( s the gut microbial flora said Marden...)Dragonfly's metabolic disease provides clues about human obesity

Another clue is that some AIDS patients, with compromised immune systems, have chronic problems with Cryptosporidium (a protozoan parasite closely related to the one found in dragonflies) that over time impairs their metabolism in a similar fashion to what Schilder and Marden found for infected dragonflies. "That information gave us the courage to connect the dots," said Marden. "Granted, it is a big extrapolation to think that our dragonfly results might have any relevance for human disease, but it would be irresponsible for us to not point out these possibilities. People who study metabolic disease should test the hypothesis that changes in gut microbial composition can cause these syndromes." __IMAGE_3

Marden's lab, which studies how insect muscles work and affect the animal's survival and reproductive capabilities, can mechanically isolate single flight muscles and measure their mechanical power output under conditions similar to those in nature. The researchers noted that the muscles of some dragonflies are able to perform at 80 watts per kg. while others of the same species could perform at up to 220 watts per kg. The life of a dragonfly and successful mating requires intense competition for pond territory, aerial contests, and high-performance flight. "These guys are the jet fighters of the insect world," said Marden. Flight muscle makes up 60 percent of their body mass. The large variation in muscle output was intriguing because natural selection, over time, would weed out the submissive, poor flyers if the trait were genetically based. When the researchers looked in the gut of the dragonflies with poor muscle output, they found parasites.

Healthy dragonflies can adjust their muscle performance according to how much fat they have available in their bodies, but the dragonflies infected with parasites weren't making that adjustment, Marden observed. He and Schilder began look
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Source:Penn State