I Fishes Biology B Coloration 1 2 3
I. Fishes - Biology B. • Coloration • • 1. 2. 3. 4. • • • Pigments in chromatophores Specialized cells in skin Many fishes can change colors rapidly by expanding or contracting pigment in chromatophores Structural colors – Produced by reflective crystals in iridophores (specialized chromatophores) Functions Warning 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 Countershading Dark top, light bottom Camouflage in open water
Warning Cryptic Disruptive Countershading
I. Fishes - Biology C. Locomotion • Most fishes swim using rhythmic contractions produced by bands of muscles – myomeres • • 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 • • 2. Lack swim bladder Generate lift with 1) Buoyant oily liver 2) Heterocercal tail 3) Rudder-like pectoral fins Rays and skates • • Generate lift with large pectoral fins Narrow tail plays minor role in swimming
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I. Fishes - Biology C. Locomotion 3. Bony fishes • • Swim bladder provides buoyancy Diversity in swimming styles 1) Eel-like – Undulation of body • Ex – Moray eel 2) Caudal – Propulsion with tail and body • Ex – Tuna 3) Pectoral – Tail contributes little • Ex – Surgeonfish 4) Dorsal/Anal – Tail used as rudder • Ex – Triggerfish 5) Other • Ex – Trunkfish
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I. Fishes - Biology D. Feeding 1. Sharks and Cartilaginous Fishes a. Bite pieces from large prey • Tiger shark – Diverse stomach contents • Great white shark – Wound and wait • Cookie cutter shark – Cut out chunks b. Ingest smaller prey whole • Nurse shark – Benthic invertebrates c. Filter plankton – Gill rakers • Whale shark – Warm • Basking shark – Cold • Megamouth shark • Manta ray
I. Fishes - Biology D. Feeding 2. Bony Fishes a. Capture large prey whole • Barracuda • Frogfishes b. Pickers - Ingest smaller prey whole • Butterflyfish, Slipmouth c. Grazers • Parrotfish • Filefish d. Filter plankton – Gill rakers • Anchovies • Sardines • Herrings
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I. Fishes - Biology E. Respiratory System 1. Irrigation of Gills a. • Chondrichthyes Force water over gills by • Swimming with mouth open • 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 b. Osteichthyes • Gills housed in common gill chamber • Openings covered by operculum on each side • Mouth opens/operculum closes & vice-versa
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I. Fishes - Biology E. Respiratory System 2. Structure of Gills • • 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 • 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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