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

Aposematic Disruptive Countershading Cryptic

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

Fishes - Biology Locomotion Bony fishes Surgeonfish Triggerfish 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

Fig. 10-21

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

Fishes - Biology Respiratory System Structure of Gills Gas Exchange 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