Flashcards in Excretion and Water Balance Deck (91)
Insects, like most animals, must Maintain and eliminate what?
Maintain a reasonably constant blood composition and total water content for cell viability and must eliminate toxic wastes
Where can Euryhaline mosquito larvae survive and how?
In everything from fresh water to 300% sea water and alkaline salt lakes
- Drink their own body weight every few hours to harvest dilute food from pond sediments (Filter feeders)
Where do mealworms live, what do they eat and what kind of excrement do they produce?
- Lives in dry environment, eats dry food and produces dry excrement
Desert locusts, what do they eat and what kind of excrement do they produce?
- consume own weight in succulent plants and produce moist excreta unless they are starved in which case they produce dry excreta
What is the general nature of the excretory process? why do they take place?
1. Eliminate most blood solutes non-selectively; takes place in the malpighian tubules
2. Selectively reabsorb useful solutes; takes place in the hindgut (mostly)
3. Actively secrete certain toxins (malpighian tubules
why would insects feed on toxic plants?
What happens during dehydration for an insect?
-low blood pressure and a dramatic drop in blood volume during dehydration
Why are the effects not especially detrimental?
Hemolymph is not used for gas exchange
What is a consequence of of dehydration?
Formation of primary urine in insects cannot occur by pressure driven filtration
What do most insects actively secrete?
K+ (with Cl- as anion) forming KCl rich urine
What does an insects KCl rich urine cause?
A large concentration gradient between the hemolymph and malpighian tubule lumen for diffusion of all other blood solutes
What is the main excretory organ in insects?
What is the structure of malpighian tubules?
Blind-ended tubules composed of a single layer of epithelial cells (3 cells when seen in a cross-section.
- can be differentiated histologically along their length with up to 4 distinct sections
Which insects lack malpighian tubules?
Aphids and collembola
What are Malpighian tubules?
A slowly operating system for secretion of primary urine
Why are all the nutrients excreted and then reabsorbed as needed?
It is energetically more favorable cause it is easier to reabsorb needed molecules passively than to actively excrete all unneeded ones
What is the main excretory product?
What is the main function of the excretory system?
Removed nitrogenous (metabolic) wastes
Which takes longer to completely filter their blood, humans or insects?
What do mapighian tubules secrete?
sugars, amino acids, water, KCl, toxins and nitrogenous wastes
Where is primary urine secreted?
from the Malpighian tubules to the hind gut
Where is a major source of water balance in the insect (where most water is reabsorbed)?
What is reabsorbed in the hindgut?
sugars, amino acids and ions (to maintain osmolity of the hemolymph)
What does reabsorption of water in the rectum facilitate?
K+ secretion in the malpighian tubules
Where are the distal ends of the malpighian tubules fused?
the rectal wall
What does diuretic hormone do?
- Promotes water loss
What does antidiuretic hormone do?
- Prevents water loss by promoting fluid reabsorption in the hindgut
What is diuretic hormone stimulated by?
Distention of the gut
What is anti diuretic hormone stimulated by?