Fishes - Biology

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• Fishes - Biology
• Coloration
• Pigments in chromatophores
• 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
• Reflective crystals in iridophores (specialized
  chromatophores)
• Functions
• Aposematic coloration
• Dangerous, poisonous, bad tasting
• Cryptic coloration
• Blend with environment hide from predators,
  stalk prey
• Disruptive coloration
• Break up outline of individual fish confuse
  predators
• Obliterative countershading
• Dark top, light bottom
• Camouflage in open water

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Aposematic
Disruptive
Countershading
Cryptic
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• Fishes - Biology
• Locomotion
• Most fishes swim using rhythmic contractions
  produced by bands of muscles myomeres
• Myomeres connect to backbone for support
• Swimming muscles make up large percentage of body
  weight (up to 75 in tunas and active swimmers)
• Sharks
• Lack swim bladder
• Generate lift with
• Buoyant oily liver
• Heterocercal tail
• Rays and skates
• Generate lift with large pectoral fins
• Narrow tail plays minor role in swimming

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• Fishes - Biology
• Locomotion
• Bony fishes
• Swim bladder provides buoyancy
• Diversity in swimming styles
• Eel-like Undulation of body
• Ex Moray eel
• Caudal Propulsion with tail and body
• Ex Tuna
• Pectoral Tail contributes little
• Ex Surgeonfish
• Dorsal/Anal Tail used as rudder
• Ex Triggerfish
• Other
• Ex Trunkfish

Surgeonfish
Triggerfish
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Fig. 10-21
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• Fishes - Biology
• Respiratory System
• Irrigation of Gills
• Chondrichthyes
• Force water over gills by
• Swimming with mouth open
• Gill pump
• Each gill lies in own gill chamber
• Open to outside through gill slits
• First pair of gill slits modified as spiracles
• Open/Close mouth to ventilate gills
• Actinopterygii/Osteichthyes
• Gills housed in common gill chamber
• Openings covered by operculum on each side
• Mouth opens/operculum closes vice-versa

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• Fishes - Biology
• Respiratory System
• Structure of Gills
• 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
• Filter out potentially damaging coarse particles
• May be used for filter feeding in some species
• Each gill filament contains rows of lamellae
• Contain dense networks of capillaries
• Increase surface area for gas exchange
• Greater numbers of lamellae in active swimmers
• Gas Exchange
• Occurs by diffusion
• Countercurrent exchange
• Increases efficiency of gas exchange

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Fig. 10-23
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Fig. 10-25