Chemical Ecology: Pheromones and other semiochemicals

Chemical signaling is fundamental for the survival and reproduction of most animals. Chemical cues allow animals to appraise their environment, to detect food, toxins, prey, predators and pathogens, to identify kin, and to evaluate and bias mate-choice decisions. Many insects depend on sex pheromones for the identification of reproductive partners and the onset of reproductive physiology and mating behavior. However, the prevalence and importance of chemical signaling in various insect groups depends on the natural history of the insects. Cockroaches are the quintessential chemical communicators. In contrast to the closely related grasshoppers and crickets, which rely on sound and vision as primary modalities in communication, cockroaches use olfactory and tactile signals in their social behavior. Most of the 4000+ described species of cockroaches are nocturnal. Many use long-range volatile pheromones in mate-finding and cuticular contact pheromones in the final recognition process. Short-range volatile pheromones emitted by the male, coupled with nuptial tergal secretions, facilitate proper alignment of the pair prior to copulation. Pheromones also mediate intrasexual conflicts, especially when males establish dominance hierarchies and territories, in parent-offspring communication, stage and population recognition, trail-following behavior, and as epidiectic pheromones that mediate dispersion behavior.

Pheromones

Right. An adult female German cockroach (top right) being courted by 3 males. Upon touching the female, the male perceives a multi-component contact pheromone that elicits courtship. The male turns away from the female and raises his wings, thus exposing a tergal secretion, and in this image, the female is mounting a male and is feeding on this secretion. Copulation follows.

Left. German cockroach females emit a volatile pheromone, Blattellaquinone, which attracts males from a distance. The pheromone is produced in a gland located in the last abdominal tergite. In this area the cuticle forms deep depressions in which a large number of cuticular orifices are located. These orifices are connected to secretory cells via cuticular ducts (blue) surrounded by duct cells (yellow).

Our research concentrates on sex pheromones that are used in mate-finding and recognition and aggregation pheromones that mediate group formation. Our current projects include:

Investigation of the anatomical sites, biochemical pathways, transport routes, and neuroendocrine regulation of pheromone production in cockroaches.
Role of contact pheromones in cockroach communication and courtship.
Behavioral studies of calling - the behavior responsible for emission of volatile pheromones.
Isolation, purification, and identification of pheromones.
Role of microbial symbionts in aggregation pheromone production.
Development of pheromone-based tools for monitoring, sampling, and controlling cockroach pest populations.

Our lab has had a long-term interest in studies of the behavioral ecology of temperate pest cockroaches and non-pest tropical rain-forest species. We are particularly interested in the evolution of mating systems, parental contributions and sexual gift-giving, and mate-finding tactics. Recently, we initiated studies of the mating system of Parcoblatta wood cockroach species. This genus is native to N. America and common in forests throughout the Southeast. Importantly, recent studies have shown that various Parcoblatta species represent an important ecological indicator because 50% of the diet of the endangered red-cockaded woodpecker, Picoides borealis, consists of wood cockroaches.

Recent Collaborations:
Walter Leal
Kenji Mori
Wendell Roelofs
Fran Webster

Supported by:
Blanton J. Whitmire Endowment

SCHAL LAB

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