Endocrine control of cuticular hydrocarbon profiles during worker-to-soldier differentiation in the termite Reticulitermes flavipes E. Darrouzet ⇑ , M. Labédan, X. Landré, E. Perdereau, J.P. Christidès, A.G. Bagnères University of Tours, IRBI UMR CNRS 6172, parc de Grandmont, 37200 Tours, France article info Article history: Received 29 August 2013 Received in revised form 12 December 2013 Accepted 18 December 2013 Available online 27 December 2013 Keywords: Juvenile hormone Chemical signature Caste differentiation Soldier abstract The social organization of termites, unlike that of other social insects, is characterized by a highly plastic caste system. With the exception of the alates, all other individuals in a colony remain at an immature stage of development. Workers in particular remain developmentally flexible; they can switch castes to become soldiers or neotenics. Juvenile hormone (JH) is known to play a key role in turning workers into soldiers. In this study, we analyzed differences in cuticular hydrocarbon (CHC) profiles among castes, paying particular attention to the transition of workers to soldiers, in the subterranean termite species Reticulitermes flavipes. CHCs have a fundamental function in social insects as they serve as cues in inter- and intraspecific recognition. We showed that (1) the CHC profiles of the different castes (workers, sol- diers, nymphs and neotenics) are different and (2) when workers were experimentally exposed to a JH analog and thus induced to become soldiers, their CHC profiles were modified before and after the worker-presoldier molt and before and after the presoldier-soldier molt. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Unlike in other social insects like bees, wasps or ants, social organization in termites is highly plastic. An important feature of termite social organization is the caste system. Termites are hemi- metabolous insects and, except for the primary reproductives (alates), all individuals remain at an immature stage of develop- ment. They are organized into castes (workers, soldiers, nymphs and reproductives) that result from larval polyphenism (Korb and Katrantzis, 2004). Workers’ development is plastic; they can switch to another caste, becoming soldiers or secondary reproductives (i.e. apterous neotenics) or even develop regressively into a former in- star, which is a unique developmental pattern (Korb and Katrant- zis, 2004). As a result, individuals from the same colony with the same genetic background can develop different phenotypes (or into different castes) depending on intrinsic and/or extrinsic fac- tors (Scharf et al., 2007). One such intrinsic factor is endocrinal: exposure to juvenile hormone (JH) (Mao et al., 2005; Park and Raina, 2005; Scharf et al., 2003). This hormone is produced by the corpora allata, a pair of neurosecretory glands, and has a broad range of developmental and physiological effects (Gilbert et al., 2000). JH plays several roles: it controls larval/nymphal develop- ment and metamorphosis, diapause, migratory behavior, wing length, reproduction and caste determination (Hartfelder, 2000). JH is also involved in termite caste polyphenism (Mao et al., 2005; Park and Raina, 2004), especially when individuals differen- tiate into soldiers (Hartfelder and Emlen, 2005; Miura, 2001; Scharf et al., 2003) and probably when they differentiate into neotenics (Elliott and Stay, 2007, 2008; Leniaud et al., 2011). Different forms of JH have been found in insects (Darrouzet et al., 1998; Darrouzet and Desneux, 2013); however, JH-III is the only JH moiety released by the termite corpora allata (Brent et al., 2005) and detected in hemolymph (Brent et al., 2005; Cornette et al., 2008; Park and Raina, 2004). In termites, it is now well known that JH induces the differentiation of workers into presoldiers and then into sol- diers (Brent, 2009; Morel and Blum, 1988; Park and Raina, 2004). Several studies have shown that ectopic exposure of workers to JH-III readily induces their differentiation into soldiers (Scharf et al., 2003, 2005, 2007; Tarver et al., 2009, 2010; Zhou et al., 2006a,b, 2007). In 1972, Hrdy and Krecek similarly induced differ- entiation by ectopically applying a JH analog (JHA). Their results demonstrate that JH can act via exogenous exposure. Moreover, other studies have demonstrated that, under natural conditions, an increase in JH hemolymph titers in workers can cause them to differentiate into soldiers (Mao et al., 2005; Park and Raina, 2004). A brief peak in JH production is sufficient to induce such dif- ferentiation (Cornette et al., 2008). The insect cuticle is covered by a thin lipid layer largely consist- ing of cuticular hydrocarbons (CHCs). Because of their chemical properties, CHCs primarily act to limit insect water loss by creating a surface barrier (Blomquist and Dillwith, 1985; Gibbs and Pomonis, 1995; Hadley, 1985). However, they also serve as recognition cues. Inter- and intraspecific recognition among insects involve CHCs, which constitute the chemical signatures of individuals (reviewed by Blomquist and Bagnères, 2010; Howard 0022-1910/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jinsphys.2013.12.006 ⇑ Corresponding author. Tel.: +33 02 47 36 71 60; fax: +33 02 47 36 73 56. E-mail address: eric.darrouzet@univ-tours.fr (E. Darrouzet). Journal of Insect Physiology 61 (2014) 25–33 Contents lists available at ScienceDirect Journal of Insect Physiology journal homepage: www.elsevier.com/locate/jinsphys