Transcript I. Fishes - Biology B. Coloration • Pigments in chromatophores • • • • Specialized cells in skin Many fishes can change colors rapidly by expanding or contracting pigment (usu.

I.
Fishes - Biology
B.
Coloration
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Pigments in chromatophores
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Specialized cells in skin
Many fishes can change colors rapidly by expanding or contracting
pigment (usu. melanins, carotenoids) in chromatophores
Hormonal and nervous control
Structural colors
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1.
Reflective crystals in iridophores (specialized chromatophores)
Functions
Aposematic coloration
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2.
Dangerous, poisonous, bad tasting
Cryptic coloration
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3.
Blend with environment – hide from predators, stalk prey
Disruptive coloration
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4.
Break up outline of individual fish – confuse predators
Obliterative countershading
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Dark top, light bottom
Camouflage in open water
Aposematic
Disruptive
Cryptic
Countershading
I.
Fishes - Biology
C.
Locomotion
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Most fishes swim using rhythmic contractions produced
by bands of muscles – myomeres
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1.
Myomeres connect to backbone for support
Swimming muscles make up large percentage of body
weight (up to 75% in tunas and active swimmers)
Sharks
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2.
Lack swim bladder
Generate lift with
1) Buoyant oily liver
2) Heterocercal tail
Rays and skates
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Generate lift with large pectoral fins
Narrow tail plays minor role in swimming
I.
Fishes - Biology
C.
Locomotion
3.
Surgeonfish
Bony fishes
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Swim bladder provides buoyancy
Diversity in swimming styles
1) Eel-like – Undulation of body
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Ex: Moray eel
2) Caudal – Propulsion with tail and body
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Ex: Tuna
3) Pectoral – Tail contributes little
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Ex: Surgeonfish
4) Dorsal/Anal – Tail used as rudder
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Ex: Triggerfish
5) Other
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Ex: Trunkfish
Triggerfish
Fig. 10-21
I.
Fishes - Biology
D.
Respiratory System
1.
Irrigation of Gills
a.
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Chondrichthyes
Force water over gills by
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Swimming with mouth open
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Gill pump
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Each gill lies in own gill chamber
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Open to outside through gill slits
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First pair of gill slits modified as spiracles
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Open/Close mouth to ventilate gills
b. Actinopterygii/Osteichthyes
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Gills housed in common gill chamber
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Openings covered by operculum on each side
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Mouth opens/operculum closes & vice-versa
I.
Fishes - Biology
D.
Respiratory System
2.
Structure of Gills
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3.
Gills supported by cartilaginous or bony gill arches
Each gill arch bears two rows of gill filaments
Each gill arch has projections called gill rakers
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Filter out potentially damaging coarse particles
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May be used for filter feeding in some species
Each gill filament contains rows of lamellae
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Contain dense networks of capillaries
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Increase surface area for gas exchange
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Greater numbers of lamellae in active swimmers
Gas Exchange
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Occurs by diffusion
Countercurrent exchange
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Increases efficiency of gas exchange
Fig. 10-23
Fig.
10-25