17 September 2005

Wildlife pictures - Drosophila

There are very, very few organisms with scientific names familiar to the general public. So I was actually pretty psyched to find that Drosophila is familiar enough that it's in the spell checker dictionary. There's a reason for that, of course, and it doesn't have anything to do with wildlife. Drosophila melanogaster is the "fruit fly" that's been used in thousands of laboratory experiments over the years. Lots of people have gotten to see them in high school or college labs, crawling around in little tubes with food in the bottom.

D. melanogaster may be the popular member of the genus, but it's got a lot of company. This single genus contains an enormous number of species - well over 1000 have been described to date, and there are hundreds of species that have been collected but not yet described. There are species of Drosophila known from all over the world.

Many of them are native to Hawaii. Millions of years ago, a single species of Drosophila arrived in the Hawaiian Islands. The population that arrived was very small, perhaps as small as a single fertilized female. From that small start, an amazingly diverse fauna has evolved. Hundreds of species have been described to date, hundreds more have been collected but not yet formally described, and there is now way to know if we have discovered all of them yet.

The pictures show two of the species from one of the better-known groups of native Hawaiian Drosophila - the "picture-winged" group. These flies are giants among Drosophila - almost as large as house flies. The two flies pictured here are both about the same size, and the picture on the bottom has the edge of a quarter for scale.

The top picture is Drosophila silvestris, and the photo on the bottom is Drosophila heteroneura. Both are endemic to the island of Hawai'i (the Big Island), and both are usually found living in the same locations. They are closely related species, and can hybridize in the lab, where they yield fertile and vigorous offspring. In nature, however, they do not appear to interbreed.

Both pictures were taken with a 4MP Cannon digital camera, shooting through a binocular microscope at 6.3x.
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