Influence of ovarian maturity, age, and mating status on the antennal responses of wild and laboratory reared Xyleborus affinis (Coleoptera: Curculionidae: Scolytinae) to ethanol.

Abstract

Xyleborus affinis Eichthoff is a neotropical ambrosia beetle that, in certain regions such as the United States and Mexico, has been associated with exotic phytopathogenic fungi causing extensive tree mortality. Although studies relating its olfactory response to volatile compounds and trapping systems have been published, factors such as the insect's physiological condition, which can affect its recognition or response to odors, have not been studied. Here, we evaluated the electroantennographic (EAG) response of wild and laboratory reared X. affinis females to 70% ethanol, a compound known to attract these insects. The experimental design was developed to consider and compare the following conditions: (i) females collected inside and outside host-galleries, (ii) sexual maturity (with mature and immature ovaries), (iii) age (0, 1, 3, and 5 d after emergence), and (iv) mating status (virgins and mated). Our results indicate that most of the wild females located outside the galleries were sexually mature but exhibited significantly lower EAG response than those inside the galleries. Regarding mating status, mated females exhibited significantly stronger antennal responses compared to virgins, whereas age did not affect antennal sensitivity. Finally, we provide images of the hitherto undescribed reproductive system of X. affinis females, a key element that enabled this investigation. The information generated offers a useful foundation for future studies aimed at understanding the physiological mechanisms and other critical factors related to sensory perception and reproductive condition. For example, factors that may influence the behavior and attraction of X. affinis females to host semiochemicals.