Air Breathing: Why?

Question 1

How many species air breathe?

Answer 1

• 374/30 000

Question 2

What is a facultative air breather?

Answer 2

• breathes both water an air

Question 3

What are obligate air breathers?

Answer 3

• drown if denied access to air

Question 4

What are some examples of obligate air breathers?

Answer 4

• african lungfish
• mudskipper

Question 5

Why breathe air? What is the difference of O2 in air vs water?

Answer 5

• lots of O2 avail (210mL vs 6ml/L)

Question 6

What is aquatic hypoxia?

Answer 6

• low O2 in water

Question 7

Where did air breathing evolve?

Answer 7

in water

Question 8

What is one way to breathe air? What is the main disadvantage?

Answer 8

• at water-air interface
• predation: birds above, fish below

Question 9

Why is the water:air interface a good place to obtain O2?

Answer 9

• warmer water, [O2] and solubility decrease = increase in air breathing frequency

Question 10

What are 4 reasons a fish may breathe air?

Answer 10

• can take advantage of O2 at interface
• desiccation of habitat
• receding waters
• overland migrations

Question 11

What is an example of habitat desiccation? What fish breathe air because of this?

Answer 11

• water evaporates
• lungfish, walking catfish

Question 12

What is an example of receding water? What fish are adapted to this?

Answer 12

• tides
• intertidal fish (killfish)

Question 13

Why mau overland migrations take place? Give an example for each. (3)

Answer 13

• poor water quality (walking catfish)
• spawning (lamprey overcome obstacles)
• foraging/habitat selection (mudskippers)

Question 14

What are the main problems associated with air breathing?

Answer 14

• gills are designed for water breathing and physically supported by water
  –> collapse in air (decrease SA)
  –> air flow decreases + desiccation (dry out)

Question 15

What are the 4 main solutions to air breathing issues?

Answer 15

• thicker/widely space lamellae
• retain gills in moist microenvironment
• limit migrations to moist periods
• use other aerial respiration

Question 16

How do fish retain gills in moist microenvironment?

Answer 16

• burrow
• modified operclar chambers (closed off) (mudskipper)
• greater internalization of gill (american eel)

Question 17

Why do fish limit migrations to moist periods? Give an example.

Answer 17

• higher humidity
• american eel migrate through moist grass

Question 18

What is a major alternative to gill breathing?

Answer 18

• Accessory air breathing organs

Question 19

What are 4 accessory air breathing organs?

Answer 19

• cutaneous respiration (skin, buccal cavity)
• swallow air (gut)
• Specialized swim bladder
• lungs (vascularization)

Question 20

Gills are ____ in air breathers.

Answer 20

• generally reduced

Question 21

Why are gills generally reduced in air breathers?

Answer 21

• with them, O2 is taken from air, through heart and lost from gills.
• they want O2 to tissues that need it without it getting lost to gill

Question 22

What kind of breathers are amphibious air breathers?

Answer 22

• both air and water

Question 23

What kind of breathers are aquatic air breathers?

Answer 23

• air IN water

Question 24

What kind of breathers are non-air breathers?

Answer 24

• just water

Question 25

Blood PO2 is _____ than water PO2. Why?

Answer 25

• higher because O2 is lost to environment