L5 - Feeding and Osmoregualtion Flashcards
What are the 4 sections of the foregut?
Pharynx –> oesophagus –> crop –> proventriculus
What organ consists the midgut?
The gastric caecae
What are each lined with?
a) foregut
b) midgut
c) hindgut
a) cuticle
b) thin peritrophic membrane for protection
d) cuticle
What are the guts like of very short lived insects?
Tube like
What hormones cant insects synthesise which they must obtain from their diet or micro-organisms?
Sterols - used for moulting hormone
Carotenoids - used in visual pigments
What are the 2 types of salivary gland insects can have?
labial or mandibular
What is the function of the proventriculus
a grinding organ in some insects, can control the rate of food into the midgut
What section of the gut is the main site for absorption?
Midgut
In blood sucking insects, where is a lot of blood stored if they take a large meal at once?
a specialised portion of the midgut
What are the sections of the hindgut in order?
malpighian tubules –> ilium –> colon –> rectum –> anus
What are and what is the function of malpighian tubules?
Thin hair-like tubules found at midgut-hindgut barrier sphincter
Function is excretion
Describe the general structure of the hindgut
Can be a straight tube, or modified into a fermentation chamber storing and harbouring micro-organisms that help in cellulose digestion
Where are rectal pads found, how many of them are there, and what is their function?
6 rectal pads are embedded in the wall of the rectum.
These absorb water - in dry conditions they can absorb up to 90% of the water from the excretion
What is the structure of the walls of the hind gut like?
Epithelium rests on the basal lamina. The walls contain both longitudinal and circular muscle for peristalsis
What are the 3 basic types of insect mouthparts?
1) mandibulate - chewing and biting
2) Haustellate - lapping and sucking
3) Piercing
What is the fat body?
Loose sheets/ribbons/lobes of cells lying in the body cavity (Haemocoel). These cells are in communication via gap junctions
What are the functions of the fat body?
1) An energy store:
e. g.: Octopamine released from the brain mobilises fat to be metabolised during flight
2) Regulates blood sugar
- insects have insulin like peptide (Dilps) released from
- dietary amino acids activate TORC1 in fat cells - induces the production of Dilps
3) Synthesises major haemolymph proteins
e. g.: in females its used for a site of storage of vitellogenin
What 3 ways can insects get rid of waste nitrogen?
1) Ammonia - is very toxic so must be excreted in a dilute form, or rapidly colletized (cocraches)
2) Urea - less toxic and more soluable, still requires water for elimination
3) Uric acid - not toxic, can be excreted dry and stored by most. It also has a high N:H ratio therefore less water used for excretion
Describe the ‘general condition’ of the hindgut
1) Malpighian tubules absorb water, solutes and urate (uric acid) from the haemolymph in the body cavity
2) The rectum then reabsorbs water and solutes from the gut, leaving urate and precipitate behind to be excreted. Ions are then actively transported back (mitochondria positioned for this) water follows
Describe the state of the hind gut in Liquid feeders
1) Distal MTs absorb water, solutes and urate/uric acid from the Haemocoel
2) Proximal MTs reabsorb water and solutes
3) Tubules are then flushed out and uric acid excreted because of the next blood meal
What effects on the insect does a blood meal have?
A blood meal can be 10times the insects unfed weight, which can reduce flight speed from 15 to 3-4mph
In the tsetse fly, 40% of the meal is shed in 30mins. Mostly nutrient poor plasma, strong active transport mechanism in the epithelium of distal MTs
Diuretic hormones released in gut distension enables haematophagous (and probably also phytophagous) insects to deal with sudden large dietary loads
- After a blood meal, DH can increase water transport by x1000 in rohdnius
- after a Blood meal high ion concentration therefore
Describe what happens in an insects gut in water stress?
During dry periods, water can be absorbed from the air by the rectum:
- distal regions of the MTs are wrapped around them
- ‘cryptonephridial system’
Ions are transported in high concentrations (mainly KCl) in the 6MTs. This draws liquid from the perirectal space and rectal lumen. This is then transported to free tubule and reabsorbed haemolymph or recycled in the rectum
