Flashcards in Fish Deck (46):
List 5 physical properties of water that make it difficult to live in.
1. Higher density
2. High viscosity
3. Low oxygen
4. Higher heat conductivity
5. Higher electrical conductivity
The chondrichthyans are made up of 2 major groups. What are they?
1. Selachimorpha: the sharks
2. Batoidea: the rays
Approx. how many species of a) sharks and b) rays are there?
There are 2 major extant groups of sarcopterigyan. What are they and how many species are there?
1. Coelacanth: 2 species
2. Lungfish: 3 species
How many species of actinopterygian are there?
~20,000 of these are teleosts.
Sharks have septal gills. What does this mean?
Structures called septa support the gill slits.
Basically the gills are flat.
Osteichthyans (bony fish) have opercular gills. What does this mean?
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.
In osteichthyans expiration occurs through a single gill slit. True or false?
Agnathans have what kind of gills?
Pouched gills: these have pores rather than slits and use tidal flow.
The gill bars of osteichthyans have 2 filaments. What are they and what is their purpose?
Primary and secondary lamellae: they increase the surface area for gas exchange.
In osteichthyans gas exchange actually occurs where?
Over the secondary lamellae.
The gill filaments have 2 arteries. What are they, what do they do?
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.
There are 2 main methods of ventilating the lungs. What are they?
1. Buccal pumping
2. Ram ventilation
Define buccal pumping.
'Breathing with the cheeks': the animal moves the floor of its mouth in a rhythmical manner. This generates a positive pressure across the gills.
Define ram ventilation.
Water flows in through the mouth and passes out over the gills.
In which species is ram ventilation most common?
Pelagic fast swimmers. For example sharks must never stop swimming as they would sink, so they use ram ventilation.
Many fish switch between buccal pumping and ram ventilation. True or false?
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.
African lungfish and anabantids.
The lungs did not originally develop for gas exchange. What was their original function?
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.
There are 2 types of fish with different swim bladders. What are they?
1. Physostomous fish
2. Physoclistous fish
What is a physostomous fish?
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.
What is a physoclistous fish?
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.
How do physoclistous swimbladders work exactly? Give 3 steps.
1. Lactic acid accumulates in the blood
2. Blood fills the capillaries producing counter-current flow
3. O2 diffuses into the swimbladder
What is the capillary structure called?
The rete mirabile
How do sharks achieve neutral buoyancy when they have no swim bladders?
Their liver has a v. high oil content which is less dense than water.
Describe how the swimbladder can be used to improve hearing?
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.
Give examples of fish that use their swimbladders for hearing.
Common carp and catfish.
Define the lateral line system.
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.
What is the integral unit of the lateral line system?
The neuromast: a mechanoreceptive organ that senses mechanical changes in water.
The neuromast is covered in hair cells. Describe the hair cells.
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.
In some fish the lateral line system has been modified to detect electricity. True or false?
True: most electric fish use electricity for sensory purposes and communication.
Give examples of a strongly electric fish that use electricity to stun their prey.
The electric eel, the torpedo ray
Most chondrichthyans can sense, but not use, electricity. True or false?
Describe from electric fish produce electricity.
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.
There are 2 types of electroreceptor in passive electrolocation. In which species are they found?
1. Ampullary: sharks have these.
2. Tuberous and ampullary receptors: weakly electric fish have these.
How does a) weak and b) strong electric ability differ?
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.
Describe the electroreception organ in sharks.
The ampullae of Lorenzini: jelly-filled canals filled with ampullary receptors act as voltmeters detecting the electric fields of nearby prey items.
Most fish are ectothermic. What is regional endothermy?
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.
Which species use regional endothermy?
Large, pelagic species: sharks, tuna and billfishes.
Regional endothermy evolved convergently. What 2 mechanisms does it arise by?
1. Billfish heat their eyes and brain
2. Sharks and tuna heat their swimming muscles
What does a) stenohaline and b) euryhaline mean?
a) Can tolerate small changes in salinity (most fish)
b) Can tolerate large salinity changes
Freshwater fish are hyperosmotic. What does this mean?
They gain water and lose salt. This is because they are adapted to low salt conditions.
Marine fish are hyposmotic. What does this mean?
They lose water and gain salt. This is because they live in high salinity.
How are sharks hyposmotic?
Their blood has a higher water concentration (osmotic potential) than seawater. Thus water diffuses out of their bodies and into the water.
What problems do sharks face in freshwater?
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.