Transcript Carcharhinus leucas

There exists freshwater sharks which are
capable of surviving in fresh water lakes and
rivers. These sharks are;
1. The Bull Shark (Carcharhinus leucas).
This shark swims up tropical rivers around
the world.
2. The River Shark (Glyphis).
This shark is found in the fresh and brackish
water in Asia and Australia.
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The bull sharks are found along coastlines, bays,
and harbors. They also frequent freshwater
rivers.
This shark swims up tropical rivers around the
world (Heupel et al., 2010).
This shark is commonly found in the fresh
and brackish water in Asia and Australia.
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For most shark species, they are unable to survive in
fresh water because of the inhospitable surrounding
environment.
The shark would die due to a process called osmosis.
Osmosis occurs when a fluid moves through a semipermeable membrane from a solution with a low solute
concentration to a solution with a higher solute
concentration. This happens until there is an equal
concentration of liquid on both sides of the membrane
(Ballantyne & Robinson, 2010).
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Sharks evolved in salt water. They thus have very
salty bodies.
The sharks in fresh water contain more than twice
the amount of salt and chloride as more common
freshwater fishes.
Because of Osmosis, these sharks would burst like
an overfilled water balloon when placed in fresh
water.
However, these sharks have a special adaptation to
prevent this; they urinate a lot (Ballantyne &
Robinson, 2010).
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A study conducted on the Bull Sharks in Lake
Nicaragua revealed there is a lot of intake of
water by these sharks.
These sharks however excrete most of this
water as dilute urine.
Their rate of urination is about 20 times that of
the normal saltwater sharks.
These sharks' kidneys have adapted to utilizing
additional energy for this continuous excretion
process. This adaptation helps these sharks
survive in the freshwaters.
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Their ability of these sharks to tolerate
freshwater is rooted in salt retention.
Sharks must retain salt inside their bodies.
Without it, their cells will rupture and cause
bloating and death.
Given this requirement, most sharks cannot
enter fresh water. Their internal salt levels
would become diluted.
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To prevent this, the fresh water sharks have
special physiological adaptations that enable
them to live in fresh water.
Their kidneys recycle the salt within their
bodies and special glands. These special glands
are located near their tails, also aid in salt
retention (Ballantyne & Robinson, 2010).
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Yes. Fresh water sharks are endangered due to
environmental and human activities.
The population of the river shark is at dangerous
lows now.
Bull shark numbers are higher. The bull shark has
an advantage because it can navigate between
fresh- and saltwater environments.
The river sharks are more adapted to river and
lake life. They are thus almost prisoners within
their land-locked environments. These species
have thus got to withstand both natural and
human-induced problems.
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Natural problems
These include;
Temperature,
Oxygen,
Mineral content, and
Turbidity changes that continue to be
influenced by climate change..
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Human activities
These involve:
Dam building,
Modifications to water for irrigation and
fisheries, and
The introduction of pollutants into the water
(Gelsleichter, 2009).
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Plants grow better in fresh water
when compared to saltwater.
Saltwater is capable of damaging the
root system of the plant.
Too much salt is also capable of
interfering with the chemical process
and ultimately starving the plant.
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If you water a fresh water plant with salt water,
any moisture already in it will diffuse out and
into the soil. This is because the salt water has a
high solute content than the plant and will suck
all of the moisture out.
When exposed to salt water, the cells of the
fresh water plant lose water. The cell
membrane pulls away from the cell wall. This
is termed plasmolysis.
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The diffusion of water across a selectively
permeable cell membrane is termed osmosis.
The membrane is selectively permeable
because virtually none of the salt crosses the
membrane while the water passes freely across.
Plasmolysis results from this process of
osmosis which causes the cells to lose water to
the external salty environment hence resulting
in the cell membrane pulling away from the
cell wall (Pilizota & Shaevitz, 2013).
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Because of these dangers posed by excess
salt concentration in the water, the salt
water plants have unique physiology and
adaptations that allow them to survive in
this environments.
These physiological adaptations are what
prevent these plants from getting
dehydrated and dying (Pilizota, &
Shaevitz, 2013)
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The cell membrane of the freshwater plants
allows salt to enter the cell and accumulate in
the cell vacuole. This allows the cells to
accumulate a higher salt concentration than the
salt concentration in the salt water.
Thus, the cells of these salt water plants do not
plasmolyze. They are able to retain water
which helps these plants survive in these salty
environments.
Ballantyne, J. S., & Robinson, J. W. (2010). Freshwater elasmobranchs: a review
of their physiology and biochemistry. Journal of Comparative Physiology
B, 180(4), 475-493.
Gelsleichter, J. (2009). Project profile: Exposure Of Freshwater Sharks To
Human Pharmaceuticals. Evaluating the risks that pharmaceutical-related
pollutants pose to Caloosahatchee River wildlife: observations on the bull
shark, Carcharhinus leucas. Final Report: Charlotte Harbor National Estuary
Program.
Heupel, M. R., Yeiser, B. G., Collins, A. B., Ortega, L., & Simpfendorfer, C. A.
(2010). Long-term presence and movement patterns of juvenile bull sharks,
Carcharhinus leucas, in an estuarine river system. Marine and Freshwater
Research, 61(1), 1-10.
Pilizota, T., & Shaevitz, J. W. (2013). Plasmolysis and Cell Shape Depend on
Solute Outer-Membrane Permeability during Hyperosmotic Shock in< i> E.
coli</i>. Biophysical Journal, 104(12), 2733-2742.