I guess I’m behind the times, but I didn’t realize until this morning that the long-time nature blogger known as Bug Girl — who I even follow on Twitter, though obviously not closely enough — has come out from behind the pseudonymn (she’s Dr. Gwen Pearson), started a pretty cool-sounding consulting business aimed at helping nature centers and researchers get online, and best of all, has a blog at Wired called “Charismatic Minifauna.” The latest post is especially link-worthy:
The ability of a dragonfly nymph to successfully snatch and grab food is directly related to its anus. The mouth-grabber (labium) is hydraulically activated. The dragonfly draws water in through the anus, clenches, then compresses its abdominal and thoracic muscles against the water-filled rectal chamber. This raises the internal body cavity pressure, and pushes the labium out –in a strike that takes 10 to 30 milliseconds.
The amount of internal pressure generated is about 6000 Pa, or 6 kPa; equivalent to 0.87 psi (pounds per square inch). That doesn’t seem like a lot, until you consider that big nymphs only weigh 100mg (0.0002 lbs), so generating almost a pound of pressure WITH THEIR BUTT is pretty impressive. A Camaro turbocharger produces 7 psi, so you could say this little insect has 1/7th of a Camaro in its ass.
The other amazing function of a dragonfly nymph rectum is jet-propulsion. By un-clenching their rectum, water in the rectal chamber can be jetted out at high pressure, pushing the nymph forward through the water. The forward thrust generated is 1.5 g in 0.1 second; nymphs’ top speed is 10cm/second. They can throttle their rectum back to produce varying amounts of thrust through the water.
And there’s more. (Click through also for the link-references within the passage I quoted.)