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More from _Insect Diets_

I'm currently reading the chapter on insect feeding and digestion.

Here's the thing: insects are tremendously diverse. They are one of the most diverse groups of organisms on our planet, and that's a big part of why a lot of people think we need to do a good job of cataloguing them (to say nothing of preventing species from going extinct).

It naturally follows that insects have diverse, amazing feeding apparatuses and digestive systems. I'll just highlight two.

First example: mosquitoes. People like to refer to mozzies as "flying syringes," because they don't simply poke you and then lap up blood as it comes out. No: they inject anticoagulants, and THEN they take out blood.

Then there are xylem-feeding insects, which extract liquid from a fluid-filled plant tube that operates with negative pressure (in contrast, blood flows via positive pressure). To suck out the liquid, these insects have to have a strong, muscular pump inside a region of their head called the cibarium. Scientists think the need to fight against negative pressure explains why there aren't any small xylem-feeding insects: those insects wouldn't have adequately large cibaria to counteract the xylem's negative pressure.

Yeah, crickets are pretty boring in comparison.

There are also lots of exotic modifications to the digestive tract, depending on whether the organism is trying to extract nutrients from an extremely nutrient-poor aqueous solution, like the xylem-feeder, or from a slurry, et cetera. The insects that feed on extremely nutrient-poor liquid solutions tend to have incredibly long and convoluted digestive systems that promote swift removal of water and excess nutrients. Mosquitoes, for example, pee out extra liquid while they feed (starting at 2:02). Again, way more exotic than standard mammal examples.

The thing I really hadn't thought about much is this: digestive enzymes are very effective, but don't necessarily discriminate between the lining of the gut and the food that's getting churned around inside the gut. Therefore, to prevent self-digestion, most organisms very carefully regulate the production of digestive enzymes, tuning production to both the timing and composition of the food they've just eaten.

This entry was originally posted at http://rebeccmeister.dreamwidth.org/1151317.html. Please comment there using OpenID.


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