I Fishes Biology B Coloration Pigments in chromatophores
I. Fishes - Biology B. 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 • • 1. Reflective crystals in iridophores (specialized chromatophores) Functions Aposematic coloration • 2. Dangerous, poisonous, bad tasting Cryptic coloration • 3. Blend with environment – hide from predators, stalk prey Disruptive coloration • 4. Break up outline of individual fish – confuse predators Obliterative countershading • • Dark top, light bottom Camouflage in open water
Aposematic Disruptive Cryptic 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 Rays and skates • • Generate lift with large pectoral fins Narrow tail plays minor role in swimming
I. Fishes - Biology C. Locomotion 3. Surgeonfish 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 Triggerfish
Fig. 10 -21
I. Fishes - Biology D. Respiratory System 1. Irrigation of Gills a. • 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 b. Actinopterygii/Osteichthyes • Gills housed in common gill chamber • Openings covered by operculum on each side • Mouth opens/operculum closes & vice-versa
I. Fishes - Biology D. 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
Fig. 10 -23
Fig. 10 -25
- Slides: 10