Pheromone Autodetection: Evidence and Implications

Abstract

Olfactory communication research with insects utilizing sex pheromones has focused on the effects of pheromones on signal receivers. Early pheromone detection studies using the silkworm moth, Bombyx mori L., and Saturniids led to the assumption that emitters, especially females, are unable to detect their own pheromone. Pheromone anosmia, i.e., the inability of females to detect their conspecific sex pheromone, was often assumed, and initially little attention was paid to female behaviors that may result from autodetection, i.e., the ability of females to detect their sex pheromone. Detection of conspecific pheromone plumes from nearby females may provide information to improve chances of mating success and progeny survival. Since the first documented example in 1972, numerous occurrences of autodetection have been observed and verified in field and laboratory studies. We summarize here a significant portion of research relating to autodetection. Electrophysiological and behavioral investigations, as well as expression patterns of proteins involved in pheromone autodetection are included. We discuss problems inherent in defining a boundary between sex and aggregation pheromones considering the occurrence of autodetection, and summarize hypothesized selection pressures favoring autodetection. Importance of including autodetection studies in future work is emphasized by complications arising from a lack of knowledge combined with expanding the use of pheromones in agriculture.

A cytochrome P450 gene plays a role in the recognition of sex pheromones in the tobacco cutworm, Spodoptera litura

“…Only the CYP genes with male antennal and olfactory specific expression, such as PdivCYP4AW1 , were verified as pheromone‐degrading enzyme genes (Maïbèche‐Coisne et al ., ). In fact, sex pheromones can be auto‐detected by female moths (Holdcraft et al ., ; Stelinski et al ., ). Receptor cells specific for sex pheromone components were also found in S. littoralis female antennae and the sensitivity of the pheromone receptors was similar to those of males, whereas the number of pheromone‐specific sensilla was much lower in females (Ljungberg et al ., ).…”

“…Previous studies have always excluded genes not exclusively expressed in the male antennae, which resulted in a lack of knowledge on the molecular mechanisms of sex pheromone recognition, including the olfactory receptors (Krieger et al, 2004) Only the CYP genes with male antennal and olfactory specific expression, such as PdivCYP4AW1, were verified as pheromone-degrading enzyme genes (Ma€ ıbè che- Coisne et al, 2004). In fact, sex pheromones can be auto-detected by female moths (Holdcraft et al, 2016;Stelinski et al, 2014). Receptor cells specific for sex pheromone components were also found in S. littoralis female antennae and the sensitivity of the pheromone receptors was similar to those of males, whereas the number of pheromone-specific sensilla was much lower in females (Ljungberg et al, 1993).…”

Molecular elements of pheromone detection in the female moth, Heliothis virescens

“…In contrast, in females, the detection of the minor sex pheromone component is considered as basis for recognizing the presence of conspecific females. The ability of female moths to “autodetect” components of their own pheromone has been reported for several moth species (Holdcraft et al ., ) and it has been proposed that it may help female moths to escape competition for mating partners, ecological resources or oviposition sites (Harari & Steinitz, ). Alternatively, it is possible that “autodetection” triggers physiological responses in females.…”

“…Early studies on Bombyx mori and other moth species have led to the notion that females are generally anosmic for their own pheromone (Schneider, ). However, over the last decades numerous electrophysiological and behavioral studies have shown for a variety of lepidoteran species (reviewed in Holdcraft et al ., ) that female moths have the ability to recognize components of the pheromone they release; this phenomenon was designated as “autodetection” (Ochieng et al ., ; Schneider et al ., ; Bakthavatsalam et al ., ). This term could suggest self‐detection of compounds released by the pheromone‐producing individual, however, all the reported cases describe a detection of pheromones released by conspecific females (Holdcraft et al ., ).…”

“…However, over the last decades numerous electrophysiological and behavioral studies have shown for a variety of lepidoteran species (reviewed in Holdcraft et al ., ) that female moths have the ability to recognize components of the pheromone they release; this phenomenon was designated as “autodetection” (Ochieng et al ., ; Schneider et al ., ; Bakthavatsalam et al ., ). This term could suggest self‐detection of compounds released by the pheromone‐producing individual, however, all the reported cases describe a detection of pheromones released by conspecific females (Holdcraft et al ., ). The detection of a sex pheromone plume released by nearby females appears to trigger a reduced competition between females for ecological resources (Harari & Steinitz, ).…”