Proteins contain some 20 different amino acids, usually only 10 are essential in diet,and others are derived from these 10.

8. Absence of any one of these prevents growth. Some require additional Amino acids. Example; Proline – development of Culex and Bombyx Aspartic acid and Glutamic acid

9. Alanine and Glycine + Essential Amino acids =Optimal growth of Silkworm Non essential Amino acids comprise over 50% of total amino acids –Optimal growth

10. Synthesis of Non essential Amino acids depends on the ability of insect to make certain chemical structures. Tyrosine – key AA in cuticular sclerotization ,but insects cannot synthesis it’s aromatic ring. Often derived from Phenylalanine Polyphagous Grasshoppers – protocatechuic acid and gallic acid ( phenolic compounds) – cuticular sclerotization Sulfur containing Amino acids are produced from other Amino acids containing sulfur. Methionine = Cysteine , Cystine

11. Amino acids production primarily in Fat bodies but it also occurs in other tissues.

12. CARBOHYDRATES: Insect cuticle have Chitin- Carbohydrate CARBOHYDRATES Fuels FATS AMINO ACIDS CHITIN CARBOHYDRATES

13. Some insects can grow on diet without carbohydrates. Example; Larva of Screw worm fly which feed on Animal tissues. Wax moth which feed on wax.

14. Most of the insects require some amount of carbohydrates in the diet,and grow better as the proportion increased. Example; Optimal at 70% Tenebrio – atleast 40% Schistocerca – atleast 20% of carbohydrates

15. Some insects can use wide range of Carbohydrates because they are capable of digesting the complex structures. Example; Tribolium – Starch Mannitol Trisaccharide - raffinose Disaccharide- Sucrose,Maltose,Cellobiose Various Monosaccharides

16. The grasshopper ( Melonoplus ) – cannot utilize polysaccharides Stem boring larvae of Chilo – utilize only Sucrose, Maltose, fructose and Glucose . Most insects cannot utilize Cellulose and other plant polymers. The larvae of Aedes can use starch and glycogen , but adults cannot .

17. LIPIDS: Fatty acids ,sterols and phospholipids – Components of cellwall Insects can synthesize many fatty acids and phospholipids so they are not usually essential dietiary constituents. Fatty acids present as Diacylglycerides and Triacylglycerides .

18. Anthonomus – Have 23 fatty acids ,but palmitic and oleic acids comprise 60% Polyunsaturated fatty acids with 20 carbon atoms present in phospholipids of many insect species. Derivatives of polyunsaturated fatty acid – Eicosanoids - stimulate oviposition in Crickets reproduction in all insects Thermoregulation Lipid mobilization Immune response of caterpillars to bacteria in hemolymph

19. Cockroach( Periplaneta ) and Cricket ( Acheta ) – can synthesize polyunsaturated fatty acids from dietary acetate Lepodoptera – require linolenic acid in diet Shortage of linolenic acid in diet of Ephestia – moth emerging without scales on wings – scales donot separate from pupal cuticle

20. Larval Mosquitoes – require C20 fatty acids – without them,emerging adults are weak and unable to fly.

21. Sterols : Insects are unable to synthesize sterols. They usually require a sterols in diet. Some obtain from Symbiotic microorganisms. In some insects cholesterol is necessary precursor in synthesis of Ecdysone. Plant feeding insects - Plant sterols – Cholesterol – Ecdysone Animal tissues feeding insects – Cholesterol – Ecdysone

22. Few insects with specialized feeding habits use other sterols , reflecting the absence of cholesterol from their normal food . Examples; Drosophila pachea – Cactus- lophenol and Schottenol Anbrosia beetle( Xyleborus )- Symbiotic fungi – utilize Cholesterol+ ergostrol ( fungal sterols)

23. Fat-soluble Vitamins; ẞ-carotene ( provitamin A) essential in the diet of all insects because it is the functional component of visual pigments It probably also has other functions For example, eggs of Schistocerca - enough ẞ-carotene - growth of the larvae. But deficient in carotene, growth is retarded and the molt delayed. In addition, the insects are smaller and less active than usual. ẞ-carotene is also commonly involved in the normal pigmentation of leaf-eating insects. Without it ,they don’t develop yellow or green colour and Melanization in also reduced.

24. Vitamin E( tocopherol ) ; Reproduction in some insects Improves fecundity in moths and beetles Absence- Halts spermatogenesis in House cricket.

25. Water soluble Vitamins: B Vitamin ; Organic and required in small amounts in diet Function – Cofactors of enzymes Similar 7 such compounds are required in diet. They are: Thiamine,Riboflavin,Nicotinic acid, Pyridoxine, Pantothenic acid ,Folic acid and Biotin. Biotin – component of pyruvate carboxylase in Honeybees Folic acid – Nucleic acid biosynthesis Tenebrio – usual 7 + Carnitine

26. Lipogenic compounds: Myo -inositol and Choline – constituents of phospholipids,Lecithins and phosphatidylinositols Required much larger amounts than Vitamins. In Drosophila- Choline – spermatogenesis and oogenesis Choline provide basis for neurotransmitter,Acetylcholine .

27. Ascorbic acid: Function in not known. Deficiency- Abnormalities at ecdysis , affects the process of cuticular sclerotization Nucleic acid: Most of insects – Donot need Some Diptera : Srew worm , Drosophila , Culex – Do Need Other Diptera - develop faster and less mortality with Nucleic acid in diet.

28. Inorganic Compounds: Sodium , Potassium ,Calcium , Magnesium,Chloride and Phosphate – Essential elements in functioning of cell and essential components of diet Iron – central element of cytochrome Zinc and Manganese - Hardening the cuticle of mandibles

29. Balance of nutrients: Optimal growth requires the nutrient levels to be balanced. Insects feeding on animals- require high amino acids Insects feeding on plants- require equal amounts of amino acids and carbohydrates . Example: Orthoptera , Coleoptera and Lepidoptera

30. Single Amino acids change can cause an affect on growth of insects. Example; Schistocerca gregaria – lettuce – phenylalanine- increase the mass from 82% to 130% Female Aedes – Blood of Guinea pig- 35 eggs/ mg blood - Blood of humans – 24eggs/ mg of blood

31. Nutrients also interact with non- nutrient chemicals in the diet. Example; Phenolic compounds- leaves- reduce digestibility of proteins in caerpillars Nutrients may detrimental to some insects,but it may serve as nutrient for other. Example;Tannic acid – Grass- Grasshoppers

32. Changes in the balance of nutrients: Nutritional requirments of the insects changes with time because of the varying demands of growth, reproduction, diapause or migration. Early larval stages need high Nitrogen than later stages. Example; Larval Gypsy moth : given diet with different levels of protein and lipids

33. Changes may occur within stadium. Example; Cockroach, Supella - higher Carbohydrate intake relative to protein in the first half of larval stadium than in second.

34. Changes of diet based sexual differences. Example; Female Gypsy moth larvae – selects higher protein diet and higher level of nitrogen utilization than male larvae.

35. Female need higher dietary protein than males - egg production. Example; Blood sucking insects (Mosquitoes etc ) Females - Blood feeders- high protein Males – Nectar feeders- less protein

36. Grasshopper, Oedaleus After emerged both sexes - grains and millets( high protein) rather than leaves( less protein) Later, Females- Grains ( high protein) Males – Leaves / Grains

37. Some female Mosquitoes do not lay eggs until they have their first blood meal – Anautogenous Example; Aedes - yolk development –protein from vertebrate blood Others lay first batch of eggs without a blood meal- Autogenous Example; Culex – yolk development – storage protein and from denaturation of flight muscles

38. Maintaining a balance: Insect can respond to a dietary imbalance in 3 ways. Adjust total amount ingested Move from one food to another with different nutrient balance Adjust the efficiency with which it uses the nutrients

39. Grasshopper, Caterpillars and Cockroach – increase the amount eaten – if diet is diluted Example; Melanoplus sanguinipes – diet diluted 7:1 ratio – 7 fold increase in total amount of food Similar behaviour was also seen in Caterpillars of Spodoptera

40. If insects have a choice of foods with different nutrient levels, they regulate their nutrient intake by eating differentially from the foods available. Example; Grasshoppers and Caterpillars – correct previous imbalance of proteins Larval Heliothis – adjust amounts of vitamins and lipids Locusta – maintains both salts and major nutrients

41. The ability to adjust food intake to nutritional requirements implies some feedback. In the Locust, feedback has been shown from hemolymph . High levels of Amino acids – Depress sensitivity of peipheral contact chemoreceptors- Reduce affinity towards amino acids Insects can taste Sugars, Amino acids and Salts. But not proteins ,sterols and vitamins

42. Many insects habitually eat food that is nutritionally inadequate. These insects are able to use these materials through Symbiotic association with micro-organisms.

43. Ectosymbiotic fungi: The insects manipulate the fungus, and so derives nutrients,indirectly from substrates that are difficult to utilize directly. Example; Ambrosia beetles – fungi – use xylem of woody plants ( Fusarium and Ambrosiella ) - Nitrogen and Ergosterol

44. Endosymbionts: Many insects have insects extracellulary in the gut and lumen. Example; Blattodea – Hindgut and fatbody – Bacteria-Carbohydrate digestion and Nitrogen recycling

45. NUTRITIONAL EFFECTS ON GROWTH AND DEVELOPMENT: Variation in quantity or quality of an acceptable diet can have profound effects on insects development. Gain in body size – increase of Nitrogen intake Fod intake decreases - duration of development is extended-insect decomes smaller and lighter in weight

46. Nutritionally poor diet- low Growth – increase number of larval stages. Exmaple ; Spodoptera exempta Panicum and Setaria - grow slowly - 2 additional stage Cynodon - normal growth – pupate at end of 5 th stadium

47. In Mosquitoes,Egg production is proportional to amount nitrogen ingested with blood meal ẞ-carotene is essential constituent of yellow carotenoid

48. Insects differ from eating different quality of food. Example; Caterpillars of spring brood of Nemoria arizonaria – resemble oak catkins – feed on them Yellow Rough cuticle 2 rows reddish spots in midline Smaller head capsule and mandibles

49. Caterpillars of summer brood – resemble stems- feed on leaves Green – grey Without row spots Larger head capsule and mandibles

50. In honeybee,the quality of food given to larvae by workers make them queen or workers.

51. REFERENCES; The Insects ; structure and function , Chapman,R.F