BIOD33H3 Lecture Notes - Lecture 2: Ectotherm, Amazon River, Branchial Arch
24 Oct 2018
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BIOD33 Lec 2
- Fish for the most part are ectothermic, they don’t have physiological means to generate
heat
- They can use behavioral means to warm themselves, by moving to areas
- They are poikilotherms bc they take on the temp of their environment
- Large active fish (sharks, tuna) have heating generating systems in the core of their body,
which generates heat and can trap heat
- They can maintain their core muscles, 20-25 degrees higher than the temp they are in,
allows muscle to be more active, more range for biochemical reactions
- some do futile cycling of calcium, where calcium leaks into cell, pumped out and this
produces heat, and the cycle repeats
- So not all fish are cold as death
- Salt water fish are always drinking
- Fresh water fish do not drink
- Some fish don’t have scales
- Gills are fine delicate tissues
- In order to keep spatial distance, they need water around them
- If they were to go in air, the gills will collapse onto each other and then cant be ventilated
or exchange gasses
- Have sets of gills on either side of fish
- Some fish that have mofdified gills and can breathe air
- These are shorter, stubbier gills, which are less prone to cllapsing in air
- Top of the water, in contact with air is well oxygenated
- Lower in the water, the greater the diffusion, and less oxygen present as you go deeper in
water
- The fish move to the surface of the water, funnel the surface water into their mouths and
over their gills, so breathing the well ventilated water
- Can take advantage of high o2 in water at the top
- Disadvantage is that by coming up to the surface they expose themselves to predators,
cant hide from predators, so it’s a trade off between O2 and prey
- Tambagui use their lips to form a funnel like structure, can have water funnel in their
mouths and across their gills
- Obligatory breathing in sharks
- most fish breathe by pumping water through the mouth and across their gills
- Some fish use their rapid rate of swimming, with mouth open, to ram the water across the
gills, and that’s sufficient water flow to meet their oxygen and metabolic demands
- At lower speed, they use muscles to breathe, as they speed, they use ram ventilation
- Only 2 dozen species of sharks that need ram ventilation (obligatory)
- Most can switch between the types of ventilation
- Tuna can use it, but they don’t have to
- Some fish will breathe air
- Some fish must breathe air (lung fish)
- Most obligatory air breathing is done with true lungs, swim bladders (air bladder),
modified gills
- Most are using lungs or swim bladders
- Also have facultative air breathing, brething of air when not enough o2 in water
- Air breathing evolved bc eventually o2 levels in water depleted so animals developed
structures to breathe air, to exploit a constant, steady supply of oxygen that’s present in
the air
- The environments where air breathing evolved are the tropical and neo-tropical areas
which leads to cycles of water levels with low and high oxygen either on a seasonal basis
or circadian rhythm (day/night)
- During the rainy season it floods the forest and surrounding area
- Water levels can rise upto 7 meters in the amazon river
- When the water recedes, it leads to conditions ideal for air breathing structures
Document Summary
Fish for the most part are ectothermic, they don"t have physiological means to generate heat. They can use behavioral means to warm themselves, by moving to areas. They are poikilotherms bc they take on the temp of their environment. Large active fish (sharks, tuna) have heating generating systems in the core of their body, which generates heat and can trap heat. So not all fish are cold as death. In order to keep spatial distance, they need water around them. If they were to go in air, the gills will collapse onto each other and then cant be ventilated or exchange gasses. Have sets of gills on either side of fish. Some fish that have mofdified gills and can breathe air. These are shorter, stubbier gills, which are less prone to cllapsing in air. Top of the water, in contact with air is well oxygenated.
