Transcript Living organisms

Estuaries
fresh & salt meet
Tremendously Productive
DETRITUS
Origin and Types
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Drowned river valleys or coastal plain estuaries
Bar-built estuary
Tectonic estuary
Fjords
Drowned or Coastal Plain
• 18K yr last ice age
• Chesapeake Bay, Delware and St Lawrence,
Thames
Bar-built Estuary
• Sand bars and barrier islands
• Barrier between ocean and river’s freshwater
• Texas coast, N. Carolina coast, N. Sea coast
Tetonic Estuaries
• Land subsided from crust’s movements
• San Francisco Bay
Fjords
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Cut by retreating glaciers
Steep wall
Alaska
Norway
Chile
New Zealand
Physical Characteristics
• Salinity: 35 ppt vs ~0 ppt
– Salt Wedge: bull sharks
– Tides offer wide fluctuations
• Substrate
– Sand to mud
– Mud rich in organic matter, anoxia
• Temperature
– Daily and seasonal
• Suspended sediments
– Feeding apparatus
Types of Communities
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Open water: anadromous and catadromous
Mud flats: infauna, meiofauna
Salt marshes: cord grass
Oyster reefs
Sea grass beds
Mangrove forest
The body
Diversity
Adaptations
Body Plans Provide Diversity
• A Question of Adaptation
• Often – Consumer and Consumed Co-Evolve
• Driver of Speciation – Exploitation of New Energy
Resources
• Topics on the diversity of fishes
– Anatomy
• Skin – keeps the body intact, etc.
• Jaws –respiration and feeding
• Appendages – locomotion and buoyancy
– Cardiovascular system
– Respiratory system
Energy Budgets
Intake ( I = Income)
• Macronutrients
– Carbohydrates
– Fats/Oils
– Proteins
• Micronutrients
– Vitamins
– Essential
• Fatty Acids
• Amino Acids
• Sugars
Energy Use (E = Expenditure)
• Respiration
• Osmoregulation
• Movement
• Feeding
• Digestion
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IF
I=E
I<E
I>E
Reproduction
Growth = 0
Growth =
Growth = +
Keystone System Circulatory system
Plausible Scenarios
• Ancestor chordates evolved in an isotonic setting
– All were marine since the start
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No osmotic gradients
No energy required for osmoregulation
Body surface was highly permeable
Some ion regulation
Kidneys were exclusively for excretion
When early vertebrates invaded freshwater
– Osmotic disruption resulting in excess water
• Absorption through thin epithelium
• Water intake from feeding
• Need to solve this problem along with ion balance
Osmosis is the tendency of water to move between two
solutions of different osmolarity separated by a barrier
permeable for water (e.g. membrane).
Living organisms
• an aqueous solution with solutes contained within a
series of membrane system
• volume [solutes] maintained within a narrow limits
for the optimal function
• deviations from physiological composition:
incompatible with life
• maintain the proper concentrations of body fluid
which invariably differ from the environment
• unlike cell walls of plants, the animal cellular
plasma membrane is not equipped to deal with high
pressure differences or large volume changes
Where are the regulated areas?
• Intracellular osmoregulation is the active
regulation that guarantees the absence of pressure
gradients across plasma membranes, aka cell
volume regulation
• Extracellular osmoregulation is the active,
homeostatic regulation that maintains the osmotic
concentrations in the body fluids, even if the
environmental osmotic concentration changed.
• Mainly water and NaCl are maintained
Osmoregulation: ability to hold
constant total electrolyte and
water content of the cells.
Critical for survival and success
Concepts of osmorality
• Osmotic concentration of a solution can be
expressed as osmorality (osmoles per liter)
• Concentration of a dissolved substance is
expressed in units of molarity (number of
moles per liter solution)
• Osmorality of a nonelectrolyte (sucrose) equals
the molar concentration: 1M = 1 Osm per liter
• Osmorality of an electrolyte (NaCl) has a “higher”
osmorality because of ionic dissociation and hence
exerts a “higher” osmotic force
– Not exactly because concentration and the interactions
between ionic charges with water can influence the
system
– Along with the low osmotic coefficient of NaCl (Φ =
0.91)
• Osmotic concentration determined by
– measuring freezing point depression
– vapor pressure of the solution
– Seawater osmotic concentration: 1000 mOsm
• 470 mmol Na & 550 mmol Cl
Two categories of osmotic exchange
Obligatory
has little control such as trans-epithelial diffusion,
ingestion, defecation, metabolic water production
Regulated
physiologically controlled and help maintain
homeostasis (active transport)
Two Strategies to minimize this problem
• Decrease the concentration gradient
between animal to environment
• Lower the permeability to the outside in
areas that are compromised (gills, gut)
Even so
• Always some diffusive leaks
• For a counter-flow system to equal this leak
– needs energy
– Osmoregulators spend 5% to 30% of their metabolism in
maintaining osmotic balance
• Highly variable aquatic environment
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Freshwater
Brackish water
Seawater
Hypersaline water (Med )
Soft water runoffs
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Euryhaline:
Stenohaline:
isomotic:
osmoconformer:
osmoregulator:
Four groups of regulation dealing
with water in fishes
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Hagfish
Marine elasmobranchs
Marine teleosts
Freshwater teleosts and elasmobranchs
Five groups of regulation dealing
with ions in fishes
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Hagfish
Marine elasmobranchs
Marine teleosts and lampreys
Freshwater teleosts
Euryhaline and diadromous teleosts
Aganthans
• Lampreys live in sea and freshwater but
hagfish are strictly marine
• Both employ different solution to life in the
sea
Hagfish
• Are the only true vertebrates whose body
fluids have salt concentration similar to
seawater
• Have pronounced ionic regulation
Lamprey
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Egg & larvae develop in fresh water
Some species stay, some migrate to sea
Adults return to breed (anadromous fish)
Osmotic concentration about 1/4 to 1/3 of
the seawater
• Face similar problems to that of the teleosts
Marine Elasmobranchs & Holocephalans
• [Salt] at about 1/3 of seawater
• Osmotic equilibrium achieved by the
addition of large amount of organic
compounds
– primarily urea (0.4M)
– various methylamine substances
• 2 urea :1 TMAO
• trimethylamine (TMAO), sarcosine, betaine, etc.
• Blood osmotic concentration slightly
greater than seawater
• Water is taken up across the gills, which is
used to remove excess urea via urine
formation
• Small osmotic load for the gills
• Urea and TMAO are efficiently reabsorbed
by the kidneys
But
• Urea disrupts, denatured, cause conformational
changes in proteins, collagen, hemoglobin, and
many enzymes
• Some elasmobranch proteins are resistance to urea
• Yancey & Somero (1979):
– Proteins are actually protected by the presence of
TMAO
– found to have a consistent ratio of 2 urea to 1 TMAO
(also in Holocephalan and Latimeria)
Neat invention
• Strategy of using waste products as an
economical way for osmoregulation; unlike
the invertebrates which invest on free amino
acids to increase serum osmorality
• ionic composition is different from seawater,
hence still need to spend energy for ionic
regulation
• Need to have the ornithine-urea cycle
Freshwater elasmobranchs
• sawfish, bull shark (C. leucas), stingrays are
euryhaline
– live in brackish and even freshwater for long
time (Bull in Lake Nicaragua, Mississippi
rivers)
• Urea (25-35%), sodium, and chloride are
reduced as compared to sw counterparts
• produce copious flow of dilute urine to deal
with the water influx
• In freshwater rays, they abandoned urea
retention, and reduced ionic content to cope
with this problem
• These freshwater rays are not able to make
urea when presented in seawater
Coelacanth
• Blood composition is similar to the marine
elasmobranchs
• Total osmorality is less than seawater
• This maybe due to the habitats they live in:
aquifers feeding into the caves and fissures
that could presumably lower salinity: hence
a localized hyperosmotic to the
surrounding????
Teleost Fish
• Maintain osmotic concentration at about 1/4 to 1/3
of seawater
• Marine teleosts have a somewhat higher blood
osmotic concentration
• Some teleosts can tolerate wide range of salinities
• Some move between fresh and salt water and are
associated with life cycle (salmon, eel, lamprey,
etc)
Marine teleosts
• Hyposmotic, constant danger of losing water to
surrounding via the gill surfaces
• Compensate for water loss by drinking
• Salts are ingested in the process of drinking
• Gain water by excreting salt in higher
concentration along the length of its convoluted
tubules
• Produce small amount but very concentrated urine
– 2.5 ml/kg body mass/day
• Kidney cannot produce urine that is more
concentrated than the blood
• Need special organ, the gills
• Active transport requires energy
• Water loss from gill membrane and urine
• Fish drink to balance the water deficits
• Na and Cl secreted via the gill’s chloride cells
• Gut: for elimination of divalent salts