Bony Fishes

Front 1

Osteichthyes

Back 1

bony fish
Devonian 400 million years ago
largest group of living vertebrates

Front 2

Sarcopterygii

Back 2

Worldwide, there are six species of lungfishes

Front 3

Coelacanth

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Hide in caves 100-500m deep during the day and come out to predate at night. Up to 2m in length and 90kg living up to 60 years. Very small remnant populations left

Front 4

Actinopterygii

Back 4

ray-finned fishes with webs of skin supported by bony spines. Majority of bony fish -96%
eg porcupine fish

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Locomotion

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Swimming occurs due to contractions of muscles on one side of the body and simultaneous relaxation of those on the opposite side
When moving successive points of the body of a fish alternatively oscillate from side to side

Front 6

Cruising

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continuous swimming, red muscle fibres, contract slowlyproducing low power output, high aerobic demandsrequiring continuous O2supply. It is richly supplied with blood vessels to deliver the O2.

Front 7

Burst swimming

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white muscle fibresused, contracts rapidly with high power output, fatigue rapidly, anaerobic energyoften uses local cellular glycogen. Rapid use of energy stores leads to accumulation of metabolites, often as lactic acid

Front 8

Benthic

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usually depressed from top to bottom eg rays, flounder. Others may be almost triangular in cross section with a flattened abdomen eg. Hiwihiwi, blue cod
Usually well camouflaged and feed on relatively immobile or unaware prey

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Streamlined

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These are constantly moving, fast swimming pelagic fish eg. Tuna, kingfish
Fusiform shape to cut through the water
No projections therefore little resistance
Dorsal and anal fins can fit into a groove to allow fast swimming

Front 10

Reef fish

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Laterally compressed eg Red Moki, parore
Relatively slow moving with good camouflage and remain near the reef throughout their life
Hard to see from front on

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Other body shapes

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•Some weed dwelling spp are very slender to reduce the effects of water movement. Eg. Butterfish.
•Clingfish attach to substrate.
•Crevice dwelling spp laterally compressed and wedge themselves in narrow gaps

Front 12

Anguilliform

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•Alternate contractions and relaxation of muscles along length of body.
•S-shaped curve of body.
•Main thrust from tail especially if laterally compressed.
•Eels, rock cod, seven-gill shark

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Carangiform

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•Movement comes from rear third of body.
•Tail main source of power.
•Most pelagic and reef fish swim in this way.
•Eg. Kahawai, kingfish.
•Tuna uses only tail with narrow caudal peduncle, keels and body remains rigid when swimming.

Front 14

Labriform

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•Pectoral fins used for swimming.
•Body muscles and tail used only when short bursts of speed are required.
•Generally slow.
•Labrids, butterfish, blue cod.
•Synchronised flapping of broad, rounded pectoral fins.
•Stingray beats pectoral fins synchronously in a wave-like motion, whereas the eagle ray beats asynchronously.

Front 15

Balistiform

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•Dorsal and anal fins provide the power.
•Can move forward or backwards depending on direction of fin movement.
•Used by leatherjackets, john dory, and seahorse.
•Not a fast swimming method

Front 16

Locomotion

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•Fish turn mainly using their pectoral and ventral fins.
•The pectoral fins are used for breaking in all but balistiform species which reverse their anal and dorsal fin direction.

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Swim bladder

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•Needed to help fish maintain position in water column
•5% body volume in marine teleosts
•7% body volume in freshwater teleosts
•Benthic fish have no swim bladder (or greatly reduced in size and function)
•Tuna have no swim bladder as move too fast through water column for swim bladder to keep up.
•Needs to maintain a constant volume at differing depths.
•Gas needs to enter swim bladder on descent and exit on ascent.
•Gas does not enter or exit through the swim bladder wall and needs a specific structure to allow this to occur

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Physostomes

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•Primitive teleosts
•Pnuematic duct allows a connection between the gut and the swim bladder
•Gulp air at surface to fill swim bladder and burp gas upon ascent.
•Functions as float but can also act as a lung

Front 19

Physoclistic fish

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•More advanced teleosts
•Haemoglobin carries oxygen in the blood (HbO2).
•This arterial oxygen is at low pressure -0.21atm -and may need to be transferred into the swim bladder which can have a high pressure -101atm at 1000m. So huge pressure gradient to overcome

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Physoclistic fish

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•4 structures and their functions need to be understood.
•Swim bladder-where the gas is held to control buoyancy
•Gas gland -releases lactic acid to cause haemoglobin to release oxygen in the rete mirabile
•Rete Mirabile
•Ovale

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Rete mirabile

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•Latin = marvellous net
•O2pressure builds up on venous side of rete mirabile. This free O2diffuses from the venous side of the rete mirabile to the incoming arterial blood of the rete mirabile.
•O2remains trapped within the rete mirabile and pressure increases as more O2is released from haemoglobin by lactic acid.
•When O2pressure in rete mirabile exceeds that of swim bladder it diffuses across into the swim bladder

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Ovale

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•Ovale vasodilates (opens up) blood vessels when gas needs to be released from the swim bladder.
•Gas at high partial pressure diffuses from the swim bladder into the blood vessels which have low partial pressures.
•When enough gas has been released blood vessels vasoconstrict (close up) so no further gas can diffuse out

Front 23

deep sea fish

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Deep sea fishes have oily deposits in swim bladder which does not compress at depth and maintains a more constant buoyancy.
•These fish still require a long rete mirabile due to high pressures at these depths.
•Deep sea fish also reduce the amount of bone in their skeleton.