Fishes - Biology Coloration Pigments in chromatophores Specialized cells in skin

1. 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

2. Aposematic Disruptive Countershading Cryptic

3. 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

4. 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

5. Fig. 10-21

6. 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

8. 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

9. Fig. 10-23

10. Fig. 10-25