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Flashcards in Excretion and Water Balance Deck (91)
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1

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

2

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)

3

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

4

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

5

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

6

why would insects feed on toxic plants?

- nutrution
- defense
- synthesis

7

What happens during dehydration for an insect?

-low blood pressure and a dramatic drop in blood volume during dehydration

8

Why are the effects not especially detrimental?

Hemolymph is not used for gas exchange

9

What is a consequence of of dehydration?

Formation of primary urine in insects cannot occur by pressure driven filtration

10

What do most insects actively secrete?

K+ (with Cl- as anion) forming KCl rich urine

11

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

12

What is the main excretory organ in insects?

Malpighian tubules

13

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

14

Which insects lack malpighian tubules?

Aphids and collembola

15

What are Malpighian tubules?

A slowly operating system for secretion of primary urine

16

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

17

What is the main excretory product?

Uric acid

18

What is the main function of the excretory system?

Removed nitrogenous (metabolic) wastes

19

Which takes longer to completely filter their blood, humans or insects?

Insects

20

What do mapighian tubules secrete?

sugars, amino acids, water, KCl, toxins and nitrogenous wastes

21

Where is primary urine secreted?

from the Malpighian tubules to the hind gut

22

Where is a major source of water balance in the insect (where most water is reabsorbed)?

Rectum

23

What is reabsorbed in the hindgut?

sugars, amino acids and ions (to maintain osmolity of the hemolymph)

24

What does reabsorption of water in the rectum facilitate?

K+ secretion in the malpighian tubules

25

Where are the distal ends of the malpighian tubules fused?

the rectal wall

26

What does diuretic hormone do?

-stimulates diuresis
- Promotes water loss

27

What does antidiuretic hormone do?

- Prevents water loss by promoting fluid reabsorption in the hindgut

28

What is diuretic hormone stimulated by?

Distention of the gut

29

What is anti diuretic hormone stimulated by?

Dehydration

30

What is Rhodnius?

Hemolymph from bloodfed bug is injected into an unfed bug which stimulates diuresis