B5 vertebrates Flashcards
Teleoost phylogeny
Reduction in bony elements
Shifts in position and use of dorsal fin
Shifts in placement and function of paired fins
Caudal fin and gas bladder modifications
Modifications to feeding apparatus
Interrelated trends
Increased speed and feeding capability
No significant loss of defensive structures
Diversity of swimming types/morphology
Ancestral teleosts
Herring/salmons = simple fin configurations, single dorsal/anal fin, rocket-shaped form, tend to only have ray fins
Derived teleosts
Seabass/triggerfish/bass = more fins, diversification in morphology, diversity body forms (reflects feeding habits/habitats), they have spines.
Lower teleosts (herring)
Ossified vertebrae: 60-80
Vertebral accessories: many
Bones in skull: many
Bones/rays in tail: many
Fin rays in paired fins: >6
Scales: cycloid (heavy)
Higher teleosts (seabass)
Ossified vertebrae: 20-30
Vertebral accessories: few
Bones in skull: few
Bone/rays in tail: few
Fin rays in paired fins: <6
Scales: ctenoid (light)
Fin rays
Soft, not pointed, segmented, usually branched, bilateral
Spines
Hard and pointed, unsegmented, unbranched, solid
Caudal fin
In fossil actinopterygians
Reduced symmetry, reduction in bony elements or fusion of them to form stronger, solid plates.
Gas bladder
Arose as breathing or buoyancy device.
Living (gar) and basal teleosts (herring) = Physostomous (gas released through pneumatic duct).
Derived teleosts (seabass) = Physoclistous (gas exchanged across rete mirable).
How snapper eats
Mandible, premaxilla, maxilla
Premaxilla and maxilla are fused together in eel and hinged at the back so he can only snap. Whereas in a snapper (or more advanced teleosts) the maxilla swings forward when the jaw opens, this also pushes the premaxilla forward. This jaw protrusion creates a large area and allows for some suction.
Cranium lifts up, operculum pushes out, negative pressure, maxilla swings out, premaxilla is pushed forwards. Creates directed negative pressure (sucking forces).
Pharyngeal jaws/teeth
At the back of the throat, they ground up prey (molluscs, crustaceans) which help the fish swallow. They can also be used for filter feeding in some occasions.
Anguiliform
Like an eel, with undulating motion. Long/thin fish, often without a tail. Also in larval fish. Thrust from sides creates drag.
Subcarangiform
Cod, some sharks. Caudal fin isn’t very tall, moving towards oscillations.
Carangiform
Mackerel, jacks. Last 3rd of fish does most of the work. tail is taller and stiffer.
