We humans aren't the only animals that have to worry about bug bites. There are thousands of insect species that have evolved to specialize in feeding on different mammals and birds, but scientists are still learning how these bugs differentiate between species to track down their preferred prey. It turns out, the attraction might not even be skin-deep: a new study in Molecular Ecology found evidence that blood-sucking flies that specialize on bats may be locating their preferred hosts by following the scent of chemicals produced by bacteria on the bats' skin.
Holly Lutz, the paper's lead author, got the idea for the project from previous research showing that mosquitoes seem to prefer some people over others. "You know when you go to a barbeque and your friend is getting bombarded by mosquitos, but you're fine? There is some research to support the idea that the difference in mosquito attraction is linked to your skin microbiome -- the unique community of bacteria living on your skin," says Lutz, a research associate at Chicago's Field Museum and a project scientist with the labs of Jack Gilbert (who co-authored this study) and Rob Knight at the University of California, San Diego. "Keeping in mind that some people are more attractive to mosquitoes than others, I wondered what makes insects attracted to some bats but not others."
Lutz encountered plenty of bats during her PhD work and postdoctoral residency at the Field Museum, on fieldwork trips to bat caves in Kenya and Uganda studying malaria. "In these caves, I'd see all these different bat species or even taxonomic families roosting side by side. Some of them were loaded with bat flies, while others had none or only a few. And these flies are typically very specific to different kinds of bats -- you won't find a fly that normally feeds on horseshoe bats crawling around on a fruit bat." says Lutz. "I started wondering why the flies are so particular -- clearly, they can crawl over from one kind of bat to another, but they don't really seem to be doing that."
The flies in question are cousins of mosquitoes, and while they're technically flies, most can't actually fly. "They have incredibly reduced wings in many cases and can't actually fly," says Lutz. "And they have reduced eyesight, so they probably aren't really operating by vision. So some other sensory mechanisms must be at play, maybe a sense of smell or an ability to detect chemical cues."
??"How the flies actually locate and find their bats has previously been something of a mystery," says Carl Dick, a research associate at the Field Museum, professor of biology at Western Kentucky University, and one of the study's co-authors. "But because most bat flies live and feed on only one bat species, it is clear that they somehow find the right host."
Furthermore, bat flies transmit malaria between bats, and the malaria parasites are host-specific as well. It's an intricate, complex system with important parallels to other vector-borne pathways for disease transmission, such as malarial and viral transmission among humans by anopheline mosquitoes. Previous research has shown that different bacterial species associated with skin or even the disease status of individual humans can influence feeding preferences of blood-seeking mosquitoes.
Lutz suspected that, similarly to what's been observed in humans, the bats' skin microbiomes may be playing a role in attracting the flies seeking them out. Skin -- whether it belongs to a human or a bat -- is covered with tiny microorganisms that help protect the body from invading pathogens, bolster the immune system, and break down natural products like sweat. Host species evolve alongside their skin microbiomes, leading to different species being home to different sets of bacteria.
source :science daily
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