Lecture 1 - Habitats - Special Habitats

Question 1

What are the main problems that arise with living at depth?

Answer 1

1 - Pressure
2 - Light
3 - Cold
4 - Lack of food
5 - lots of empty space (hard to find mates)

Question 2

Pressure increases linearly with depth at a rate of ______.

Answer 2

1 atm/10m

Question 3

Why can fish survive such high pressures?

Answer 3

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

Question 4

How do fish get around the lack of light?

Answer 4

1 - Fish get smaller eyes or lose eyes altogether

Question 5

Why is the loss of eyes an important feature at depth?

Answer 5

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

Question 6

What are other features that fish living at depth have lost?

Answer 6

Pigments, useless since they cannot be seen.

Question 7

What are features, related to metabolism, of fish at depth?

Answer 7

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.

Question 8

What are some special adaptations to depth?

Answer 8

1 - Bioluminescence

2 - Increased gape size and extensible stomach

Question 9

Describe the angler fish and its adaptations to depth.

Answer 9

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.
Produce bioluminescence.
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.

Question 10

Why would bioluminescence be placed under the eye?

Answer 10

Allows for control of light emission. Can be used to attract prey and mates and closed when predators are near.

Question 11

Describe increased gape size and a distensible stomach.

Answer 11

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.

Question 12

Describe notothenioidei.

Answer 12

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.

Question 13

Describe how antifreeze proteins work in Notothenoids.

Answer 13

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.

Question 14

Which regions use antifreeze proteins?

Answer 14

Arctic and Antarctic.

Question 15

What is supercooling?

Answer 15

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

Question 16

Where do you find supercooling fish?

Answer 16

Antarctic only

Question 17

What are the issues that fish face in subterranean caves?

Answer 17

Caves have no light

Food density is low

Question 18

What do fish not have to worry about in subterranean caves?

Answer 18

Pressure is normal since related to atmosphere.

Temperature is also stable.

Question 19

Fish in subterannean caves usually lack what?

Answer 19

Functional eyes.
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.

Question 20

To make up for their lack of vision, cave dwelling fish have other enhanced senses, describe these.

Answer 20

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.

Question 21

How long can cave fish go without food?

Answer 21

Months. Their metabolism is slowed down.

Question 22

What is an ephemeral pond?

Answer 22

Transient/temporary pond

Question 23

Where are ephemeral ponds located?

Answer 23

Deserts

Question 24

What are the issues that fish face in ephemeral ponds?

Answer 24

Anoxia, large temperature extremes, lack of water.

Question 25

Describe the issues of ephemeral ponds.

Answer 25

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.

Question 26

What are the answers to evaporation of ephemeral ponds?

Answer 26

Diapause
Accessory respiratory structures
Migration
Estivation

Question 27

Describe diapause.

Answer 27

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.

Question 28

Describe accessory respiratory structures.

Answer 28

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.

Question 29

What is estivation?

Answer 29

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)

Question 30

Describe migration.

Answer 30

This is when estivation in inadequate and these fish cannot diapause. These fish need to leave these conditions so, a number of fish can simply walk out, leave the pond and migrate to a nearby water body.
Snakehead can do this.

Question 31

What is the intertidal zone?

Answer 31

zone between tides, pertinent in marine systems. Located between low and high tide.

Question 32

What are the issues with living in the intertidal zone?

Answer 32

Temperature, less space, strong currents, tides buffet fish

Question 33

Describe the issues that arise in the intertidal zone for fish.

Answer 33

Plenty of space, cool water during high tide.
Then, low tide comes, pond dries up, reduced space to swim, sun comes out and the temperature increases dramatically.
Then, when the tide returns, the fish get buffeted.

Question 34

What are the adaptations to living in the intertidal zone?

Answer 34

Tough skin and enhanced scales.
Modification in fins to hold onto or cling to surfaces.
These fish tend to be eurythermal.

Question 35

Define eurythermal.

Answer 35

Fish that can withstand a broad temperature range.

ex: warm temps of low tide and colder temps. of high tide.