Week 9 (Insect) physiology

Question 1

pupation origin

Answer 1

from a ligation experiment (strangle to separate the larvae to 2 halves)
- Only the anterior pupates

Question 2

When do both anterior and posterior pupate in ligation experiment?

Answer 2

1. injection of molting hormone into posterior
2. if the hormone is already released into haemolymph

Question 3

brain removal effect on pupation

Answer 3

has endocrine effects.
Brain removal before release of hormone leads to no pupation

Question 4

kissing bug - moving from a nymph stage to the next

Answer 4

needs to feed on blood

Question 5

decapitation

Answer 5

head removal from body

Question 6

decapitation effect on moulting

Answer 6

Decapitation early after a meal, the kissing bug will not undergo moulting.
- A critical period.

Question 7

how to find source of hormone

Answer 7

for example, after removal of brain - implantation of specific body parts to

Question 8

brain hormone

Answer 8

prothoracicotropic hormone (PTTH)

Question 9

is PTTH released into the blood (insect)

Answer 9

parabiosis experiment: hormone is indeed effective on both insects.
Allow free flow of haemolymph between two decapitated insects.
- one decapitated before critical period
- one decapitated after critical period

Question 10

parabiosis proves…

Answer 10

blood-borne hormone is responsible for metamorphosis induction.

Question 11

how does PTTH control metamorphosis

Answer 11

using the larvae of the silkworm - if the brain is taken out
- the larvae doesn’t mature to the adult form
- reversible from implantation

Question 12

Does hormone from implanted brain directly act on tissues?

Answer 12

development:
- anterior half - YES
- posterior half - NO
- posterior half + thorax - YES

PROTHORACIC GLAND = development

Question 13

brain and prothoracic gland and further hormone action

Answer 13

brain releases PTTH and acts on prothoracic gland
- the gland releases another hormone.

Question 14

what hormone does the prothoracic gland produce?

Answer 14

Ecdysone - steroid hormone
It acts directly on tissues and induce moulting.

Question 15

how does ecdysone act molecularly?

Answer 15

As a steroid hormone, it diffuses easily into cells
- In its presence, the ultraspiricle will combine with the ecdysone receptor
- when ecdysone binds to the receptor complex
- translocate to nucleus and alter gene expression.

Question 16

ecdysone effect on chromosome

Answer 16

decondense bands/regions of chromosome, allowing gene transcription

Question 17

pulses of ecdysone will lead to transition to different stages of development

Answer 17

inhibitory hormone

Question 18

what’s the inhibitory hormone that stops the transition from nymph to adult?

Answer 18

the juvenile hormone
- from corpus allatum

Question 19

juvenile hormone effects

Answer 19

it will alter ecdysone-stimulated moults to a new larval instar
- in the last larval instar – JH will drop below a critical threshold due to inhibition
- in the absence of JH, the larvae will turn to an adult

Question 20

small size of insect implication

Answer 20

Large surface to volume ratio
LARGE water FLUCTUATION - dehydrate/rehydrate

Question 21

insect renal tubule

Answer 21

they don’t have pressure difference to do filtration.
act on haemolymph
They produce urine by secretion

Question 22

type of cells in renal tubule (insect)

Answer 22

principal and stellate cells

Question 23

generation of primary urine (principal cell)

Answer 23

1. through an ATPase, H+ is pumped to the lumen
2. with H+ gradient, K+ is brought out to the lumen
3. K+ is also transported into the cell from the haemolymph

Question 24

generation of primary urine (stellate cell)

Answer 24

1. due to favourable electrochemical gradient, Cl- is also transported from haemolymph to lumen
2. water follow by osmosis - aquaporin in stellate cells and between cells.

Question 25

What is the Ramsay Assay?

Answer 25

It measures the secretory function of the insect renal tubule
- extract renal tubule and put into saline
- open a hole on the other end and investigate the lumen of the tubule.

Question 26

kinin function in insect renal tubule

Answer 26

Enhance secretion:
Works in stellate cells, stimulate absorption of Cl-

Question 27

cAMP function in insect renal tubule

Answer 27

Enhance section:
Works in principal cells, stimulate H+ ATPase, pump out H+ to create gradient for K+ to be pumped out.

Question 28

finding the source of diuretic factor in insects

Answer 28

adding body parts to the ramsay assay apparatus: mesothorax ganglia releases diuretic hormone.
- the CNS increases secretion
- mesothorax increases secretion

Question 29

which diuretic hormones act on insect principal cells?

Answer 29

diuretic hormone
serotonin
CAPs

Question 30

what diuretic hormone act on stellate cells?

Answer 30

kinins

Question 31

What sort of physical signal leads to insect diuresis?

Answer 31

A stretch receptor in the abdomen:
- releases sertonin and CRF (diuretic hormone)
- These hormones act on principal cells.

Question 32

how does the insect recover water and electrolytes after secretion?

Answer 32

In the rectum:
- The chloride transport stimulating hormone (CTSH) will stimulate chloride transport out of the lumen.
- potassium will passively follow through electrical coupling - k+ channel
- water will diffuse out along with ion reabsorption

Question 33

insect water conservation in extreme environments

Answer 33

beetle: buried kidney complex
tubules very close to rectum
- conserve water passed from ‘wet faeces’ from hindgut.
- taking water from rectum

Question 34

water vapour absorption - insect

Answer 34

The beetle: countercurrent exchange system
Has a pump that pumps in K+ and Cl- into the renal tubule:
- high electrolyte concentration close to the rectum
- water content is high further away from rectum
- always a difference between water content and electrolyte concentration.
- water will be absorbed