Animals Have Evolved Into Parasites At Least 200 Times Today, around 40 percent of animal species are parasites.

When I ask Sara Weinstein about her favorite parasite, she laughs, and has a quick answer. “I think the flies that parasitize frogs are really interesting,” she says. There are many species of them, including two known as toadflies. The females lay their eggs on frogs and toads—sometimes on their skins and occasionally in their nostrils. When the maggots hatch, they eat their way inward, and you can sometimes see them through the wounds that they open in their host’s flanks. Their appetites are usually fatal. Once their hosts have ribbited their last, the larvae fall away and turn into adults. Many insects also get devoured alive by the larvae of parasitic wasps, flies, and more. But the idea of a back-boned animal—a vertebrate like ourselves—succumbing to a similar end is what really creeps Weinstein out. “We don’t think about vertebrates being affected by parasites that can take over the whole organism,” she says. “It’s like the movie Alien.” Parasites are those creatures that, at some point in their lives, survive by feeding on another individual. It’s easy—hopeful, perhaps—to think of them as oddities of nature, as grisly outliers that we would only encounter through extreme bad luck. But as I noted in my TED talk, parasitism is the rule rather than the exception. It’s estimated that around 40 percent of animal species are parasites. Forget elephants, hummingbirds, whales, and tortoises—pick a random animal, and it’s far more likely to be a blood-sucker, disease-carrier, host-castrator, or flesh-devourer. Indeed, as Weinstein and her advisor Armand Kuris have now shown, parasitism has evolved among animals at least 223 times—almost four times more than previous estimates of “around 60.” “More comprehensive explorations of parasite evolution would contribute much to our understanding of the evolution of life,” they write. The toadflies are what first got Weinstein, a graduate student at the University of California, Santa Barbara, hooked into parasitic animals. She wanted to understand how they evolve, and what happens once they do. You could imagine that once a group of animals takes up the parasitic lifestyle, they find a wealth of new hosts, or even environments within a host, to exploit. Perhaps, then, they rapidly diversify into a wide range of new species. Or perhaps they find themselves in an evolutionary dead end? They specialise on a particular host and get stuck, doomed to extinction if their host dies.

Read More: http://news.nationalgeographic.com/2016/07/animals-evolution-parasites-ed-yong/

Posted by admin on Jul 25 2016. Filed under News at Now. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry