I used to want to go inner-tubing on the Delaware. When we'd go canoeing, I'd watch all the lazy people in their swimsuits with their feet hanging in the water, their floaty coolers tied to their tube, their arms not cramped from endless paddling.
Not anymore. I recently saw two television shows that not only terrified me, but made me wonder, "How the heck haven't I heard about this before?"
There are SHARKS in the rivers.
Not just any shark, mind you. If, say, a Great White were to try to swim up a river, as soon as the fresh water infiltrated its skin, its cells would rupture and it would die. But the bull shark, which stands third on the list of shark species responsible for human attacks in Australia, has three unique adaptations that allow it to survive in fresh water. First, its skin has tiny receptors that measure the amount of salt in the water surrounding it. These receptors then communicate to a unique gland below its tail, capable of storing salt, and tell it to either purge salt or release it to the body. If this gland should happen to run out of salt, the shark's kidneys are capable of recycling and redistributing salt from its body.
Scared yet? Well, here's what I found out over the past few days.
-In Australia, bull sharks have been found several hundred miles upstream, even living in lakes. A man was killed in 2003 in Miami LAKE by a bull shark. A horse was also attacked in an entirely freshwater river. And on the show "River Monsters," the host found evidence, in the form of a juvenile shark, that they aren't just swimming into the rivers, they're BREEDING in them.
-Bull sharks have been sighted 2200 miles inland in Peru. Numerous attacks have been reported, by sharks ten feet long and greater.
-There have been several sightings of bull sharks in the Mississippi and Illinois rivers, including a shark attack in Lake Michigan, in which a man lost his leg. This happened in 1955, which makes me wonder...when was somebody going to tell me about this???
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