ENTOM 305- Animal Health Entomology (Lect. 5- Digestive, Excretory & Nervous System)
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Insects feed on either...
- - solids or liquids
- - plant carbohydrates or animal protein
Insects feed on solids...
- - herbivores (locusts, caterpillars) feed on plant carbohydrates
- - carnivores (mantids, ground beetles) feed on animal protein
Insects feed on liquid...
- - sap feeders (aphids) feed on plant carbohydrates
- - blood feeders (fleas, stable flies) feed on animal protein
- - scavengers (cockroaches, mosquitos) feed on both plant carbohydrates and animal protein
Insect digestive system consists of 3 major sections __________ plus __________
- 1.) foregut
- 2.) midgut
- 3.) hindgut
- Plus the salivary glands and their enzymes
- - extends from the mouth to the end of the proventriculus
- - lined with a layer of cuticle (intima) which is shed with each molt
- - cuticle serves as mechanical protection & prevents movement of certain molecules through the gut lining
Insect salivary glands
- - contains digestive enzymes
- - some also secrete silk (caterpillars & Hymenoptera)
- - some also secrete anticoagulants (blood feeders)
- - some also secrete antimicrobial factors (blowfly larvae)
- - midgut extends from the stomodeal valve to the proctodeal valve (derived from endoderm & not lined by cuticle, absorbing lots of nutrients)
- - the midgut (ventriculus) is the main site of digestion & absorption of food
- - gastric caecum secrete proteinases & peptidases to break proteins into amino acids; amylases & carbohydrases to break down carbs; lipases to break down fats
- - peritrophic membrane encloses the food but is permeable to enzymes & nutrients (it is secreted by epithelial cells & made of chitin in a protein-carbohydrate matrix
- - extends from pyloric valve to anus
- - functions in resorption of H20, salts & amino acids & in some cases...
- - pheromone production (fruit flies)
- - respiration (dragonfly gills)
- - fermentation chamber (termintes)
- - derived from ectoderm & lined with cuticle= little absorption
- - consists of anterior hindgut (ileum & colon) & posterior hindgut (rectum)
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