Integument, Molting and Endocrine Control Flashcards

1
Q

What are the major constituents of an insect cuticle? (2)

A
  1. Chitin

2. Proteins

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2
Q

What is lamellae?

A

A polymer chain of N-acetylglucosamine that are bound by proteins to form sheets

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3
Q

How is the cuticle made unstretchable?

A

Lamellae are laid down at different angles every half hour

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4
Q

How much of the chitin in the cuticle is reabsorbed during molting?

A

about 85%

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5
Q

Where are proteins found in the insects cuticle?

A

Cross-linked to lamellae

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6
Q

What are the layers of the cuticle from the outermost layer to innermost layer? (4)

A
(Outermost)
- Epicuticle
- Exocuticle
- Endocuticle
- Epidermis
(Innermost)
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7
Q

What is the function of the Epicuticle?

A

provides a waterproof layer for the insect and prevent water loss

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8
Q

What is the function of the Exocuticle?

A

Forms a protective shell (hardened by sclerotization

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9
Q

What is the function of the Endocuticle?

A

To be reabsorbed during molting. Not sclerotized

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10
Q

What is the function of the Epidermis?

A

To produce all the layers of the Integument. Only actual living part of the integument

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11
Q

How is wax formed on the Epicuticle and why?

A

A gland in the epidermis extends all the way up to the top most layer to create the wax covering in order to prevent water loss and waterproof the insect

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12
Q

What are the three stages of molting? (in order)

A
  1. Apolysis
  2. Ecdysis
  3. Sclerotization
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13
Q

What is Apolysis?

A

The separation of the epidermis from the cuticle of the previous stage

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14
Q

What is Ecdysis?

A

The casting off or escape from the residual cuticle of the previous stage. There is a fully formed insect inside the old cuticle prior to this stage

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15
Q

What is Sclerotization (in regard to molting)?

A

A chemical process that hardens the outer section of cuticle (exocuticle) after ecdysis by cross-linking cuticular proteins with oxidized phenols.
occurs from the outside in.

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16
Q

What is a pharate?

A

The fully formed insect inside the old cuticle prior to ecdysis

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17
Q

What is an exuvium?

A

The cast off cuticle after ecdysis

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18
Q

What is a teneral adult?

A

An insect that has not finished sclerotizing its integument after molting

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19
Q

What are the 6 stages the cuticle goes through during molting?

A
  1. Apolysis
  2. Production of cuticulin
  3. Digestion of endocuticle
  4. Resorption of molting fluid
  5. Cuticle immediately after Ecdysis
  6. Mature cuticle
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20
Q

What hormone controls sclerotization?

A

bursicon

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21
Q

What are the two types of sclerotization? Which is light and which is dark colored?

A
  1. Quinone Tanning - Dark colored

2. Beta-Sclerotization - Light colored

22
Q

What are some unsclerotized parts of an insect?

A

the intersegmental membranes, the joints and appendages

23
Q

What is sclerotized in a holometabolous larvae?

A

The head capsule, mandibles and true legs

24
Q

What does ecdysis depend on in many species?

A

Blood pressure and/or air pressure

25
Q

How is ecdysis performed in many insects?

A

Insect contracts abdomen for a prolonged period of time which forces blood into the head and thorax. can be assisted by swallowing air

26
Q

What is ecdysis often aided by? How?

A

Aided by gravity
- insect hangs upside down, secured by claws of the hind tarsi. Rupturing of the ecdysial cleavage line on the head capsule allows the insect to slide out of the exuvium

27
Q

How does the muscid fly perform ecdysis?

A

They have a specialized structure on the head, the ptilinum, an inflatable bladder that breaks open the puparium and allowing the adult fly to emerge

28
Q

What do insects often have to do after ecdysis? why?

A
  • Swallow air or contract specific muscles to facilitate expansion of the new cuticle prior to sclerotization.
  • Pump blood to wings to make sure they are fully expanded
29
Q

In some species, what must be done throughout the sclerotization process?

A

Muscles of the abdominal wall must remain contracted throughout

30
Q

Why are insects especially vulnerable to predators during molting?

A

They need to remain motionless during sclerotization and have a weak state of cuticle prior to and during the process

31
Q

What are 5 hormones involved in the control of molting?

A
  1. Juvenile hormone
  2. Ecdysone
  3. Prothoracicotropic hormone (PTTH)
  4. Eclosion hormone
  5. Bursicon
32
Q

What role does the juvenile hormone play in molting?

A

determines the course of development

33
Q

What role does Ecdysone play in molting?

A

Stimulates the molting process (Ecdysis and Apolysis)

34
Q

What role does the Prothoracicotropic hormone (PTTH) play in molting?

A

Stimulates the release of ecdysone (stimulates prothoracic gland to synthesize and secrete ecdysone)

35
Q

What role does the Eclosion hormone play in molting?

A

triggers molting behaviours including stereotyped sequence of behaviours involved in adult emergence from the pupa
- also stimulates release of bursicon

36
Q

What role does Bursicon play in molting?

A

Stimulates sclerotization of cuticle

  • increases permeability of epidermal cells to dopamine
  • stimulates conversion of tyrosine to dopa
37
Q

Describe the endocrine control of molting and development (in order and including hormone names for each step)

A
  1. PTTH stimulates Ecdysone synthesis and release
  2. Ecdysone tiggers molting
  3. JH titre determines the outcome of the molt
38
Q

Where is the juvenile hormone synthesized?

A

In the corpora allata glands

39
Q

What does the juvenile hormone act on?

A

Acts directly on the epidermis and internal tissues

40
Q

When does juvenile hormone occur and in what levels throughout the insects life?

A
  • Occurs throughout larval stages in gradually decreasing levels.
  • Disappears during final instar except for a brief peak just prior to pupation.
  • Reapears in adult stage to regulate reproduction
41
Q

What happens to Juvenile hormone when it is made?

A

It is not stored, it is released as synthesized.

42
Q

What are titres determined by with regard to juvenile hormone?

A

rate of degradation by specific JH esterases produced in the fat body

43
Q

What is Ecdysone synthesized from?

A

Cholesterol or plant sterols obtained from the diet

44
Q

What is ecdysone synthesized by?

A

The prothoracic gland

45
Q

What is a substitute for ecdysone and what insects use it?

A

Makisterone-A

- used by some hemipterans and the honey bee

46
Q

What type of hormone is the prothoracicotropic hormone?

A

A polypeptide

47
Q

What is the prothoracicotropic hormone produced by?

A

Specific groups of medial neurosecretory cells in the brain

48
Q

How is the prothoracicotropic hormone transported and what happens to it after it is synthesized?

A

Transported by nerve axons to the corpora cardiaca glands where it is stored

49
Q

How is the eclosion hormone released?

A

Released by a circadian clock

50
Q

Where is the eclosion hormone produced?

A

In the brain and abdominal ganglia

51
Q

Where is the Bursicon hormone produced?

A

in the perivisceral organ

52
Q

How do plants mimic Juvenile hormone?

A

Produce a number of secondary compounds that have JH-like bioactivity in insects
- also produce anti-JH compounds