Chemical Identification, Emission Pattern and Function of Male-Specific Pheromones Released by a Rarely Swarming Locust, Schistocerca americana

Abstract

Pheromones serve key functions in the biology of swarming locusts. However, research has focused largely on the mass-swarming desert locust, Schistocerca gregaria. We extended these investigations to the pheromonal profile of the rarely swarming American bird grasshopper, S. americana (Drury). The headspace of mature gregarious S. americana males contained three characteristic electroantennogram-active components: (Z)-3-nonen-1-ol, (Z)-2-octen-1-ol, and nonanal. These substances were accompanied by aromatics such as phenol that are also released by females and immatures. Male-specific pheromone components were released independently from epidermal gland cells, with the highest emission rate being for (Z)-3-nonen-1-ol from the abdomen and legs. The emission of the major compound, (Z)-3-nonen-1-ol, is stress-sensitive, and coincides with sexual maturity and crowding. The emission pattern strongly supports a role of (Z)-3-nonen-1-ol in the reproductive biology of S. americana. The pheromone is involved in courtship-inhibition and is used as mate assessment pheromone in cryptic female choice. In double mating experiments, females choose sperm of males with high (Z)-3-nonen-1-ol emission. Furthermore the pheromone accelerated maturation of immature adults and supports synchronization of sexual development.

In Search for Pheromone Receptors: Certain Members of the Odorant Receptor Family in the Desert Locust Schistocerca gregaria (Orthoptera: Acrididae) Are Co-expressed with SNMP1

“…In the desert locust, the remarkable change between the solitary and the gregarious phase seems to be controlled by signaling compounds 1 . Thus, in Schistocerca gregaria , pheromones probably do not only play a central role in the reproduction process 31 , 32 but also may be essential for the phase change. In line with the existence of various pheromonal compounds for eliciting different behaviors or priming diverse physiological effects in desert locusts, our two-color FISH experiments revealed further SgreOR types that alike the b-OR group members were co-expressed with SNMP1 and thus can also be considered as candidate pheromone receptors.…”

“…In marked contrast to lepidopteran and dipteran species, the mechanisms of pheromone signaling in hemimetabolic insects are largely elusive although some pheromonal compounds have been identified in locusts 26 - 32 . The hemimetabolic locusts are only distantly related to holometabolic insects 33 .…”

“…Swarm formation is based on massive reproduction as well as aggregation. In locusts, both reproductive and aggregation behaviors are supposed to involve pheromones 1 , 27 , 32 , 35 , 36 and evidence has been accumulated that such pheromones elicit responses in antennal sensilla 31 , 37 - 39 . The antennal sensilla of locusts are categorized in distinct classes with the slender sensilla trichodea containing one to three OSNs and the broader and more massive sensilla basiconica comprising between 20 to 50 sensory neurons.…”

Identification and Characterization of Two “Sensory Neuron Membrane Proteins” (SNMPs) of the Desert Locust,Schistocerca gregaria(Orthoptera: Acrididae)

“…In addition, pheromones mediating courtship–inhibition have been observed in Schistocerca gregaria ( Seidelmann and Ferenz 2002 , Seidelmann et al. 2003 ) and the related species Schistocerca americana ( Stahr et al. 2013 ).…”

Evolutionary importance of intraspecific variation in sex pheromones

“…Other mechanisms that can affect pheromone production and release are pathogens [19], volatiles from host plants [31], conspecifics [35,36], or prey [37]. Verheggen et al [37] recently found that pheromone production in the Asian lady beetles (Harmonia axyridis) (Figure 1A) is conditioned by the presence of prey, as exposure to volatiles of the prey initiated pheromone production.…”