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Zebra fish points to the importance of saving species

Friday, January 2, 2004

Know someone with a damaged heart? Ever heard of a zebra fish? Want to know the connection? While a broken heart often fixes itself over time, no human as far as we know can physically re-grow a heart. But apparently a zebra fish can.

In an article in Science magazine, researchers reported cutting out 20 percent of a zebra fish's heart. Immediately, the fish's heart started to clot. Within a short time, heart muscle cells began to show up around the wound, eventually replacing the excised portion.

Since all life is blueprinted by the DNA within it, researchers are hopeful that someday they'll be able to understand the genetic underpinnings of the zebra fish's remarkable ability to regrow its own heart. And apply that knowledge to damaged human hearts.

A good reason to take care of living things on the planet. You never know when one might contain instructions for fixing something wrong with us.

Speaking of living things on the planet, ever wonder how many different kinds there are? Edward O. Wilson, Pulitzer-winning author, entomologist, and a guy a lot of people consider to be the father of conservation biology, wanted to know much the same thing. So he spent 10 years, studied up, then wrote a marvelous book -- "The Diversity of Life." Among other things, the book attempts to answer that question.

Wilson estimates the number of plant and animal species living on earth to be between 10 and 13 million. Here's more on those numbers.

Scientists believe that about 98 percent of the living bird species are known. In contrast, less than 1.5 percent of algae species are known.

About one-third of all species are parasites. Next time someone overstays their visit to your house, remember they're just part of the natural order of things.

Although an exact number is unknown, bacteria, which have DNA, probably outnumber all living things. A pinch of soil between your fingers contains as many as a million different kinds of bacteria. Most unknown.

Wilson estimates that roughly 13,000 new species are discovered every year. This is not the same as new species popping into existence.

Wilson waded through roomfuls of scientific studies to come up with a rate of species extinction. He believes between 1 and 10 percent of all species disappear each year. That would be between 100,000 to 1.3 million species disappearing every year. Why should we care about any of this? Don't species go extinct all the time? Geologically speaking, yes. Scientists estimate that during the last great die-off some 65 million years, about 98 percent of all species kicked the bucket. Scientists also estimate that it took about 10 million years for species to recover and repopulate the planet.

The big problem is, if humans reduce the habitat for species over the course of decades, as opposed to millions of years, the diversity of species during our lifetimes will plummet.

Many scientists believe that the three biggest reasons for species extinctions are loss of habitat, pollution and invasive species. An ecological rule of thumb for loss of species related to loss of habitat is this: A loss of 90 percent of a habitat results in about a 50-percent loss of species.

Species loss also happens in the water. Which brings us back to the zebra fish.

As we unlock the genome, the genetic code connecting all life together, we see that nature experiments with many different strategies for survival. These are scattered among millions of species. If we lose species, we lose pieces of code. Instructions we may someday wish we hadn't carelessly thrown out.

The ability of the zebra fish to repair its heart should perhaps give us pause. To look inside our hearts. And see what we can do to protect the diversity of life that shares the planet with us.

Phil Helfrich is a community outreach specialist with the Missouri Department of Conservation.


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