Hamilton Jamora A, Wada-Katsumata Ayako, Schal Coby
Department of Entomology and Plant Pathology, and W.M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC.
Environ Entomol. 2019 Jun 7;48(3):546-553. doi: 10.1093/ee/nvz044.
Aggregation can be adaptive by providing protection from predators, facilitating thermoregulation, and expediting the location of food, shelter, and mates. German cockroaches Blattella germanica L. (Blattodea: Ectobiidae), are obligatory commensals in human-built structures, where they aggregate in crevices during the day. The source of the aggregation pheromone that drives this behavior and its chemical identity remain unclear. Cuticular hydrocarbons (CHCs) in feces have been proposed to serve as aggregation pheromone, but this function has not been investigated in relation to visual and tactile cues that mediate aggregation. Our objective was to delineate how CHCs in the feces and on the cockroach body operate in conditions that reflect the German cockroach's ecology-either applied to shelters, representing fecal deposition, or to previously extracted cockroaches, representing shelter co-habitation with other cockroaches. Cockroaches and feces-conditioned filter papers were extracted, CHCs were purified by flash chromatography, and two-choice behavior assays were performed with first instar nymphs. Our results confirmed that nymphs preferred to rest within feces-conditioned shelters. However, purified CHCs did not elicit more aggregation than solvent-treated control shelters. Nymphs significantly preferred to rest in shelters that contained a CHC-free dead female, but the addition of CHCs to the female did not enhance aggregation. Nymphs preferred to aggregate with the CHC-free female over CHC-treated shelters. Finally, a methanol extract of feces was highly effective at eliciting aggregation, contesting previous reports that fecal CHCs serve as aggregation pheromone. We assert that CHCs play a minor, if any, role in the aggregation behavior of German cockroaches.
聚集行为具有适应性，它能提供抵御捕食者的保护，促进体温调节，并加快食物、庇护所和配偶的定位。德国小蠊（Blattella germanica L.，蜚蠊目：姬蠊科）是人类建筑结构中的专性共生昆虫，它们白天在缝隙中聚集。驱动这种行为的聚集信息素的来源及其化学特性仍不清楚。粪便中的表皮碳氢化合物（CHCs）被认为可作为聚集信息素，但尚未针对介导聚集的视觉和触觉线索对其功能进行研究。我们的目标是描绘粪便中和蟑螂体表的CHCs在反映德国小蠊生态的条件下如何发挥作用——要么应用于庇护所，代表粪便沉积，要么应用于先前提取过的蟑螂，代表与其他蟑螂共同栖息在庇护所中。提取蟑螂和经粪便处理的滤纸，通过快速柱色谱法纯化CHCs，并对一龄若虫进行双选行为测定。我们的结果证实，若虫更喜欢在经粪便处理的庇护所内休息。然而，纯化后的CHCs引发的聚集并不比溶剂处理的对照庇护所更多。若虫显著更喜欢在含有无CHC的死雌虫的庇护所中休息，但向雌虫添加CHCs并没有增强聚集效果。与经CHC处理的庇护所相比，若虫更喜欢与无CHC的雌虫聚集。最后，粪便的甲醇提取物在引发聚集方面非常有效，这与之前关于粪便CHCs作为聚集信息素的报道相矛盾。我们认为，CHCs在德国小蠊的聚集行为中即使有作用也是次要的。
