Parasite Rex
Jun. 18th, 2006 01:01 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
jinianA great book by Carl Zimmer, who blogs very well too. (That link fails for me but I think it's a browser problem.)
Parasites are amazing.
Further, the fungus compels the fly to do this just before sunset, when other flies will be low to the ground but not yet sheltered. We don't know the mechanism yet. Evolution is an amazing thing.
There's also the lancet fluke, Dicrocoelium dendriticum, which is the one that makes an ant sit on top of a grass blade so it can be eaten by a ruminant and the fluke's life cycle can progress.
Maybe I should watch THE FACULTY. From a parasitology point of view, it sounds quite entertaining.
There was a variant of the Red Queen hypothesis that I hadn't encountered before: it's parasites that lead to more sex among the hosts. This makes a lot of sense, since there can be multiple parasites per host species and gene combinations could be way more adaptive than a cloned line with just one advantageous gene.
Some leaf-rolling caterpillars eject their feces up to two feet; they don't move all that much, and parasitoid wasps can track host species by their droppings. (This is because parasitoid wasps rule.)
Some of the parasite problems humans have had aren't likely to come back, provided we remember to wash and cook food adequately and don't lose the capability to make effective drugs. Climate change could easily bring some problems back, though, particularly malaria, and we don't really know what social effects that could have.
There are positive aspects to playing host, though; parasite-free living may lead to autoimmune diseases. Parasites can suppress host immune cell activity, so we may have evolved an overclocked immune system in order to stay ahead of them; in that case, no parasites means a system that really really wants SOMETHING to do. I haven't heard yet whether deliberate hookworm infection has had much effect on allergy sufferers.
I say it again: awesome book. Parasitology is so interesting.
Parasites are amazing.
A fungus that lives inside house flies provides a spectacular example of this. When the spores of the fungus make contact with a fly, they stick to its body and dig tendrils into the fly's body. The fungus spreads throughout the fly's body with Sacculina-like roots and sucks up the nutrients of its blood, making the fly's abdomen swell as it grows. For a few days the fly lives on normally, flying from spilled soda to cow turd, using its proboscis to sponge up food. But sooner or later it gets an uncontrollable urge to find a high place, be it a blade of grass or the top of a screen door. It sticks out its proboscis but uses it as a clamp this time, gluing itself to its high perch.
The fly lowers its front legs, tilting its abdomen away from the surface. It flaps its wings for a few minutes before locking them upright. The fungus has meanwhile pushed its tendrils out of the fly's legs and belly. On the tips of the tendrils are little spring-loaded packages of spores. In this bizarre position, the fly dies, and the fungus catapults out of its corpse. Every detail of this death pose -- the height, the angles of the wings and the abdomen -- all put the fungus in a good position for firing its spores into the wind, to shower down on flies below.
Further, the fungus compels the fly to do this just before sunset, when other flies will be low to the ground but not yet sheltered. We don't know the mechanism yet. Evolution is an amazing thing.
There's also the lancet fluke, Dicrocoelium dendriticum, which is the one that makes an ant sit on top of a grass blade so it can be eaten by a ruminant and the fluke's life cycle can progress.
Maybe I should watch THE FACULTY. From a parasitology point of view, it sounds quite entertaining.
There was a variant of the Red Queen hypothesis that I hadn't encountered before: it's parasites that lead to more sex among the hosts. This makes a lot of sense, since there can be multiple parasites per host species and gene combinations could be way more adaptive than a cloned line with just one advantageous gene.
Some leaf-rolling caterpillars eject their feces up to two feet; they don't move all that much, and parasitoid wasps can track host species by their droppings. (This is because parasitoid wasps rule.)
Some of the parasite problems humans have had aren't likely to come back, provided we remember to wash and cook food adequately and don't lose the capability to make effective drugs. Climate change could easily bring some problems back, though, particularly malaria, and we don't really know what social effects that could have.
Most Americans don't know that in the 1800s, malaria's range swept all the way up the Great Plains into North Dakota, or that in 1901 a fifth of the population of Staten Island carried the parasite. Most don't know that people in the southern United States once had a reputation for being lazy and stupid because so many of them were being drained by hookworm. Most don't know that in the 1930s, 25 percent of the pork sold in the United States carried Trichinella.
There are positive aspects to playing host, though; parasite-free living may lead to autoimmune diseases. Parasites can suppress host immune cell activity, so we may have evolved an overclocked immune system in order to stay ahead of them; in that case, no parasites means a system that really really wants SOMETHING to do. I haven't heard yet whether deliberate hookworm infection has had much effect on allergy sufferers.
I say it again: awesome book. Parasitology is so interesting.
