Locomotion

Aquatic Locomotion

Earliest form of locomotion in vertebrates

Aquatic Locomotion- Forces to generated & reduce/counteract what?

• Two forces to be generated:

– Lift: counteracts effects of gravity (vertical plane)

– Thrust: forward/backward motion (horizontal plane)

• Must also reduce drag (resistance)

• And counteract instability

Providing Lift

• Swim Bladder

– Fish regulate amount of air inside body

(via gases in blood, or through connections to

esophagus)

– Increasing/decreasing buoyancy

• Low density body structures

– Density of organs less than water

thanks to oil storage

(e.g., oily flesh, liver, etc.)

– Provides buoyancy

• Fins

– Heterocercal caudal fin particularly

good at generating lift in addition to thrust.

Providing Thrust

– Swimming locomotion done by undulations (waves), or oscillations (back-and-forth)

– Thrust is typically created by caudal region, but other regions also utilized (e.g., pectoral or anal fins)

Swimming Types can be classified according to ?

body regions used, and type of movement

Undulation

waves motion

Oscillation 

back and fourth motion

Thrust/Swimming: Movement Types

Anguilliform, Carangiform, Ostraciiform, Appendicular Locomotion

Instability

Rotation about the three axes

Instability- Roll

along longitudinal axis, tendency to move side to side

– Controlled by dorsal and anal fins

Instability- Pitch

along transverse axis, up & down movement, esp. at the front of the bodythe

– Controlled by pectoral fins; pelvic fins in

advanced fish

Instability- Yaw

along sagittal axis, tendency to go right or left

– Controlled by fins at back with vertical orientation, e.g. caudal fin

Counteracting Instability

Counteracted by fins:

1. Pitch (pectoral fin, pelvic fin)

2. Roll (dorsal fin, anal fin)

3. Yaw (tail fin (caudal fin))

Drag

Force that counteracts thrust

Causes of Drag

– Friction between body and water (viscous drag)

– Turbulence as fish moves and displaces water (inertial drag)

Reducing Drag

• Body Covering:

– smooth skin reduces viscous drag (no scales or many small ones)

– mucous/slime over scales reduces viscous drag by as much as 60%

• Body Shape: streamlined body reduces inertial drag, thin body = more viscous drag, but less turbulence

Fish Speeds

• Anguilliform: bursts 2-3 body lengths/second (bl/sec)

• Carangiform: bursts 10 bl/sec

Fish Muscle Types

• White: up to 90% of muscle

– Few mitochondria, poorer blood supply

– Good for bursts, but fatigue quickly

• Red: endurance, little force

– More mitochondria, good blood supply

– Used for cruising; show little fatigue

Anguilliform Swimming

Most of body used to produce thrust

• Muscles contract on one side,

relax on other; wave of contractions

• Examples: eels, shark (dogfish)

Carangiform Swimming

Front half body rigid, back half produces waves and contractions

• Examples: jack, trout, horse mackerel

Ostraciiform

Only caudal fin involved in thrust (wig-wag motion)

• Example: boxfish (trunkfish)

4) Appendicular Swimming

Use appendages for swimming

• Undulatory:use fin undulations

  • Dorsal and/or anal fins: e.g., bowfin, knife-fish

  • Pectoral fins:e.g., rays, skates, pufferfish

• Oscillatory: use back / forth movement of appendages

  – Use limbs like oars — frog, duck, otter

  – Use fins like wings — turtle, penguin, seal