insect digestive systems. insect digestive system developmentally 1 2 3 1. foregut (stomatodeum) -...
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INSECT DIGESTIVE SYSTEMS
Insect Digestive System
Developmentally
12
3
1. Foregut (stomatodeum) - ectodermal
2. Hindgut (proctodeum) - ectodermal
3. Midgut (mesenteron) - endodermal
cuticle
FOREGUT MIDGUT HINDGUT
pharynx
esophagus
crop
Malpighian tubulessalivary glands
cibarium
salivariumgastric caeca
proventriculus
pylorus
ileum
rectum
ventriculus
anus
Variation in insect guts
What does the digestive system do?
1. Obtaining food
2. Mechanically breaks good down into smaller particles that facilitate the activity of digestive enzymes.
3. Enzymatic breakdown of larger food molecules into molecules that can enter the hemolymph.
4. Produce molecules that coordinate feeding and other digestive activities
Salivary Glands
Salivary Glands
Two types
1. Acinous (alveolar) – multicellular with sac-like units-directly innervated from CNS
Subesophageal ganglion
Produces dopamine for fluid secretion
Stomatogastric NSProduces seratonin for enzyme production
2. Tubular – not directly innervated- seratonin from hemolymph to regulate enzyme production
Functions of Salivary Glands
1. Moisten food
2. Lubricate mouthparts
3. Contains digestive enzymes
3a. Amylase – complex sugars to simple sugars
3b. Salivary enzymes for preoral digestion
4. Non-digestive functions
4a. Toxins of predators that affect CNS of prey
4b. Counter toxins of plant allelochemicals
4c. Anti-coagulants
4d. Silk production
Insect Saliva - Composition
e.g. Mosquito saliva
- 20 polypeptides
> 70 unique proteins
Insect Saliva – Composition - changes
Prates et al, 2008. J. Med. Ent 45:409
Lutzomyia longipalpis
Insect Saliva – Composition - changes
Prates et al, 2008. J. Med. Ent 45:409
Lutzomyia longipalpis
Salivary Glands
Aphid Blood feeders
Silk cocoons Plant galls
Salivary glands are involved in disease transmission
ForegutCicada (Homoptera)
pharynx
esophagus
crop
Malpighian tubulessalivary glands
cibarium
salivariumgastric caeca
proventriculus
pylorus
ileum
rectum
ventriculus
anus
Foregut
Proventriculus -
intima
-grasshopper
Peritrophic membrane
Secretion
Delamination
••••••••••
••••
••• •
• • •• •••••
••
Peritrophic membrane
Membrane secreting cells
Invagination of stomatodeum
Secretion vesicles
Peritrophic membrane
Peritrophic membrane
Peritrophic membrane
Bacterium
Food
Peritrophic membrane
Peritrophic membrane
Peritrophic membrane
Enclosing fecal pellet
Peritrophic membrane
pharynx
esophagus
crop
Malpighian tubulessalivary glands
cibarium
salivariumgastric caeca
proventriculus
pylorus
ileum
rectum
ventriculus
anus
Midgut Enzymes -
Insect Diet Protease Lipase Amylase Invertase Maltase
Cockroach omnivorous √ √ √ √ √
Carausius phytophagous √ √ √ √ √
Lepidoptera larvae
phytophagous √ √ √ √ √
adults nectar √
adults Non-feeding
Lucilia meat √ √
Glossina blood √
Termites
Absorption of digested material
Absorption of digested material
Movement of H20
Movement of water, inorganic ions, sugars & amino acids
caecum
Malpighian tubule
Absorption of digested material
Cicadas
Fat Body
Cross section of mosquito abdomen (FB = fat body)
Fat Body
Functions of fat body
- metabolism of carbohydrates, lipids and nitrogenous compounds
- storage of glycogen, fat and protein
- regulation of blood sugar
-synthesis of major hemolymph (blood) proteins(haemoglobins, vitellogenins, storage proteins)
Fat Body
Functions of fat body – changes with needs – e.g. calliphorin
10
5
0
Am
ount
of
call
ipho
rin
in h
emog
lobi
n
~7
~3
~.03
Fat Body – cell types
Trophocytes-carry out most of functions of fat body
Urocytes- storage of urates/uric acid