New Scientist reports that the Cronulla Fisheries Centre in New South Wales has a new plan to save the endangered Grey Nurse Shark.

Grey Nurse Sharks start with around 40 embryos per pregnancy. However, the embryos have a tendency to eat each other in the womb, meaning that only a couple make it to term.

CFC is building a series of the artificial uterus' so that each embryo can be removed from the mother and brought to term. "No eating your brothers and sisters now!"

Ok.. this sounds like a good plan on the face of it - except for a couple of things. An artificial uterus? Pregnancies are hard to pull off even using the original equipment, so it will be interesting to see how successful an artificial womb is.

But aside from that, nature rarely does things without reason. Not mindful reason of course, but billions of years of trial and error reason. Forty embryos are fertilised each with the capability of coming to term, so what is the evolutionary benefit of wasting this energy in a cannibalistic feeding frenzy?

Nutrition? Why convert energy into an embryonic shark only to then use it as a food source? Efficiencies are lost in this process.

Many animals "stress test" embryos for suitability before allowing them coming to term. Even in humans, as many as one in three embryos don't make it. It would seem that the most likely explains what is happening is that the world that these sharks will be entering is a harsh one, particularly when they are young, and this process helps weed out all but the strongest of the pups to be - those with that have the greatest edge.

So while interfering with this process may increase the number of sharks born, surely the quality will be diminished.

These sharks are near extinct, so while the idea of bringing as many into the world as possible would seem a good strategy, the consequences of releasing so many sharks that would not normally be brought into the world could have long term detrimental effects - the gene pool quality is reduced and this would surely have an impact on the long term survivability of the species.



Tuesday, August 5, 2008

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