Fish

Question 1

List 5 physical properties of water that make it difficult to live in.

Answer 1

1. Higher density
2. High viscosity
3. Low oxygen
4. Higher heat conductivity
5. Higher electrical conductivity

Question 2

The chondrichthyans are made up of 2 major groups. What are they?

Answer 2

1. Selachimorpha: the sharks

2. Batoidea: the rays

Question 3

Approx. how many species of a) sharks and b) rays are there?

Answer 3

a) 350

b) 500

Question 4

There are 2 major extant groups of sarcopterigyan. What are they and how many species are there?

Answer 4

1. Coelacanth: 2 species

2. Lungfish: 3 species

Question 5

How many species of actinopterygian are there?

Answer 5

~29,000

~20,000 of these are teleosts.

Question 6

Sharks have septal gills. What does this mean?

Answer 6

Structures called septa support the gill slits.

Basically the gills are flat.

Question 7

Osteichthyans (bony fish) have opercular gills. What does this mean?

Answer 7

They have no septa: instead gill bars anchor the gill filaments. The operculum is a structure that protects the gills.

Basically the gills are like plates that lay on top of each other.

Question 8

In osteichthyans expiration occurs through a single gill slit. True or false?

Answer 8

True.

Question 9

Agnathans have what kind of gills?

Answer 9

Pouched gills: these have pores rather than slits and use tidal flow.

Question 10

The gill bars of osteichthyans have 2 filaments. What are they and what is their purpose?

Answer 10

Primary and secondary lamellae: they increase the surface area for gas exchange.

Question 11

In osteichthyans gas exchange actually occurs where?

Answer 11

Over the secondary lamellae.

Question 12

The gill filaments have 2 arteries. What are they, what do they do?

Answer 12

1. Afferent vessels: come from the heart, blood is deoxygenated and flows to the gills.
2. Efferent vessels: go to the heart, blood is oxygenated and must be pumped around the body.

Question 13

There are 2 main methods of ventilating the lungs. What are they?

Answer 13

1. Buccal pumping

2. Ram ventilation

Question 14

Define buccal pumping.

Answer 14

‘Breathing with the cheeks’: the animal moves the floor of its mouth in a rhythmical manner. This generates a positive pressure across the gills.

Question 15

Define ram ventilation.

Answer 15

Water flows in through the mouth and passes out over the gills.

Question 16

In which species is ram ventilation most common?

Answer 16

Pelagic fast swimmers. For example sharks must never stop swimming as they would sink, so they use ram ventilation.

Question 17

Many fish switch between buccal pumping and ram ventilation. True or false?

Answer 17

True.

Question 18

Many fish are facultative air-breathers as an adaptation to living in stagnant water or ephemeral pools. Name 2 species that are obligate air breathers.

Answer 18

African lungfish and anabantids.

Question 19

The lungs did not originally develop for gas exchange. What was their original function?

Answer 19

The lungs developed from the pharyngeal end of the digestive tract. It functioned as a swim bladder for buoyancy. There was no gas exchange, it was simply an air-filled pouch that achieved neutral buoyancy as it reduced the fish’s mass.

Question 20

There are 2 types of fish with different swim bladders. What are they?

Answer 20

1. Physostomous fish

2. Physoclistous fish

Question 21

What is a physostomous fish?

Answer 21

The ancestral condition: the swimbladder is still attached to the gut, so fish gulp in and burp out air to regulate their buoyancy at depth. These fish commonly live in shallow water. They burp out air as they ascend.

Question 22

What is a physoclistous fish?

Answer 22

The swimbladder is no longer attached to the gut. They control the amount of gas in their swim bladders via abundant capillaries and glands. These fish are also able to use their swimbladders to make and detect sounds.

Question 23

How do physoclistous swimbladders work exactly? Give 3 steps.

Answer 23

1. Lactic acid accumulates in the blood
2. Blood fills the capillaries producing counter-current flow
3. O2 diffuses into the swimbladder

Question 24

What is the capillary structure called?

Answer 24

The rete mirabile

Question 25

How do sharks achieve neutral buoyancy when they have no swim bladders?

Answer 25

Their liver has a v. high oil content which is less dense than water.

Question 26

Describe how the swimbladder can be used to improve hearing?

Answer 26

The swimbladderis connected to the inner ear by the Weberian apparatus, a structure derived from the vertebrae. This increases the sensitivity to water pressure at depth.

Question 27

Give examples of fish that use their swimbladders for hearing.

Answer 27

Common carp and catfish.

Question 28

Define the lateral line system.

Answer 28

A system that detects pressure changes and vibrations in the water. This is a supplement to vision and hearing in primary aquatic animals, i.e. those that have never left the water.

Question 29

What is the integral unit of the lateral line system?

Answer 29

The neuromast: a mechanoreceptive organ that senses mechanical changes in water.

Question 30

The neuromast is covered in hair cells. Describe the hair cells.

Answer 30

They are covered in jelly-like cupula. They are basically modified epithelial cells that are sensitive to NTs. They are the mechanoreceptors that make up the neuromast organ.

Question 31

In some fish the lateral line system has been modified to detect electricity. True or false?

Answer 31

True: most electric fish use electricity for sensory purposes and communication.

Question 32

Give examples of a strongly electric fish that use electricity to stun their prey.

Answer 32

The electric eel, the torpedo ray

Question 33

Most chondrichthyans can sense, but not use, electricity. True or false?

Answer 33

True.

Question 34

Describe from electric fish produce electricity.

Answer 34

Electrocytes, modified muscle cells, are able to generate ion flow across cells. These cells are packed in stacks and act as batteries. The electrocytes are full of mitochondria as this is an energy expensive process.

Question 35

There are 2 types of electroreceptor in passive electrolocation. In which species are they found?

Answer 35

1. Ampullary: sharks have these. | 2. Tuberous and ampullary receptors: weakly electric fish have these.

Question 36

How does a) weak and b) strong electric ability differ?

Answer 36

a) Weak = passive electrolocation, whereby fish only detect the electricity of others. b) Strong = active electrolocation, fish generate their own electric fields and detects nearby objects when they distort this field.

Question 37

Describe the electroreception organ in sharks.

Answer 37

The ampullae of Lorenzini: jelly-filled canals filled with ampullary receptors act as voltmeters detecting the electric fields of nearby prey items.

Question 38

Most fish are ectothermic. What is regional endothermy?

Answer 38

The conservation of metabolic heat using a countercurrent heat exchange system in the blood. Usually takes place over muscles/sensory organs etc., not across the whole body. This maintains a high body temp. without an elevated energy cost.

Question 39

Which species use regional endothermy?

Answer 39

Large, pelagic species: sharks, tuna and billfishes.

Question 40

Regional endothermy evolved convergently. What 2 mechanisms does it arise by?

Answer 40

1. Billfish heat their eyes and brain | 2. Sharks and tuna heat their swimming muscles

Question 41

What does a) stenohaline and b) euryhaline mean?

Answer 41

a) Can tolerate small changes in salinity (most fish) | b) Can tolerate large salinity changes

Question 42

Freshwater fish are hyperosmotic. What does this mean?

Answer 42

They gain water and lose salt. This is because they are adapted to low salt conditions.

Question 43

Marine fish are hyposmotic. What does this mean?

Answer 43

They lose water and gain salt. This is because they live in high salinity.

Question 44

How are sharks hyposmotic?

Answer 44

Their blood has a higher water concentration (osmotic potential) than seawater. Thus water diffuses out of their bodies and into the water.

Question 45

What problems do sharks face in freshwater?

Answer 45

Freshwater has a higher osmotic potential than seawater, and higher than the blood of the shark. This means too much water would diffuse in to their bodies. That's bad.

Question 46

Describe the circulatory system of fish.

Answer 46

They have a two-chambered heart that pumps blood in a single closed loop around the body.