The effect of mating on the sex pheromone system of the yellow mealworm beetle, Tenebrio molitor L. (Coleoptera: Tenebrionidae). (March 2020) - Griffith, Obi L.
Abstract: The mating behavior of the yellow mealworm beetle ( Tenebrio molitor L.) is mediated by several pheromones, including a female-produced male attractant, (R)-(+)-4-methylnonanol (4-MNol); a male-produced female attractant, ( Z )-3-dodecenyl acetate; a male-produced anti-aphrodisiac; and at least one copulation pheromone. The objective of this study was to investigate the effect of mating on this complicated pheromone system. Glass rod bioassays were conducted to determine the response of virgin adult male beetles to the surface extracts of adult female beetles, prepared from virgin females, females allowed to mate once (extracted 0, 0.5, 1 or 2 h after mating), and females allowed to mate over an extended period of time (0, 1, or 21 h). Mating caused an immediate but temporary inhibition of the ability of the female extracts (FEs) to attract the males. This wore off relatively quickly, since FEs prepared 0.5–1 h after mating were as attractive as the virgin FE. Two hours after mating a second inhibition of attraction was observed, which was likely due to a drop in the titer of 4-MNol. Gas chromatographic analyses confirmed that the level of 4-MNol dropped after mating, from ∼40 ng per virgin female to below our levels of detection in mated females. A single mating event, or the 1 h extended mating, did not significantly affect the ability of the FEs to elicit copulation behavior (CB) from the males. However, FEs prepared after an extended mating (21 h) were significantly less able to attract males and to elicit CB. This is the first in depth study of the effect of a single and extended mating on sex pheromone production by a coleopteran species. In the long term, a greater understanding of the regulation of pheromone production could be useful for the manipulation of pest populations. Highlights: Male Tenebrio molitor likely deposited an anti-aphrodisiac during mating, which transiently inhibited further mating. The level of the male sex attractant pheromone, 4-methylnonanol, declined in females by about two hours after mating. Extended mating caused a decline in both the attractiveness and the ability to elicit copulatory behavior from the males. A post-mating decline in pheromone production might be adaptive for males and females: further study is required.