Air Breathing: Why? Flashcards
How many species air breathe?
- 374/30 000
What is a facultative air breather?
- breathes both water an air
What are obligate air breathers?
- drown if denied access to air
What are some examples of obligate air breathers?
- african lungfish
- mudskipper
Why breathe air? What is the difference of O2 in air vs water?
- lots of O2 avail (210mL vs 6ml/L)
What is aquatic hypoxia?
- low O2 in water
Where did air breathing evolve?
in water
What is one way to breathe air? What is the main disadvantage?
- at water-air interface
- predation: birds above, fish below
Why is the water:air interface a good place to obtain O2?
- warmer water, [O2] and solubility decrease = increase in air breathing frequency
What are 4 reasons a fish may breathe air?
- can take advantage of O2 at interface
- desiccation of habitat
- receding waters
- overland migrations
What is an example of habitat desiccation? What fish breathe air because of this?
- water evaporates
- lungfish, walking catfish
What is an example of receding water? What fish are adapted to this?
- tides
- intertidal fish (killfish)
Why mau overland migrations take place? Give an example for each. (3)
- poor water quality (walking catfish)
- spawning (lamprey overcome obstacles)
- foraging/habitat selection (mudskippers)
What are the main problems associated with air breathing?
- gills are designed for water breathing and physically supported by water
–> collapse in air (decrease SA)
–> air flow decreases + desiccation (dry out)
What are the 4 main solutions to air breathing issues?
- thicker/widely space lamellae
- retain gills in moist microenvironment
- limit migrations to moist periods
- use other aerial respiration
How do fish retain gills in moist microenvironment?
- burrow
- modified operclar chambers (closed off) (mudskipper)
- greater internalization of gill (american eel)
Why do fish limit migrations to moist periods? Give an example.
- higher humidity
- american eel migrate through moist grass
What is a major alternative to gill breathing?
- Accessory air breathing organs
What are 4 accessory air breathing organs?
- cutaneous respiration (skin, buccal cavity)
- swallow air (gut)
- Specialized swim bladder
- lungs (vascularization)
Gills are ____ in air breathers.
- generally reduced
Why are gills generally reduced in air breathers?
- 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
What kind of breathers are amphibious air breathers?
- both air and water
What kind of breathers are aquatic air breathers?
- air IN water
What kind of breathers are non-air breathers?
- just water
Blood PO2 is _____ than water PO2. Why?
- higher because O2 is lost to environment
