Fish Adaptations

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Fish Adaptations
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Why do I have to learn about fish?

• Fish are the most diverse group of vertebrates
  with 25,000 species
• Fish are weird and interesting
• Wildlife majorsthis may be
• your only class to learn
• about them

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Properties of Water

• Salt water covers 70 of the earth
• Fresh water covers 1
• 1/30 as much oxygen in water as in air
• 800 times denser than air
• 18 times as viscous as air
• High specific heat
• High electrical conductivity

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How does a fish breathe under water?

• Water flows in through mouth, out through gills
• Gills are structures to exchange CO2 and oxygen
• In gills, blood picks up oxygen from the
  surrounding water
• Blood goes to body, then back to heart to repeat
  cycle

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Gill is under a flap called the operculum
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Gill arch (gives gill support)
Gill raker (for trapping food)
Gill Filament (where gas exchange happens))
Heart
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Countercurrent O2 Exchange
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Obtaining OxygenGills

• Buccal pumping
• Water is pumped into mouth and
• out of operculum
• can be used when fish are at rest
• Ram ventilation
• Water is pushed over gills by swimming with mouth
  open
• fish must swim continuously

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Obtaining Oxygen--Skin

• Oxygen diffuses from water through the skin
• Used by larval fish of many species, and adults
  of a few species

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Obtaining OxygenBreathing Air

• Water does not provide enough oxygen for some
  fish
• Facultative air breathers
• Breath air only when necessary
• Obligate air breathers
• Must breath air or will die

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Obtaining OxygenBreathing Air

• Methods of breathing air
• Modified gills
• Walking catfish
• Mouth
• Electric eel
• Gut
• Some tropical catfishes
• Modified swim bladders
• Gars, bowfin
• Lungs
• lungfish

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Buoyancy

• Strategies to stay afloat
• Swimbladder
• Fat stored in the body
• Shape of fins
• Reduction of heavy tissues

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BuoyancySwim Bladders

• Overcomes inadequacies of other methods of
  staying afloat
• Fish adds gas to swim bladder when it swims down
• Removes gas when it swims up

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Physostomous fish (open swim bladder)

• phys bladder, stoma mouth
• gulp air at surface to fill bladder, burp to
  empty it

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Physoclistous fish (closed swim bladder)

• phys bladder
• clist closed
• regulate amount of air in bladder by secreting
  gas from blood through gas gland
• Fish free from going to surface all the time

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Thermoregulation (staying warm)

• Fish are ectothermic (cold-blooded)
• Must maintain certain body temperatures for
  metabolic functioning
• Behavioral thermoregulation
• Swim to different parts of the water column at
  different times of day
• Physiological thermoregulation
• Only a few warm-bodied fish species have this
• Still do not have constant body temperatures like
  mammals or birds

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Regulation of Ions and Body Fluids

• A fish can be
• Isotonichas the same concentration as
  surrounding water (Hagfishes)
• Hypotonichas a lower solute concentration than
  surrounding water
• Hypertonichas a higher solute concentration than
  surrounding water

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Sensory Systems

• Light only penetrates top portion of water column
• Water is often muddy
• Sound travels faster in water
• Fish need to detect predators, prey, mates as
  well as find their way around

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Vision

• Light only penetrates to 1000m in clear water
• Most fish see as well as
• humans
• Many see in color
• Lenses are perfectly spherical, to help them see
  underwater

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Taste

• Taste buds may be anywhere on body
  surfaceusually in mouth, on head, and on
  anterior fins
• Catfish have taste buds on barbels

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Smell

• Sharks and salmon can detect odors present in 1
  part per billion
• Salmon use smell to navigateget lost if their
  noses are plugged
• Fish can smell fear
• Pheromones

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Touch

• Water is incompressible (unlike air)
• Fish can detect water currents of 0.025 mm/sec
• Neuromast organs
• Clusters of hair cells
• Lateral line system
• Neuromasts organized in a series of lines on
  head, along sides of body and tail

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Hearing

• Sound travels 1433m/sec in water, only 335m/sec
  in air
• Most fish hear well
• No external earsinstead sound waves are received
  by tissue and other special structures (like
  human inner ear)
• Many species communicate audibly!
• Listen to this
• www.fishtalk

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Electroreception

• Water conducts electricity (especially salt
  water)
• Muscle contractions create electric currents in
  water
• More about this later when we discuss sharks

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Ampullae of Lorenzini
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Electrolocation

• Special sensory organs present in the skin of
  some fish that can emit weak electric charges
• Works like sonar
• Used to detect prey and find their way in murky
  water

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Locomotion

• Water is dense, so resists movement through it
• Ways fish lower the resistance
• Streamlined bodies
• High proportion of body devoted to muscle
• Efficient means of thrusting themselves forward

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How fish swim

• Two swimming types  
• . 
• Cruisers
• swim almost continuously in search for food
• tuna
• Burst Swimmers
• stay in a small area

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• Thrust
• Force in direction of movement
• Lift
• Force in right angle to thrust
• Drag
• Force opposite direction of movement

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Pressure drag
Frictional drag
Vortex drag
Fish shape and fish slime minimize drag
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Why does a fish need fins?

• To control body orientation
• Yaw (swinging back and forth)
• Pitch (tilting up and down)
• Roll (rotating around body axis)

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Fish Food

• Zooplankton
• Algae
• Smaller fish
• Large fish and mammals

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What is plankton?

• phytoplanktonmicroscopic plants and bacteria
• zooplanktonmicroscopic animals
• macrozooplanktonlarger fish eggs and larvae and
  pelagic invertebrates

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What is algae?

• Pond scum, seaweed, freshwater and marine
  phytoplankton, etc.
• Have chlorophyll (make their own food)
• Protista or plantae kingdom?

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Reproduction

• Who is whom?
• In most species, there are separate
• males and females
• Some species are born male, change to females
  later
• Others born female, change to male
• At least one species is all female

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Reproduction

• Egg scatters
• Nest Builders
• Egg depositors
• Mouth breeders
• Egg buriers
• Livebearers

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Vocabulary

• Buccal
• Obligate
• Facultative
• Gill
• Respiration
• Diffusion
• Countercurrent
• Neuromast organs
• Pheromones

• Physoclistous
• Physostomous
• Ectothermic
• Thermoregulate
• Isotonic
• Hypotonic
• Hypertonic
• Barbel
• Pelagic