A Review of Termite Pheromones: Multifaceted, Context-Dependent, and Rational Chemical Communications

Abstract

Termite colonies, composed of large numbers of siblings, develop an important caste-based division of labor; individuals in these societies interact via intra- or intercaste chemical communications. For more than 50 years, termites have been known to use a variety of pheromones to perform tasks necessary for maintenance of their societies, similar to eusocial hymenopterans. Although trail-following pheromones have been chemically identified in various termites, other types of pheromones have not been elucidated chemically or functionally. In the past decade, however, chemical compositions and biological functions have been successfully identified for several types of termite pheromones; accordingly, the details of the underlying pheromone communications have been gradually revealed. In this review, we summarize both the functions of all termite pheromones identified so far and the chemical interactions among termites and other organisms. Subsequently, we argue how termites developed their sophisticated pheromone communication. We hypothesize that termites have diverted defensive and antimicrobial substances to pheromones associated in caste recognition and caste-specific roles. Furthermore, termites have repeatedly used a pre-existing pheromone or have added supplementary compounds to it in accordance with the social context, leading to multifunctionalization of pre-existing pheromones and emergence of new pheromones. These two mechanisms may enable termites to transmit various context-dependent information with a small number of chemicals, thus resulting in formation of coordinated, complex, and rational chemical communication systems.

Ancestral sex-role plasticity facilitates the evolution of same-sex sexual behavior

“…In neoisopteran termites, including R. speratus, only females have strong sex-pairing pheromones. In contrast, there is no such sex difference in basal lineages, with both sexes emitting pairing pheromones in some species and both sexes lacking them in others (14,37). Our results, therefore, emphasize that the assumptions of recent models for the evolution of SSB via indiscriminate mate choice (8) are not always met: same-sex pairing in termites occurs even with strong sex discrimination.…”

Cuticular hydrocarbon profile for queen recognition in the termite Reticulitermes speratus

“…This study demonstrated that R. speratus uses a queen-speci c CHC pro le as a queen recognition pheromone to trigger aggregation of the workers, and suggests that R. speratus queens use both volatile compounds (as shown in Matsuura et al 2010) and non-volatile compounds as a signal to indicate the presence of the queen. Our study ndings strongly suggest that termites and social hymenopterans independently evolved the use of multicomponent queen signals by parsimonious use of CHCs for other purposes, enabling them to perform multifunctional roles (Le Conte et al 2008;Matsuura 2012;Leonhardt et al 2016;Hefetz 2019;Mitaka and Akino 2021). On the other hand, it is still unclear how AQS termites recognize the presence of a primary king in a colony because our GC-MS analysis did not detect any king-speci c or king-biased compounds (Tables S1 and S2 in the Electronic Supplementary Material).…”

Ancestral sex-role plasticity facilitates the evolution of same-sex sexual behaviour

“…3). In this clade, only females have sex-pairing pheromones, while in basal lineages, both females and males emit pairing pheromones [22,39]. Thus, the evolution of sexually dimorphic behaviour in tandems is clearly associated with the evolution of sex-specific signals, strongly arguing against a “mistaken identity” hypothesis of same-sex pairing in termites.…”