Osteichthyes Flashcards
What percentage of vertebrates are the bony fish?
~50%
What are the two groups of osteichthyes?
Actinopterygii = ray-finned fish
Sarcopterygii = lobe-finned fish
Give some facts about the osteichthyes
> 30,000 species
> 95% of all fish
First appeared ~400 MYA
Radiated in the Devonian to form two groups
Give some features of the non-teleosts actinopterygians
Regarded as basal actinopterygians
Have a cartilaginous skeleton as they have lost endochronal bone
Have lost scales
Upper jaw isnt fused to the cranium
Have a gas bladder
Give some examples of non-teleosts actinopterygians
Sturgeons:
- 1-6m long
- Benthic
- Can either live in marine water and breed in freshwater or just live in freshwater (need freshwater to breed)
- Have scutes
- Protrusible jaw - used for suction feeding
- Long lived and are late maturers
- Vulnerable due to eggs being harvested for caviar and migratory routes often being blocked (dams)
**Paddlefish **
- Paddle detects electrical impulses
- Only have two species - 1 is now extinct
Give some features of the teleosts actinopterygians
Had rapid diversification early in history due to duplication of Hox genes
Jaw mobility was important in radiation
For jaw mobility, pre-maxillia and maxilla are not attached to the cranium
Specialisation of feeding mechanisms
Flexibility of bones of skull and jaws exploit range of prey
Jaws - suction device increased volume of buccal cavity
How much as jaw protrusion increased over time in teleosts?
Early creteaceous had no jaw protrusion
Then became 8.2% of standard length in the late Cretaceous
Then became 13.3% in the Exocene
Now in extant species, it is 21.4% of the standard length
What animal has a ‘raptorial’ pharyngeal jaw?
The moray eel
Has a second jaw that rests in the throat
This is then launched forward to grasp prey and help move down the oesophagus
Has to use this method as lives in crevices so it is harder to suction feed
Give some features of the teleosts
Have a homocercal tail
Have small scales
Fusiform shape
Have a rounded eye lens - use muscles to move the lens forwards and backwards to focus
Most are oviparous
Have a lateral line, operculum, swim bladder, gill slits
Where do most fish get their power for swimming from?
Most fish power swimming with muscles in the posterior trunk
Muscle blocks act antagonistically in the trunk (one contracts whilst another relaxes)
Very few rely on fins
Give some examples of teleosts that have different fin morphologies
Leafy sea dragon:
-projections along the body are not fins
- the sea dragon fins are tiny
Flying fish:
- have elongated pectroal fins for gliding
Guppies:
- males have elabroate/colourful fins for sexual selection
What is the lateral line in fish for?
Also can be known as the neuromast organ
Detects water displacement/trubulence
Often found along the body of the fish
Although, fish that form dense shoals have lateral line organs in their head to stop interference from other members
Give some examples of intelligence tests done in teleosts
Cleaner wrasse fish:
-passed the self-recognition test (placed a spot on the fish and it tried to wipe it off)
-then put a photo of itself and another fish and it only tried to attack the picture of the other fish
Sea bream fish:
-trained sea breams to follow a specific diver for food
- swapped the divers clothes and the fish followed the diver wearing the original clothing
- put the divers in the same clothes and the fish got confused
What is the swim bladder? What did it evolve from?
Swim bladder means they can stay in the water column without using as much energy
Evolved from the primitive fish lung which was used for respiration - this was found ventrally
Then became dorsal swim bladder
Swim bladder is homologous with the lungs of the sarcopterygians
How does the swim bladder work?
Fish want to be in neutral buoyancy - means they expend less energy
When they go deeper, the increased pressure causes a decrease in size of the swim bladder this means they have to increase the amount of gas in the swim bladder to put them into neutral buoyancy
As they get closer to the surface the opposite happens
What is counter-current exchange?
Water flows over the gills in one direction
Blood flows in the opposite direction
Done by buccopharyngeal pumping
What is ram ventilation?
No buccopharyngeal pumping so need to have mouth open all the time
Found in tuna and pelagic fish
What is regional heterothermy in fish?
Muscles are 10C higher than surrounded water
This is typical of active predaceous animals
What are anabantid fish?
Actinopterygians teleosts that are obligate air breathers
They have gills but need to gulp atmospheric air:
- done by labyrinth organ
- gills are not good enough so would die without air gulping
What are the different types of eels? What dintinguishes them?
European/North African eels
American eels
Dintinguished by number of vertebrae and mtDNA (mitochondrial DNA)
What does catadrmous means?
Live mostly in the freshwater and go into marine envrionment to breed and die after breeding
Where were Europeans eels found to breed?
Found to breed in the Sargasso sea (same as American eels)
Hatch as leptocephalus larvae and turn into glass eels before returning to freshwater (takes around 3 years to journey back from Sargasso sea to freshwater)
What IUCN rating are Europeans eels? Why?
Critically endangered
From:
-overfishing
-trade
-pollution
-dams causing disruption during migration
What groups come under the sarcopterygians?
Lungfish (3 genera of them)
Coelacanths
Those that gave rise to the tetrapods (known as tetrapodomorph fish)
Lungfish are more closely related to the tetrapods than the coelacanths are
