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Pheromones in Desert Locusts

Hormonal control of pheromone biosynthesis in males of the desert locust, Schistocerca gregaria

Pheromones play a key function in the reproduction biology of desert locust, Schistocerca gregaria. Males of the desert locust use the pheromone phenylacetonitrile (PAN, syn: benzylcyanide) to chemically enhance their post-copulatory mate guarding in the gregarious phase at high population densities. PAN is rather an "courtship inhibiting pheromone" and "abstinone" than an aggregation pheromone. The biosynthesis of the pheromone is controlled by an neuropeptide PAN-BAN (PhenylAcetoNitrile-Biosynthesis Activating Neuropeptide). It is planed to purify and sequence this neuropeptide. Ongoing studies aim to clarify the relations between maturity, sexual behaviour, and colouration of adult S. gregaria males. Thereby we hope to enable first insights into neuro-hormonal control mechanisms of locust pheromones.

Phase polyphenism within the genus Schistocerca (desert locusts)

The African Desert locust (Schistocerca gregaria) has a distinct phase polymorphism that allows adaption to aperiodic changing environmental conditions. This capability to shift from a solitary phase toward a gregarious one and vice versa possess also other species of the genus Schistocerca. This opens the possibility to study the phenomenon of phase polyphenism in an taxonomic-systematical context. The aim of our study the function of pheromones in dependence of the degree of polyphenism developed in several species. Furthermore, the identification of the substances used as male pheromones provides valuable information on the evolution of the genus Schistocerca. This genus has a remarkable disjunct distribution pattern: The species that possesses the most extreme phase polyphenism, S. gregaria, lives in the Old World, while all other species are spread throughout the American continents. The American Schistocerca species express very different degrees of phase polyphenism.

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