Cockroaches communicate via bacteria in their feces

first_img Click to view the privacy policy. Required fields are indicated by an asterisk (*) Like people, cockroaches like to hang out together, especially when they have nothing else to do. Now, researchers know why. Gut bacteria pooped along with their feces emit odors that the roaches find attractive. When those bacteria are missing, cockroaches tend to go it alone, researchers have discovered. Gut microbes in other organisms may likewise influence behavior in ways we have yet to appreciate.“We don’t know whether microbes are generally important in mediating chemical communications, but my best guess is that it’s widespread,” says Angela Douglas, who studies microbes and their animal hosts at Cornell University and was not involved with the work. Eavesdropping on microbe-cockroach conversations could lead to better ways to control this common household pest.Insects typically communicate using odors called pheromones; those that attract males to females are well-studied. Since the 1970s, entomologists have also known that so-called aggregation pheromones encourage roaches to stick close to one another. But researchers never could agree on what those pheromones really are. Some suggested they were waxy substances in the outer skin; others argued they were nitrogen-rich compounds in the feces; and a third group insisted that fatty acids—building blocks for fat—were involved, although which ones exactly was under debate. Sign up for our daily newsletter Get more great content like this delivered right to you! Country Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwecenter_img Email Coby Schal, an entomologist at North Carolina State University (NC State) in Raleigh wondered whether the conflicting results meant that different cockroaches depend on different aggregation chemicals because of variation in their environments, food, or gut microbes. So Schal and his team, including NC State entomologist Ayako Wada-Katsumata sterilized German cockroaches, Blattella germanica, and raised them in germ-free cages, so their feces would be germ-free. Usually cockroaches are attracted to their neighbors’ feces, but they tended to avoid the germ-free stuff.About 80% to 100% of young cockroaches tested preferred feces over sterile water, and although the difference in attraction was not as clear-cut between extracts of germ-free and normal feces, there were significantly more cockroaches aggregating by the normal feces extract, the researchers report online today in the Proceedings of the National Academy of Sciences. Without the microbes in the feces, the cockroaches no longer banded together very much. “The aggregation properties decline tremendously,” Schal says.When Wada-Katsumata isolated feces bacteria and fed them to the germ-free cockroaches, the roaches once again tended to form groups. Sophisticated chemical analyses of normal roach poop and germ-free poop showed that the latter lacked many of the usual fatty acids that evaporate from the feces once it is exposed to air; the researchers conclude these volatile fatty acids may be the missing aggregation pheromones. Synthetic versions of these compounds also cause cockroaches to aggregate.“This study explains how different studies in the past have yielded different results,” Douglas says. “It all depends on the microorganisms.” This may be why fatty acid advocates couldn’t agree on which fatty acids were important. Schal says that other candidate aggregation substances, in high concentrations, also seem to help bring the insects together, but these bacteria-produced compounds are much more potent and may be the most important drivers, Coby says.Other researchers have shown that a specific microbe hosted by desert locusts helps induce crowding behavior in that species. And in 2012, researchers suggested that bacteria living in hyenas’ scent glands impart the odors that help these animals tell kin from nonkin or pick out group members. “There’s the potential for this to be widespread,” Schal says.May Berenbaum, an entomologist at the University of Illinois, Urbana-Champaign, who was not involved with the work agrees. “It has become abundantly clear that insects partner with a tremendous diversity of microbial [associates]—bugs are bug-infested, as it were,” she points out. And in cockroaches, they “produce a beautiful story of biological cooperation.”And how about people? What we eat affects the bacteria in our guts, which in turn can affect what we smell like. But although the resulting foul body odor may deter contact, “there’s no evidence the bacteria play a positive role in communication among humans,” Schal says.He is now studying whether every population of cockroaches (even the ones living in your kitchen versus the ones in your basement) makes its own special aggregation pheromone. Schal and his colleagues hope to develop a synthetic aggregation pheromone that works for all German cockroaches. Such a compound would help lure roaches to insecticides, baits, and traps, Douglas says: “If we can understand the chemistry of cockroach aggregation and its plasticity better, we can devise better strategies for control.”last_img