Alarm communication predates eusociality in termites

Abstract

Termites (Blattodea: Isoptera) have evolved specialized defensive strategies for colony protection. Alarm communication enables workers to escape threats while soldiers are recruited to the source of disturbance. Here, we study the vibroacoustic and chemical alarm communication in the wood roach Cryptocercus and in 20 termite species including seven of the nine termite families, all life-types, and all feeding and nesting habits. Our multidisciplinary approach shows that vibratory alarm signals represent an ethological synapomorphy of termites and Cryptocercus. In contrast, chemical alarms have evolved independently in several cockroach groups and at least twice in termites. Vibroacoustic alarm signaling patterns are the most complex in Neoisoptera, in which they are often combined with chemical signals. The alarm characters correlate to phylogenetic position, food type and hardness, foraging area size, and nesting habits. Overall, species of Neoisoptera have developed the most sophisticated communication system amongst termites, potentially contributing to their ecological success.

Differentiation of workers into soldiers is associated with a size reduction of higher-order brain centers in the neotropical termite Procornitermes araujoi

“…The latter include cuticular hydrocarbons, which act as social recognition pheromones, as well as alarm and trail pheromones secreted by the frontal and sternal glands, respectively 60 , 77 . The emergence of alarm pheromones is suggested to have occurred only within MP termite species, which may face different challenges outside the nest and use these volatiles to alert nestmates 78 . Moreover, it has been shown that the secretion from the frontal gland of P. araujoi soldiers triggers an alarm response from conspecifics and is equally perceived by other soldiers and workers, which become aggressive 79 .…”

Juvenile Hormone Involved in the Defensive Behaviors of Soldiers in Termite Reticulitermes aculabialis

“…To protect colonies from omnipresent threats such as predators, termites have evolved diverse defensive strategies, including mechanical and chemical defenses. The mechanical defense includes locomotion, mandibular threats, head-banging, tremulation, touching and grooming [1][2][3]. Due to their specialized mandibles, termite soldiers are more focused on defensive functions than workers in the colony [4].…”

“…The first three behaviors were considered to transmit alarm messages to other termites [9], such as head-banging which results in vibrations in the substratum, triggering escape among workers and thereby acting as an alarm communication signal that spreads throughout the whole group via positive feedback [10], and mandible opening-closing for releasing defensive pheromones from the head of the soldier [11]. These diversely defensive strategies result from a plethora of evolutionary changes to increase the collective survivorship of the individuals participating in communal life [3,11]. The reports on the molecular mechanisms driving defensive behavior in termite colonies are growing in number, but most of the studies focus on the worker and few studies are reported on the soldier [12,13].…”

Termite exocrine systems: a review of current knowledge

“…Such a number is a likely consequence of the higher diversity of species and chemical communication in the latter group, especially within ants (Billen 2009a). Moreover, termite communication strongly relies on vibroacoustic signals (Sillam‐Dussès et al 2023). Nevertheless, termites display some exclusive glands, without any equivalent report for other insect taxa, as in the case of the frontal, nasus, and crystal glands, which might be intimately related to the complex social life evolved in this group (Costa‐Leonardo & Haifig, 2010a; Šobotník et al, 2012, 2015).…”