W9: Invertebrate Physiology (Physiology Overview 2) [Dr. Blair]

Question 1

If there are no blood vessels or haemoglobin, how do insects get O2?

Answer 1

Insects take in O2 through the spiracles which lead to the tracheal system (trachea & tracheoles), which then go directly to the tissues and cells.

Question 2

Spiracle?

Answer 2

= an opening to the tracheal system of insects found along the abdomen of insects.

Question 3

No lungs? Without actual lungs, wouldn’t body size influence insect respiration?

Answer 3

Yes.

Question 4

What’s the world’s smallest insect?

Answer 4

Fairy flies/wasps.

Question 5

Fairy flies/wasps attributes? (2)

Answer 5

• Parasitic wasps.
• ~0.1mm in size.

Question 6

What’s the world’s largest insect?

Answer 6

Depends on if you mean in terms of size or weight.

Question 7

2 views to consider when indicating the world’s largest insect? (2)

Answer 7

• Size.
• Weight.

Question 8

World’s largest insect in terms of size?

Answer 8

Elephant beetle.

Question 9

World’s largest insect in terms of weight?

Answer 9

Gaint weta/Wetapunga (New Zealand cricket).

Question 10

Insect respiration in smaller insects attributes? (3)

Answer 10

• Use passive diffusion.
• Limits body size as increased size lowers efficiency of gas exchange.
• Small body size = Passive diffusion/”energy free”

Question 11

Insect respiration in larger insects attributes? (5)

Answer 11

• Passive diffusion is problematic.
• Highly efficient.
• Larger tracheae.
• Large air sacs.
• Active ventilation.

Question 12

How do larger insects overcome the problematic nature of passive diffusion? (30

Answer 12

• Larger tracheae (increases volume of air).
• Air sacs (provide air stores & increased ventilation).
• Active ventilation.

Question 13

How does active ventilation help larger insects overcome passive diffusion problem?

Answer 13

The contraction of muscles coupled with activity increases circulation.

Question 14

Efficiency of insect respiration?

Answer 14

Enables sustained flight (open spiracles: aerobic).

Question 15

What about aquatic insect respiration?/Aquatic insect respiration attributes? (2)

Answer 15

• Difficult to take O2 in without taking inhaling water as well.
• No spiracles in technical positions to prevent taking in water while breathing.

Question 16

Ways to get O2 in but not water & allow CO2 out in aquatic insects?/What about aquatic insect respiration? (4)

Answer 16

• “Physical” gills/Plastrons.
• Cutaneous respiration.
• Air bubbles.
• Tracheal gills.

Question 17

Explain “Physical” gills/Plastrons?

Answer 17

Plastrons trap a thin layer of air & allow O2 from the water to diffuse into the trapped air layer, and then into the insect’s tracheal system, while CO2 diffuses out.

Question 18

Explain Cutaneous respiration?

Answer 18

O2 from the water diffuses across the insect’s thin body surface into the haemolymph, where it is transported to the insect’s tissues. CO2 is similarly released back into the water.

Question 19

Explain Air bubbles?

Answer 19

When aquatic insects trap air bubbles from the surface & carry them underwater (bubbles act as temporary oxygen reservoirs). As the insect consumes oxygen, more oxygen diffuses into the bubble, keeping it oxygenated for a time.

Question 20

Explain Tracheal gills?

Answer 20

Oxygen diffuses from the water through the tracheal gills into the tracheal system, where it is transported directly to the tissues, while carbon dioxide diffuses out.

Question 21

Egs of aquatic insect that uses “Physical” gills? (2)

Answer 21

• Backswimmers (Notonecta).
• Some water bugs.

Question 22

Eg of aquatic insect that uses Cutaneous respiration?

Answer 22

Larvae of some stoneflies.

Question 23

Eg of aquatic insect that uses Air bubbles?

Answer 23

Water beetles.

Question 24

Eg of aquatic insect that uses Tracheal gills?

Answer 24

Mayflies.

Question 25

Feeding, digestion & excretion in insects?

Answer 25

Since insects feed on various forms of organic matter (blood, nectar, plant material, decaying matter, faeces), this influences the kinds of digestive systems they have & their digestive specialisations.

Question 26

Digestion?

Answer 26

= breakdown of “food’ into components that can be absorbed by the body.

Question 27

What food elements do insects go for in their foods? (3)

Answer 27

• Macronutrients (Carbohydrates, Proteins, Fats).
• Minerals.
• Vitamins.

Question 28

Insect digestive system plan/parts? (3)

Answer 28

• Foregut.
• Midgut.
• Hindgut.

Question 29

Foregut attributes? (3)

Answer 29

• Acquire food.
• Initial digestion occurs (softening).
• Comprises the mouth/oesophagus/crop (some).

Question 30

Midgut attributes? (3)

Answer 30

• Main region of digestion & nutrient uptake.
• Length is inversely proportional to the nitrogen level in food.
• High nitrogen diet, short midgut length.

Question 31

Hindgut attributes? (4)

Answer 31

• Final passage of digestive system.
• Non-nutritive material out.
• Waste materials enter (Malpighian tubules).
• Reabsorb water & anything useful.
• Excretory products are excreted as dry/semi-solid.
• Comprises the intestine/rectum/anus.

Question 32

What more do insects need for efficient digestion?

Answer 32

Microbial symbionts.

Question 33

Function of symbionts?

Answer 33

Synthesize vitamins & minerals.

Question 34

Symbionts?

Answer 34

= micro-organisms such as those found in blood, sap, plants & dung, as well as fungi and insects.

Question 35

What 2 parts does Insect excretion focus on? (2)

Answer 35

• Malpighian tubules.
• Hindgut.

Question 36

Malpighian tubules attributes? (2)

Answer 36

• Filter haemolymph.
• Filter waste (uric acid & water).

Question 37

Thing to note about insect excretion?

Answer 37

Aquatic insects’ waste product is urea, like mammals.

Question 38

Super summary? (3)

Answer 38

• Respiration (spiracles, trachea, tracheoles, effcient system O2, cells).
• Digestion (foregut, midgut, hindgut & microbial symbionts).
• Excretion (waste & malpighian tubules, hindgut).