Characteristics of Water ContinuedImplications for fish biology

end

2006

Many other substances ionize in water:

Salts: NaCl Na+ Cl-+

Bases: NH3 + H2O NH4+ OH-+

Acids: H2CO3 H+ HCO3-+

carbonic acid

ammonia

bicarbonate

ammonium

end

Density of water

H HO

OHH

OHH

H HO

HHO

Ice: voids

voids

voids.

Covalent bond-share electrons Hydrogen bond-electrostaticend

As temp of ice increases:

• Molecules vibrate more rapidly

• hydrogen bonds begin to break

• free molecules fill voids

• water becomes densest

• vibrations increase in amplitude; intermolecular distances increase

TEMP.

0 °C

3.94 °C

100 °C

Densityg/ml

Ice 0.917water 0.9999

1.000

0.996

Significance with respect to life?end

Thermal Stratification:

epilimnion

hypolimnion

thermocline

less dense

more dense

end

end

Density of water increases slightly with salinity

Salinity 0/00

Den

sity

%

0 35100

102.9

(sea water)

end

Viscosity:

• Viscosity - tendency for a fluid to resist motion within itself due to attraction among molecules.

• Salinity - little effect on viscosity (slight inc)

Characteristics of water continued:

end

Comparative Viscosities:

Substance Viscosity kg/m/s

acetone 0.326 x 10 -3

freshwater 1.002 x 10 –3 20 C

saltwater 34.8 g/l 1.072 x 10 –3 20 C

mercury 1.554 x 10 -3

glycerin 1.490

end

Temperature vs Viscosity

Temperature C

Vis

cosi

ty 1

0-3 k

g/m

/s

Viscosity doubles as temp. decreases from 25 to 0 C/

Viscosity of water offers approx. 100 x the resistance to movement as air.

0

0.5

1

1.5

2

0 10 20 30 40 50

end

end

Surface Tension

• Defn--inward adhesion of molecules at surface due to attraction of molecules

• surface tension of water is higher than any other liquid except mercury

• increases slightly with salinity

• decreases with temp

end

spider jumping

end

water striderend

end

Specific heat

• Defn--amount of energy (in calories) required to raise temperature of 1 g of substance 1 degree C

• water is standard with value of 1 (varies with temp but close to 1)

end

Comparison of specific heat

Substance Specific heatcopper 0.09rocks 0.2

ice 0.5water (distilled) 1.0liquid ammonia 1.23liquid hydrogen 3.4

end

end

Effects of Properties of Water on Living Organisms

Density & Buoyancy

Archimede’s Principle--when an object is immersed in a fluid, an upward force acts on it, equal to the weight of the fluid it displaces

end

air

waterneutral

buoyancy

positive buoyancy positive

buoyancy

negative buoyancy

positivebuoyancy

= H2O

> H2O

=

==

Archimedes Principle

neutral buoyancy

Fish?

end

Densities of Biological Substances:

Substance Density g/cm3

lipids 0.9freshwater (20 C) 1.002saltwater (20 C) 1.072

muscle 1.05bone (dry) 1.1

silaceous cell walls 2.0cellulose 1.5

calcium carbonate 3.0

end

Slight negative buoyancy--densities of most aquatic organisms are close to that of water (usually slightly more dense)

fish densities--1.06-1.09 g/cm3

end

Support

Aquatic organisms are well supported due to density similarities between water and aquatic organisms

Effects--reduced energy expenditure

reduction or lack of support tissues

end

Streamlined shapes

• Active fish tend to be streamlined due to high energy required for locomotion in water

end

Ecological Groups of Fishes

Six general categories

body shape

habitat

general life style

Clues to lifestyle

Doesn’t fit all fishes

1. Rover predators

2. Lie-in-wait predators

3. Surface oriented fishes

4. Bottom fishes

5. Deep-bodied fishes

6. Eel-like fishes

http://www.und.nodak.edu/instruct/skelsch/425~1.htm

end

1. Rover Predators--moving hunters

• Terminal mouth

• Fins evenly placed (maneuverability)

• stream-linedbrassy minnow

end

Ex: Salmonidae

brook trout

end

Ex: Percidae

walleye

end

Ex: Centrarchidae (basses only)

largemouth bass

end

2. Lie-in-Wait predator (piscivores)

• Terminal mouth; large w needle-like teeth

• Stream-lined; often elongated and thin

• Head flattenednorthern pike

end

Lie-in-Wait predator (continued)

• Caudal fin large

• Dorsal and anal fins placed posteriorly

• Cryptic coloration

end

Esocidae-pikes, pickerel, muskie

muskellunge

end

Lepisosteidae - gars

longnose gar

end

needlefish

end

Sphraenidae -- barracuda

longnose gar

end

3. Surface-Oriented fishes

• Often small

• Upward tending mouth (superior or superterminal)

• Dorsoventrally flattened head

• Adapted to surface life

Poeciliidae-live bearersguppies

mollies

Gambusiamosquitofishend

Four-eyed fish

end

Cyprinodontidae-pupfish, killifish

banded killifish

end

• betas

• archerfish

Other surface oriented fishes

Gambusia

end

4. Bottom fishes (benthic)

• Swimbladder reduced or absent

• flattened dorsoventrally (depressed)

Atlantic halibutend

Bottom fishes continued

• Specialized structures:

sensory structures barbels, fin rays

modified fins (darters, clingfishes)

barbels

end

sea robin

sea robin

end

• flounders

• soles

• tonguefish

Pleuronectiformes-flatfishes

end

hog choker

end

Acipenseridae--sturgeons

lake sturgeon

end

Skates & rays

end

5. Deep-bodied fishes Laterally flattened (compressed)

• Dorsal and anal fins long

• Pectoral fins high on body

• Pelvic fins thoracic

• Mouth protrusible

• Fin spines

French angelfish

lookdown

butterfly fish

maneuverability

end

Centrarchidae-crappies & sunfishes

bluegillend

6. Eel-like fishes--elongated bodies

• Paired fins reduced or absent

• Dorsal and anal fins long

• Scales small or absent

• Flexible bodies

• Adapted for small crevices

end

American eel

slime eel

snake eel

end

moray eel

end