INSECT DIGESTIVE SYSTEMS

Insect Digestive System Developmentally Foregut (stomatodeum) - ectodermal 2. Hindgut (proctodeum) - ectodermal 3. Midgut (mesenteron) - endodermal cuticle

FOREGUTMIDGUTHINDGUT

pharynx esophagus crop Malpighian tubules salivary glands cibarium salivarium gastric 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

Two types 1.Acinous (alveolar) – multicellular with sac-like units -directly innervated from CNS Subesophageal ganglion Produces dopamine for fluid secretion Stomatogastric NS Produces 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, J. Med. Ent 45:409 Lutzomyia longipalpis

Insect Saliva – Composition - changes Prates et al, J. Med. Ent 45:409 Lutzomyia longipalpis

Salivary Glands Aphid Blood feeders Silk cocoons Plant galls

Salivary glands are involved in disease transmission

Foregut Cicada (Homoptera)

pharynx esophagus crop Malpighian tubules salivary glands cibarium salivarium gastric 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

Bacterium Food

Peritrophic membrane

Enclosing fecal pellet Peritrophic membrane

pharynx esophagus crop Malpighian tubules salivary glands cibarium salivarium gastric caeca proventriculus pylorus ileum rectum ventriculus anus

Midgut Enzymes - InsectDietProteaseLipaseAmylaseInvertaseMaltase Cockroachomnivorous √√√√√ Carausiusphytophagous √√√√√ Lepidoptera larvae phytophagous √√√√√ adultsnectar √ adultsNon-feeding Luciliameat √√ Glossinablood √

Termites

Absorption of digested material

Movement of H 2 0 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 Amount of calliphorin in hemoglobin ~7 ~3 ~.03

Fat Body – cell types Trophocytes -carry out most of functions of fat body Urocytes - storage of urates/uric acid