A mammalian blood odor component serves as an approach-avoidance cue across phylum border - from flies to humans.

Chemosignals are used by predators to localize prey and by prey to avoid predators. These cues vary between species, but the odor of blood seems to be an exception and suggests the presence of an evolutionarily conserved chemosensory cue within the blood odor mixture. A blood odor component, E2D, has been shown to trigger approach responses identical to those triggered by the full blood odor in mammalian carnivores and as such, is a key candidate as a food/alarm cue in blood. Using a multidisciplinary approach, we demonstrate that E2D holds the dual function of affecting both approach and avoidance behavior in a predator-prey predicted manner. E2D evokes approach responses in two taxonomically distant blood-seeking predators, Stable fly and Wolf, while evoking avoidance responses in the prey species Mouse. We extend this by demonstrating that this chemical cue is preserved in humans as well; E2D induces postural avoidance, increases physiological arousal, and enhances visual perception of affective stimuli. This is the first demonstration of a single chemical cue with the dual function of guiding both approach and avoidance in a predator-prey predicted manner across taxonomically distant species, as well as the first known chemosignal that affects both human and non-human animals alike.

Semiochemicals released from five bacteria identified from animal wounds infested by primary screwworms and their effects on fly behavioral activity.

BACKGROUND: The Primary screwworm, Cochliomyia hominivorax (Coquerel), is a serious pest feeding on living flesh of any warm-blooded animal, including humans. It was eradicated from the United States in the early 1980s using the sterile male technique. However, it was recently detected in populations of wild deer and pets in the Florida Keys of the US. For monitoring purposes, screwworm flies are normally trapped using attractant bait with liver. However, there has been little effort to develop an efficient monitoring system for detection of screwworm flies using a specific synthetic attractant blend. Several studies have shown that odors from animal wound fluids attract screwworm adults, particularly gravid females. Bacteria associated with animal wounds have been identified that act as a major source for this attraction. To understand what volatiles attract screwworms we inoculated bovine blood with previously identified bacteria. We identified volatile chemicals released from the inoculated blood and other selected media over time and assessed the effect of those chemicals on behavioral activity of adult screwworm flies. METHODOLOGY/PRINCIPAL FINDINGS: A total of 7 volatile compounds were collected from bacteria incubated in either broth or blood using solid-phase microextraction, and their chemical structures were identified by their characteristic mass spectrum fragments and confirmed by retention times in comparison to those of synthetic standards via gas chromatograph combined mass spectrometry analyses. Five major volatiles including dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol and indole were detected from a mixture of 5 bacteria incubated in blood. The ratios of volatiles released differed among different incubation media, time and individual bacteria. A synthetic mixture containing the five compounds was demonstrated to be attractive to adult screwworm flies both in laboratory assays and field trapping trials. CONCLUSIONS/SIGNIFICANCE: The results obtained from this study may assist in developing an efficient trapping system using the identified attractant blend to detect the infestation of primary screwworms. This is also the first study to explore the complex systems in volatile release profiles from 5 bacteria isolated from screwworm-infested animal wounds that are incubated with different media and incubation time, as well as individual and multi-species bacterial communities.