Osteichyes (Bony fish) Flashcards
What are the two major groups within Osteichyes?
- Actinopterygii (Ray-finned fish)
- Sarcopterygii (Lobe-finned fish)
Radiated into these two groups during the devonian period
How do the fins of actinopterygii and sarcopterygii differ?
- Actinopterygii have fin rays of dermal origin (comes from skin)
- Sarcopterygii have a more substantail fin
What are the actinopterygii?
Ray-finned fish
What are the Sarcopterygii?
Lobe-finned fish
Which group of osterichyes gave rise to the tetrapods?
Sarcopterygii
What percantage of fish are osteichyes?
Over 95%
What is the main feature of osteichyes?
Endochondral bone - Cartilage replaced by bone
Non-teleost actinopterygians: What are their main features?
- Secondarily lack endochondral bone (cartilagenous skeleton)
- Loss of scales
- Upper jaw isn’t fused to cranium
- Gas bladder
Examples of Non-teleost actinopterygians: Sturgeon
- 1-6+ m
- Benthic, MW (breed in FW), FW
- Scutes (no scales)
- Protrusible jaw => suction feeding
- Long lived/late maturing
- Heterocercal tail (asymmetrical)
- Harvested for their eggs (caviar)
Examples of Non-teleost actinopterygians: Paddlefish
- Paddle at front of head
- Paddle detects electrical impulses (similar to ampullary organs of sharks)
- 2 species (one is a filter feeder in america, the other is extinct - from china)
- Under threat - spawning grounds blocked - eggs collected for caviar
Teleost Actinopterygians: Main features
- Additional duplication event in hox genes (7)
- Rapid diversification in early history
- Jaw mobility allows adaptations
How is the Teleost jaw specialised?
- Mandible
- Premaxilla & Maxilla not attached to cranium
- Flexible
- Sucks prey towards mouth - increased the volume of buccal cavity
- Can protrude jaw by over 20%
- Jaw protrusion has increased during the evolution of the teleosts
- see image 3 for structure of jaw
What formed the pharyngeal jaws?
- Modified branchial arches
- (Modified gill arches)
- Modified for food processing
How have pharyngeal jaws enabled the diversification of feeding habits?
- Freed up oral jaws from food manipulation
- Pharyngeal jaws process food by ripping / tearing / chewing etc
- Oral jaws can be modified for different feeding modes
How are the jaws of the Moray eel so modified?
- Extreme case of pharyngeal jaws (secondary jaw)
- Raptorial pharyngeal jaws
- jaws can be shot out to grasp prey and pull back into mouth.
- Is an adaptation to living in crevices where suction feeding is restricted.
Some examples of diverse skull shapes in osteichyes
- Cichlidae (cichlids)
- Labridae (wrasses)
diversified due to developpment of pharyngeal jaws - allowing diversity of feeding habits.
What kind of tail do osteichyes have?
Homocercal tail (caudal fin)
What is the structure of the homocercal tail and what is it used for?
- symmetrical
- Used for steering (not for lift)
Main features of osteichyes body
- Small scales
- Operculum covers gills
- Anal fin
- Pelvic fin
- Fin ray
- Gill slits
- Swim bladder
- Nostril
- Fusiform shape
How do the majority of bony fish power movement?
- Most fish power movement with muscles in posterior trunk
- Few rely on fins alone
What are some examples of fin modifications in bony fish?
- Flying fish - enlarged pectoral fins
- Guppy - sexual dimorphism - male have modified anal fin (gonopodium) used for fertilisaiton
- Leafy sea dragon small fins - lots of extra protrusions that aren’t fins
What kind of reproduction do most telesost exhibit?
Oviparous (egg laying)
What do the neuromast organs on bony fish detect and where are they located?
- Located on the lateral line
- Used for detection of signals from the water (water displacement, turbulence etc)
- Fish that form dense sholas have lateral line organs in the head. (don’t have neuromasts in lateral line - too much stimulation)
Self recognition test in bony fish
- Cleaner wrasse
- Put a mark on the fish, place it in front of the mirror and if the fish tries to rub off the mark they show self recognition.
- Showed photographs - also showed self recognition.
What is a Swim bladder used for?
To maintain bouyancy
How has the swim bladder evolved?
- Originally functioned as a lung - basal lineages - Basal actinopterygians- lungs
- Lung has become dorsally placed - swim bladder is dorsal
- In some the swim bladder is still attached to gut, others have lost this attachment
How does the swim bladder maintain bouyancy?
- Reduced pressure near surface - bladder is large
- Increased pressure with depth - need to increase volume of swim bladder by adding gas.
How do fish alter the size of their swim bladder to maintain bouyancy?
- Fish with swim bladder attached to gut gulp air and increase gas or burp out air to decrease.
- Fish without attachment get rid of gas via blood (oxygen diffuses in or out of blood depending if they want to increase or reduce swim bladder size)
How do fish use gills for respiration?
- Countercurrent exchange
- Out through the operculum
- Buccopharyngeal pumping (movement of mouth for continued water flow)
- Blood flows in opposite direction to the water - maximises gas exchange
What is buccopharyngeal pumping?
Movement of mouth for continued water flow
How do fish without buccopharyngeal pumping get water to flow over gills ?
- Some fast swimming fish have mouth open at all times instead of buccopharyngeal pumping.
- Ram ventilation
- e.g. tuna and some pelagic fish
Some can switch between have mouth open (when moving) and Buccopharyngeal pumping when more static.
What is Regional heterothermy?
- Heating muscles
- Countercurrent system with blood vessels - blood from muscles is warmer than blood coming from gills so when they cross heat is exchanged.
- Seen in some bony fish and cartilaginous fish too
Most bony fish (actinopterygians) use gills but some are air breathers, give examples of adaptations for this.
- Enlarged lips for gas exchange
- Vascularised anus for respiration
- Anabantid fishes obligate air breathers e.g. dwarf gourami. Have a labyrinth organ in head for adaptation
Why are eels unusual (structure)?
- Lost pelvic fins
- Loss of scales
What is unusual about european eel migration
- Schmidt - tried to find where European eel larvae were. Found them in sargasso sea.
- Leptocephalus larva (marine water)
- Glass eel (MW FW)
- Elver (FW)
- Migration - 5000 - 10000 km
- Critically endangered - harvested, pollution etc
- Catadromous (freshwater adult, marine to breed)
Sarcopterygians: what are the three groups?
- Lungfish
- Coelacanths
- Those that gave rise to the tetrapods
Lungfish are more closely related to to tetrapods than the coelacanths are
Lungfish - when do they use their lungs?
- Mainly use gills
- Can use lungs if needed
- African and South American dependent on lungs
Where are lungfish found?
Africa, South America and Australia
How have african lungfish been observed using their fins?
Walking and bounding using reduced pectoral fins
How do male SA lungfish oxygenate embryos ?
Male SA lungfish have extensions that can be vascularised - oxygenates nest where developing embryos are
How are lungfish adapted to habitats that dry out?
Lives in area prone to drying - burrows produces mucus and cocoons - goes into a resting state waiting for condition to improve (aestivation)
How do Coelacanths feed?
Suction feeders
What is interesting about early coelacanth discovery?
Thought to have gone extinct 80 MYA
Caught in fishing
Marjorie Courtney-Latimer discovered live coelacanth
Coelacanth features
- Large (2 m), deep water, nocturnal
- Don’t use fins as props when moving around
- Vestigial fat-filled lung (buoyancy aid)
- Retain urea
- Electroreceptor organ - detect electrical
Coelacanth reproduction
- Viviparous - internal fertilisation, birth live young.
