{"68484":{"#nid":"68484","#data":{"type":"news","title":"Scientists Uncover an Unhealthy Herds Hypothesis","body":[{"value":"\u003Cp\u003EBiologists worldwide subscribe to the healthy herds\nhypothesis, the idea that predators can keep packs of prey healthy by removing\nthe weak and the sick. This reduces the chance disease will wipe out the whole\nherd, but could it be that predators can also make prey populations more\nsusceptible to other predators or even parasites? Biologists at the Georgia\nInstitute of Technology have discovered at least one animal whose defenses\nagainst a predator make it a good target for one opportunistic parasite. The research\nappears online in the journal \u003Cem\u003EFunctional\nEcology\u003C\/em\u003E\u003Cstrong\u003E.\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003E\u201c\u003C\/strong\u003EWe found that strategies that\nprey use to defend themselves against predators can increase their\nsusceptibility to infection by parasites,\u201d said Meghan Duffy, assistant\nprofessor in Georgia Tech\u2019s School of Biology.\u003C\/p\u003E\n\n\u003Cp\u003EDuffy,\nalong with colleagues at the University of Illinois at Urbana-Champaign and\nIndiana University, took a look at a small aquatic crustacean, \u003Cem\u003EDaphnia dentifera\u003C\/em\u003E, a water flea known to\nbe an important part of freshwater ecosystems. They exposed the crustacean to\nchemicals emitted by one of its predators, a phantom midge larva known as \u003Cem\u003EChaoborus\u003C\/em\u003E, known to feed on it. When the\n\u003Cem\u003EDaphnia\u003C\/em\u003E detected those chemicals it\ngrew larger, making it harder for its predator to get its mouth around it.\u003C\/p\u003E\n\n\u003Cp\u003E\u201cUnfortunately\nfor the\u0026nbsp;\u003Cem\u003EDaphnia\u003C\/em\u003E, this defense against predation\nmakes them more vulnerable to parasitism,\u201d said Duffy.\u003C\/p\u003E\n\n\u003Cp\u003EThat\u2019s\nbecause while growing larger keeps \u003Cem\u003EDaphnia\u003C\/em\u003E\nsafe from \u003Cem\u003EChaoborus\u003C\/em\u003E, it actually\nmakes it more susceptible to a virulent yeast parasite, known as \u003Cem\u003EMetschnikowia\u003C\/em\u003E. When \u003Cem\u003EDaphnia\u003C\/em\u003E senses a threat from its predator and\u003Cem\u003E \u003C\/em\u003Egrows larger, it ends up consuming more of these parasitic yeasts than\nit does when normal size. When the yeast infects the crustacean, it kills it,\ncausing the dead animal to release yeast spores as it decomposes. The larger\nthe host, the more spores it releases back into the water to prey on other \u003Cem\u003EDaphnia\u003C\/em\u003E.\u003C\/p\u003E\n\n\u003Cp\u003E\u201cSince\nthey need to grow larger to defend themselves against the predator but the\nopposite to defend against the parasite, they\u0027re sort of stuck between a rock\nand a hard place,\u201d she added.\u003C\/p\u003E\n\n\u003Cp\u003EDuffy\nreasons that this occurs because the predators are common year-round, while the\nparasites are more episodic in nature, with their populations expanding in\nepidemics only in the fall and not even yearly. This results in long periods of\npredation in the absence of the parasite, which probably explains why they\nrespond so strongly to defend themselves against the predator even though it\ndecreases their defenses against the yeast, she added.\u003C\/p\u003E\n\n\u003Cp\u003E\u201cWhile\nsome have argued for increasing predator densities to control disease, our\nresults suggest that it is important to consider the indirect effects of\npredators, such as the one we found in which trying to avoid one enemy\nincreases the hosts vulnerability to another,\u201d said Duffy.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cem\u003EThis research was\nfunded by the National Science Foundation\u003C\/em\u003E.\u003C\/p\u003E\n\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EBiologists worldwide subscribe to the healthy herds\nhypothesis, but could it be that predators can also make prey populations more\nsusceptible to other predators or even parasites? Biologists at the Georgia\nInstitute of Technology have discovered at least one animal whose defenses\nagainst a predator make it a good target for one opportunistic parasite. The\nresearch appears online in the journal \u003Cem\u003EFunctional\nEcology\u003C\/em\u003E\u003Cstrong\u003E.\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"One animals defense against prey can make it more susceptible to a parasite."}],"uid":"27310","created_gmt":"2011-06-23 08:37:03","changed_gmt":"2016-10-08 03:09:37","author":"David Terraso","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2011-06-23T00:00:00-04:00","iso_date":"2011-06-23T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"68416":{"id":"68416","type":"image","title":"Killer Larva Preys on Small Crustacean","body":null,"created":"1449177176","gmt_created":"2015-12-03 21:12:56","changed":"1475894592","gmt_changed":"2016-10-08 02:43:12","alt":"Killer Larva Preys on Small Crustacean","file":{"fid":"193322","name":"8c.jpg","image_path":"\/sites\/default\/files\/images\/8c_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/8c_0.jpg","mime":"image\/jpeg","size":52662,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/8c_0.jpg?itok=1fhg15zC"}},"68417":{"id":"68417","type":"image","title":"Parasite Grows in Crustacean","body":null,"created":"1449177176","gmt_created":"2015-12-03 21:12:56","changed":"1475894592","gmt_changed":"2016-10-08 02:43:12","alt":"Parasite Grows in Crustacean","file":{"fid":"193323","name":"inf_uninf_dissect_5.jpg","image_path":"\/sites\/default\/files\/images\/inf_uninf_dissect_5_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/inf_uninf_dissect_5_0.jpg","mime":"image\/jpeg","size":413157,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/inf_uninf_dissect_5_0.jpg?itok=36631w6J"}}},"media_ids":["68416","68417"],"groups":[{"id":"1183","name":"Home"}],"categories":[{"id":"146","name":"Life Sciences and Biology"}],"keywords":[{"id":"4896","name":"College of Sciences"},{"id":"3028","name":"evolution"},{"id":"13456","name":"Meghan Duffy"},{"id":"7631","name":"parasite"},{"id":"13478","name":"predator"},{"id":"13479","name":"prey"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EGeorgia Tech Media Relations\u003C\/strong\u003E\u003Cbr \/\u003ELaura Diamond\u003Cbr \/\u003E\u003Ca href=\u0022mailto:laura.diamond@comm.gatech.edu\u0022\u003Elaura.diamond@comm.gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-894-6016\u003Cbr \/\u003EJason Maderer\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-660-2926\u003C\/p\u003E","format":"limited_html"}],"email":["mattnagel@comm.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}