Last night I suddenly came down with a bad fever. When I called my mom (a pharmacist) today, she told me in no uncertain terms to take Ibuprofen. But that might be bad advice. Why?
Over a decade ago, Randolph Nesse and George Williams published an article in Science interpreting disease in an evolutionary context. It’s a fun and fascinating read about not just the arms race between ourselves and pathogens that attack us, but the value of some symptoms we abhor, like fevers and morning sickness. A rise in body temperature, they argue, can quickly fry microorganisms and even deactivate viruses living inside you. As the famous biologist Theodosius Dobzhanksy once wrote, “nothing in biology makes sense except in the light of evolution.”
Two years before that (1996), Klugor and colleagues had reviewed several studies and also concluded that fever might be beneficial to the host (me) in defeating its pathogens (this #@&! virus). Research in this area continues, with Jane Carey’s literature review just last year on whether treating fevers in hospitals actually helped the patients. She found the results were inconclusive, but that it could actually prolong a patient’s stay.
I should point out that high fevers can be bad for the host! You can denature your own proteins. That’s bad. So if the fever is getting really high, it is probably a good idea to treat it. Was mine high enough to worry? I don’t know; I didn’t take my temperature. Not very scientific, I know. But I’m hoping that by letting the fever run its course and sleeping it off, I have decreased the time that I will be sick.
Bedbugs (Cimex lectularius) were in the news in recent months for epidemic outbreaks in across the United States. A brand new study shows WHY they are even harder to kill than ever. Researchers at the Ohio State University sequenced the bedbug transcriptome, which means they isolated all the DNA that was being used by the bugs (there’s lots of “junk” in most genomes that is not transcribed, or used) and figured out the sequence of the nucleotides (the building blocks of the double helix). This has only recently become possible to do as quickly and cheaply as they did – and we’re still probably talking in the tens of thousands of dollars at least!
The researchers found a number of genes that detoxify pesticides being used frequently – much more frequently than a colony of bedbugs isolated since the 1970’s. This means the bedbugs have probably evolved higher pesticide resistance, which is why our usual pesticides aren’t getting rid of them easily anymore. Yikes!
Host-parasite interactions is the fancy ecologist word for what people and bedbugs are doing: they live on sucking human blood, we humans don’t like that, we try to kill or avoid them, and they try to get around our defenses. A LOT of research has been done both on the “arms race” of these systems (for example, we develop new pesticides and they develop new resistance) and to the ecological population dynamics on shorter time scales.
Some pairs of hosts and parasitoids have numbers that go in cycles, like spruce trees and budworms that attack them: the parasitoid feeds up on the hosts, killing them off, until the host population crashes. Since the parasitoids cannot find the hosts as well, their population declines, too. Then the hosts build up and it keeps going. Other pairs of species have surprisingly stable numbers, like the California red scale and a parasitoid introduced to control it. How these interactions function partly depends on the spatial scales of each species. Bedbugs seem to be good at dispersing with people traveling, and people are probably not going to decrease our population densities (move out of the cities) any time soon.
So are they here to stay? Given human ingenuity and our history of pesticide research, I bet we’ll come up with a defense. But sooner or later, the bed bugs will overcome that, too.
I have a confession to make: I don’t like long walks on the beach. It’s a classic line in a singles’ ad, but I just can’t make myself fit in there.
The problem is that I get bored. So I start looking around for things to entertain myself, and usually wind up with the local wildlife.
While visiting my sister for New Year’s in Panama, where she is a Peace Corps volunteer (more on her community and tropical agriculture later), we spent a few days at a nearby beach on the Pacific ocean. I saw shorebirds like great white egrets and collared plovers and an unidentified species of sandpiper. I saw fiddler crabs abandoning their sand-rolling feeding as I approached to dash into their sandy burrows. I watched tiny green worms and snails inscribe mysterious and winding pathways as they bid farewell to each wave.
I could hypothesize that the birds eat the crabs or worms or snails based on their size difference and the behavior of the birds pecking at the sand, but it would take much more observation and experiments to prove it. In fact, a number of important ecological studies have been done on Pacific beaches.
In 1964, Robert Paine did just that: he spent a year observing and experimenting on the food webs on the Olympic Peninsula in Washington. He published an article in American Naturalist (a prestigious scientific, peer-reviewed journal) titled “Food Web Complexity and Species Diversity.” Paine described an experiment where he kept the purple ochre starfish (Pisaster ochraceus) out of an area for nearly a year. While the species of barnacles, tunicates, and shellfish it fed on remained the same in a neighboring plot, where the starfish was excluded things began to change. One of the barnacles, Balanus glandula, took over 60-80% of the space within a few months, leaving little room for less efficient competitors. But it did not stop there. By the next summer, two other barnacles (Mytilus californianus and Mitella polymerus), tiny and fast-growing, were displacing everything else, even the B. glandula. Sponges and their nudibranch predators, algae, tunicates, and limpets all disappeared as well.
Paine was hardly the first to notice that predators had real effects on their prey’s populations – Aldo Leopold had written decades before of the trophic cascade that resulted when eliminating wolves in Arizona caused deer populations to explode and completely denude their mountainous habitat. Paine’s point was that the entire ecosystem became much less diverse in species and simpler in food webs without that top predator. This was a big deal in ecological thinking: that predation could change the outcome of species’ competition for space!
Of course, now we know that predation goes further than just changing competition: it can have an equal and equally important impact on species diversity. So now I am left wondering which, if any, predators on the Panamanian beach are preserving the diversity I managed to capture in just one, long, boring walk on the beach.