MadSci Network: Zoology

Re: Can we develop a freshwater octopus as tought as a turtle?

Date: Tue Feb 1 01:31:29 2011
Posted By: dave armstrong, Faculty, Biology, Cedars Tutoring, Qatar
Area of science: Zoology
ID: 1295334394.Zo

Dear Tiago,
		Your river turtle was very lucky to survive but unlike sea turtles, it
was adapted to a changeable water content (its concentration or dilution).
The sea was the source of all of our distant ancestors because it has
stable chemistry. The concentration of most substances in the marine
environment varies only with depth. Most organisms live within 10 metres of
the surface, so the environment is so stable that it’s a wonder anything
gave up such a safe place to live! The water also supports their
bodies.Land animals and probably freshwater animals before them adapted to
terrible ”drought” and awesome “flooding” respectively. Their bodies are
forever robbed of all water on land and flooded with dilute water in most
rivers and lakes.
	Now you have a problem. As a water animal, the turtle has both the ability
to control its water content and a tough outer carapace to help with
exposure problems. You may say the octopus is adapted, but never to the
freshwater environment. His ancestors only lived among the rocks of the
sea. No genetic engineering could provide him with the osmotic control to
lose excess water in a river or prevent water loss  on land. The ancestral
coiled shell, typically Mollusc, could only help if some method of movement
could evolve for land . In effect, your proposal hits on two obvious rebuttals—
	[1] mutable characteristics in the octopus such as a reversion to its
shelled ancestral type (such as the Pearly Nautilus)could not provide any
useful adapation to life on land or in rivers
	[2] genetic modification of a species is possible only within specified
narrow limits. You have to change the genes that are present or introduce
one that you know will perform a simple change.
	The future holds incredible ideas that will change our comprehension of
life. I doubt if we can see the octopus changing its behaviour and its muscles.

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