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 • Reflective crystals in iridophores (specialized chromatophores)

• Functions1. Aposematic coloration

• Dangerous, poisonous, bad tasting

2. Cryptic coloration• Blend with environment – hide from predators, stalk prey

3. Disruptive coloration• Break up outline of individual fish – confuse predators

4. Obliterative countershading• Dark top, light bottom• Camouflage in open water

Aposematic

Cryptic Countershading

Disruptive

I. Fishes - Biology

C. 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)

1. Sharks• Lack swim bladder• Generate lift with

1) Buoyant oily liver

2) Heterocercal tail

2. Rays and skates• Generate lift with large pectoral fins• Narrow tail plays minor role in swimming

I. Fishes - Biology

C. Locomotion3. Bony fishes

• Swim bladder provides buoyancy• Diversity in swimming styles

1) Eel-like – Undulation of body• Ex: Moray eel2) Caudal – Propulsion with tail and body• Ex: Tuna3) Pectoral – Tail contributes little• Ex: Surgeonfish4) Dorsal/Anal – Tail used as rudder• Ex: Triggerfish5) Other• Ex: Trunkfish

Surgeonfish

Triggerfish

Fig. 10-21

I. Fishes - Biology

D. Respiratory System1. 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 System2. 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

3. Gas Exchange• Occurs by diffusion• Countercurrent exchange

• Increases efficiency of gas exchange

Fig. 10-23

Fig. 10-25