Download Respiration

Rank in order of fastest to slowest
A
B
C
What type of caudal fin does this fish
have?
What is the body form of this fish?
What are the structures to which the
arrows point?
What type(s) of scales is these ain’t?
Barrel eye
Angler Fish
Structure of Fish Gills
Countercurrent exchange
• Countercurrent “multiplier system”.
• Occurs when:
– Transport of substance (e.g., O2) is by
diffusion.
– Two fluids flow in opposite directions in close
proximity.
• One of the most important of all
adaptations for efficient diffusion.
– In gills, allows for as much as 90% of O2 in the
water to diffuse into the blood.
• Found in many places throughout the
vertebrate body where gases, salts, or
heat are concentrated.
Source: http://www.geocities.com/aquarium_fish/how_fish_breathe.htm
Gills and
Countercurrent
Exchange of Gases
Direction of water flow is
counter that of blood flow in
capillaries.
Countercurrent exchange of gases across the
gill epithelia (on gill lamellae)
• Critical tradeoff for aquatic organisms:
– Large surface areas are necessary for
oxygen exchange.
– Exposes individual to:
• Other dissolved compounds in water, including
toxic compounds.
• Salinity and temperature fluctuations.
Gill Dimensions and Life Style in
Teleost Fishes
Gills are controlled by muscles
• Any water that passes by gills without
coming into close contact with blood
represents wasted energy.
• But gills must sometimes be flushed.
• Adductor and abductor muscles control
the positions of gill filaments.
Air-breathing fishes
• Hundreds of convergent cases of air-breathing using
accessory structures.
– Most are facultative air-breathers.
– Some are obligatory: drown if kept from the surface.
• Adaptations to two ecological conditions:
– Depletion of oxygen in the water.
– Periodic droughts.
• Most species are tropical freshwater or estuarine.
– Oxygen-deficient water more common in tropics.
•
•
•
•
Much decaying organic matter in water, consumes O2.
High temperature increases bacterial action.
Shaded jungle waters support little photosynthesis.
Little temperature variation supporting thermal
convection.
Gas bladder
• Gas-filled sac:
– Forms as diverticulum from anterior gut.
– Pressure regulated by countercurrent exchange
system (gas gland, =rete mirabile, =rete).
• Connection to gut may be present or absent.
– Physostomous vs. physoclistous (=physocleistous)
• Functions:
– Original function:
• Respiration: in lungfishes and many primitive
bony fishes.
– Derived functions:
• Buoyancy.
• Resonator: for producing or detecting sounds.
Connections of
gas bladder
with gut
Teleosts
Gars, bowfin
Bichir
Lungfishes
Amphibians
Teleosts
Tetrapods
Osteichthyes
Sarcopterygians
Homologies of respiratory systems
• Gills and lungs are not homologous:
– Developmental patterns very different.
• Anterior vs. posterior pharynx.
– Some species have both.
• Lungfishes, early amphibians.
• Lungs of tetrapods are homologous with gas
bladders of fishes:
– First observed in early placoderms (jawed
fishes).
– Derived function in modern fishes:
buoyancy.
Solubility of Oxygen in Water
Solubility of oxygen in water is affected by:
temperature
salinity
Freshwater in equilibrium with the atmosphere
contains 1/23 the oxygen concentration, per
unit volume, as does the atmosphere at 5oC.
1/43 at 35oC.
Solubility of Oxygen in Water
At 35oC the oxygen concentration, at
equilibrium, is 6.94 mg/l (ppm).
At 5oC the oxygen concentration is 12.76 mg/l.
Normoxic (normal oxygen) conditions are those
at or near saturation, that is near 156-mm HG
partial pressure of oxygen (PO2).
Dalton’s Law of Partial Pressures
The partial pressure of an ideal gas in a
mixture is equal to the pressure that gas
would exert if it occupied the same volume
alone at the same temperature.
A consequence of this is that the total
pressure of a mixture of ideal gases is equal to
the sum of the partial pressures of the
individual gases.
Dalton’s Law of Partial Pressures
For example, given an ideal gas mixture of
oxygen (O2), carbon dioxide (CO2) and ammonia
(NH3):
P = PO2 + PCO2 + PNH3
Relationship of PO2 and O2 Content.
Fish Respiration Summary
Water severely limits the solubility
(availability) of oxygen, yet fishes have
numerous adaptations that allow them to
survive in virtually all aquatic (and some
terrestrial) habitats.
Oxygen requirements vary among species, and
with life history stage, size, and activity level.
Oxygen requirements vary with temperature.
Hematological Characteristics
of Fishes
Hematological Characteristics
of Fishes
Fish Hemoglobin
Fish hemoglobin of is two basic types:
monomeric and tetrameric.
Monomeric- single-heme polypeptide
molecules with a molecular weight of about
17,000 daltons.
Characteristic of lampreys and hagfish
Lamprey and
Hagfish
Lamprey (attached
to lake trout)
Hagfish
Tetrameric Hemoglobin
Characteristic of all fishes except lampreys
and hagfish. Composed of four amino acid
chains (two a and two b chains) and have a
weight of approximately 65,000 daltons.
Within species, hemoglobin may be
polymorphic:
Four kinds of hemoglobin found in rainbow
trout, two in American eels.
Tetrameric Hemoglobin Molecules
Ecological Significance of
Hemoglobin Polymorphisms
In catadromous American eels, one hemoglobin
has a high affinity for oxygen in saltwater
conditions and one with high affinity for
oxygen in freshwater conditions.
The desert sucker possesses a pH-insensitive
hemoglobin that maintains a high oxygen
affinity when binding efficiencies of other
hemoglobins are reduced in the presence of
elevated plasma lactic acid concentrations due
to muscular activity.
American Eel
Desert Sucker
Hemoglobin Polymorphisms
Changes in hemoglobin types have been
observed in Coho salmon. Changes occur with
the progression from fry to presmolt stages.
Presence of multiple hemoglobins may negatively
affect performance. In turbot (Scophthalmus
maximus), individuals with two hemoglobin types
grow more slowly than those with a single
hemoglobin (one of which has relatively low and
the other relatively high oxygen affinity).
Turbot
Oxygen Affinity of Hemoglobin
• Oxygen molecules bind reversibly
to hemoglobin:
Hb + O2
HbO2
– High oxygen concentration in blood:
• Hemoglobin (Hb) combines with oxygen to
form oxyhemoglobin (HbO2).
– Low oxygen concentration in blood:
• Oxyhemoglobin dissociates to hemoglobin +
oxygen.
Bohr Effect and Root Effect
Capacity
Affinity
Blood Oxygen Saturation
Curves
Blood Oxygen Saturation
Curves
Oxygen Affinity of Hemoglobin
• Relationship between O2 concentration and PO2
saturation depicted by an oxygen dissociation
curve:
Max binding
capacity
Shift to right
indicates
decreasing
binding affinity
• Curves can differ dramatically for different
species and different environments.
Oxygen Dissociation Curves
Trout: cool, highly
oxygenated water
Eels: warm, moderately
oxygenated water
Oxygen Affinity of Hemoglobin
• Factors affecting O2 binding:
– pH:
• Decreasing pH (acidity) shifts curve
to right (Bohr effect).
• Effect is greater in fishes than
mammals.
– Temperature:
• Increasing temperature weakens bond,
shifts curve to right.
• Beneficial: temperature increase
causes increased metabolic rate.
• Counteracted by decreasing solubility
of O2.
– CO2:
• Increasing CO2 lowers pH, shifts curve
to right.
• Beneficial: high CO2 concentration
causes more O2 to be given up to body
tissues (Bohr effect, Root effect).