Lecture 16: Insect Endocrinology

Question 1

In all organisms, controls activities that require long duration:

Answer 1

• digestion and metabolism
• osmoregulation
• growth + development
• reproduction

Question 2

endocrine:

Answer 2

• glands
• blood or lymph
• circulate round whole body

Question 3

exocrine glands:

Answer 3

• ducts

- epithelial surface

Question 4

Neuroendocrine system :

Answer 4

Nervous system + endocrine system.

– in insects, endocrine system - regulates physiological & biochemical processes

Question 5

nervous system:

Answer 5

• rapid & short-term

- neurons-neurosecretory cells - chemical

Question 6

Endocrine system:

Answer 6

• co-ordinates long term events

- hormones

Question 7

Holometabolous :

Answer 7

complete metamorphosis

Question 8

Hemimetabolous:

Answer 8

incomplete metamorphosis

Question 9

metamorphosis:

Answer 9

the process of transformation from an immature form to an adult

Question 10

key components of insect endocrine system:

Answer 10

• Neurosecretory cells
• Corpora cardiac
• Corpora allata
• Prothoracic glands

Question 11

Neurosecretory cells:

Answer 11

• inputs from CNS neurons to dendrites

- dendrites –> Soma –> axon –> terminal –> to then capillary

Question 12

Corpora cardiaca:

Answer 12

lie posterior to the brain and function in the storage and secretion of brain hormone.

Question 13

Corpora allata

Answer 13

an endocrine gland which generates juvenile hormone; as such, it plays a crucial role in metamorphosis.

Question 14

Prothoracic glands

Answer 14

either of a pair of endocrine glands located in the prothorax of certain insects that regulate molting

Question 15

Major insect horn types:

Answer 15

• neurohormones
• Ecdysteroids
• juvenile hormone
• Prothoracicotropic hormone (PTTH)

Question 16

neurohormones:

Answer 16

• Most diverse class
• Regulate various developmental and metabolic processes
• Modes of action: Along nerve axons, trough haemolymph
(carrier proteins
• Indirect: through effects on other glands

Question 17

ecdysteroids:

Answer 17

• Primarily ß-ecdysone.

* Moult-promoting but many other functions

Question 18

Juvenile hormone:

Answer 18

• many functions
• Secreted by corpora allata
• Regulates developmental transition
• Promotes expression of larval characteristics
• Prevents moulting by inhibiting JH
• Regulates egg production & mating behaviour
• Social insects – caste development

Question 19

Prothoracicotropic hormone (PTTH)

Answer 19

• “brain hormone”: 1st insect hormone to be described by Kopeć & Wigglesworth
• Secreted by neurohemal organ (neurosecretary cells) in brain
• Acts on prothoracic glands which release ecdysone.

Question 20

Ecdysis (moulting) is controlled by

Answer 20

Ecydysome

Question 21

Hormone Function Details: Metamorphosis

Answer 21

• JH levels initially high
• Levels begin to fall as larva
grows
• When JH falls below certain level, and ecdysone is high, pupation occurs
• Continues to decline during pupation
• At minimum JH production, adult forms

Question 22

Hormone Function Details: Reproduction

Answer 22

• JH levels rise in the adult
– Stimulates reproduction
– Vitellogenesis – production of yolk proteins transferred into eggs
– Courtship behaviour
– Pheromone synthesis
– Male accessory gland development
– Sexual receptivity
– Oviposition – egg laying

Question 23

exocrine glands have 2 components:

Answer 23

• Glandular

- duct

Question 24

Chemoreception:

Answer 24

- Gases, liquids, solids…
- Smell(remote); taste(contact)
- Olfactory receptor neurons in sensill

Question 25

Semiochemicals

Answer 25

• Semio (greek; semeon = sign/signal)
• small organic compounds that transmit chemical messages
• used by insects for intra- and inter- species communication
• receptors are usually located in sensilla hairs on the
antennae or on legs