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It’s Weird Gramma again, and this is “WeirdFins,” all about strange stuff in the sea, and brought to you by the National Oceanic and Atmospheric Administration. This time, it’s about baby shark cannibals that eat their brothers and sisters before any of them are even born!
Yep, it’s true, and the shark we’re talking about is the sand tiger. Now, after sharks mate, some lay eggs that hatch out later. But most kinds bear their young live, and in some, like great white sharks and makos, the pups develop inside the mother, in a soft bag called an eggcase. They’re nourished in there by egg yolk, but after the yolk’s all used up, they still stay inside the mother and eat the unfertilized eggs, the ones that didn’t develop. So when they’re finally born, these babies are pretty big, and that does a lot to discourage hungry predators. White sharks are about 5 feet long when they’re born, almost as long as your bed! Think about that when you put on your pj’s tonight!
But with sand tigers, the developing pups don’t just eat the egg yolk. The first one or two pups that hatch from the soft eggcases gobble up their all their unhatched brothers and sisters, so they get nice and big, too, almost 3 feet long!
Now, even though they’re huge, each mother sand tiger bears only one or two pups every year, and they grow real slow, so there’s never been a whole lot of sand tiger sharks. And now, fishing and pollution have reduced their number to dangerously low levels. Like all sharks, sand tigers are real important to healthy oceans, so we need to protect and conserve them.
Check out all the NOAA Web sites that are loaded with interesting stuff on sand tigers and other sharks. And you can see pictures of sand tiger sharks on the National Marine Fisheries Service WeirdFins link at www.nmfs.noaa.gov.