Flashcards in Lecture 1 - Habitats - Special Habitats Deck (35)
What are the main problems that arise with living at depth?
1 - Pressure
2 - Light
3 - Cold
4 - Lack of food
5 - lots of empty space (hard to find mates)
Pressure increases linearly with depth at a rate of ______.
Why can fish survive such high pressures?
1 - Their flesh is the same density as water, meaning it is incompressible.
2 - Deeper living fish lose their fish bladder. i.e. do not keep gases in their tissues
How do fish get around the lack of light?
1 - Fish get smaller eyes or lose eyes altogether
Why is the loss of eyes an important feature at depth?
At depth, light is lacking, if present, and is a waste of energy and a metabolically expensive organ. Thus, reduction in a non-essential feature is important since it will save energy given that food is sparse
What are other features that fish living at depth have lost?
Pigments, useless since they cannot be seen.
What are features, related to metabolism, of fish at depth?
Fish can subsist on a given meal longer than pelagic fish.
This is partly because at lower temperatures, metabolism is reduced. This is also due to removing metabolically expensive features such as eyes, pigments, etc.
What are some special adaptations to depth?
1 - Bioluminescence
2 - Increased gape size and extensible stomach
Describe the angler fish and its adaptations to depth.
Have modified fin rays that they use as lures.
(modified dorsal ray that they wave back and forth to bring food to them)
Found in both mesopelagic and bathypelagic.
Much of the bioluminescence is produced from bacteria sequestered in photophores (light producing organs).
Other bioluminescence markers may be placed under the eye for control of light emission.
Why would bioluminescence be placed under the eye?
Allows for control of light emission. Can be used to attract prey and mates and closed when predators are near.
Describe increased gape size and a distensible stomach.
For really deep living fish where there is lots of space and not much food.
Increased gape size increases the range of prey sizes they can eat.
A distensible stomach can extend and hold a large meal. This will slowly digest the meal to increase time in which nutrients can be consumed.
Suborder. Notothenoids are polar region living fish which contain antifreeze proteins to survive sub-freezing temperatures.
These proteins are glycoproteins which stop ice crystals from forming.
Describe how antifreeze proteins work in Notothenoids.
The fish will have a blood supply running through them at -2°C. They will go to the ice to consume invertebrates and, upon touching ice, will have ice crystals form in their blood. Glycoproteins will then surround the ice crystals and stop them from getting larger, preventing damage to cells.
Which regions use antifreeze proteins?
Arctic and Antarctic.
What is supercooling?
These fish decrease the amount of particles in their blood (i.e. reduced platelets, proteins, etc.) and, in some cases, even rid themselves of Hemoglobin.
This is because if there are lots of particles in the blood, ice crystals will stick to these and conglomerate.
But, if these fish touch the ice outside, they will immediately freeze and die.
Only found in antarctic fish
Where do you find supercooling fish?
What are the issues that fish face in subterranean caves?
Caves have no light
Food density is low
What do fish not have to worry about in subterranean caves?
Pressure is normal since related to atmosphere.
Temperature is also stable.
Fish in subterannean caves usually lack what?
These fish are completely blind but, larvae will still have eyes.
These fish also lack scales, this is due to lack of predators.
Bear no pigmentation to reduce metabolic demand.
To make up for their lack of vision, cave dwelling fish have other enhanced senses, describe these.
Chemoreception (smell and taste) - often find food and each other by being good at detecting odours through the nose or enhanced taste buds. They have really receptive noses that can follow food gradients.
Mechanoreception: can detect mechanical vibrations in the water to find prey such as crustaceans. Detect small vibrations to find food.
How long can cave fish go without food?
Months. Their metabolism is slowed down.
What is an ephemeral pond?
Where are ephemeral ponds located?
What are the issues that fish face in ephemeral ponds?
Anoxia, large temperature extremes, lack of water.
Describe the issues of ephemeral ponds.
Lots of deserts will have small ponds which will be present during the rainy season.
Ponds however, are not connected to actual bodies of water so, the pond will eventually evaporate.
During evaporation, the water becomes very warm and anoxic. There are many answers to this issue.
What are the answers to evaporation of ephemeral ponds?
Accessory respiratory structures
As the dry season nears and temperature rise and anoxic conditions manifest, these two factors serve as spawning triggers for the adults to lay eggs.
These eggs, once fertilized, sink to the bottom and enter the diapausing phase.
These eggs can rest for 3-4 years and, when the rain returns, will trigger the egg to divide again in early spring to hatch and the fish will then mature as adults.
Describe accessory respiratory structures.
This is the case when the pond is not completely ephemeral.
Low oxygen is still an issue.
Different fish will have different adaptations to take in air to survive, such as gulping air or lungfish which can directly breathe air.
What is estivation?
Lungfish estivate, meaning they have a semi-resting state as adults.
Adults will go into the mud and rest until conditions improve. (occurs if temperatures are too high or oxygen too low)