Contents lists available at ScienceDirect Hormones and Behavior journal homepage: www.elsevier.com/locate/yhbeh To fight or mate? Hormonal control of sex recognition, male sexual behavior and aggression in the gecko lizard Tereza Schořálková, Lukáš Kratochvíl ⁎ , Lukáš Kubička Faculty of Science, Charles University, Department of Ecology, Viničná 7, 128 43 Praha 2, Czech Republic ARTICLE INFO Keywords: Aggressive behavior Androgens Lizard Sexual behavior Sexual dimorphism Sex recognition Testosterone Dihydrotestosterone ABSTRACT Squamate reptiles are a highly diversified vertebrate group with extensive variability in social behavior and sexual dimorphism. However, hormonal control of these traits has not previously been investigated in sufficient depth in many squamate lineages. Here, we studied the hormonal control of male sexual behavior, aggres- siveness, copulatory organ (hemipenis) size and sex recognition in the gecko Paroedura picta, comparing ovar- iectomized females, ovariectomized females treated with exogenous dihydrotestosterone (DHT), ovariectomized females treated with exogenous testosterone (T), control females and males. The administration of both T and DHT led to the expression of male-typical sexual behavior in females. However, in contrast to T, increased circulating levels of DHT alone were not enough to initiate the full expression of male-typical offensive ag- gressive behavior and development of hemipenes in females. Ovariectomized females were as sexually attractive as control females, which does not support the need for the demasculinization of the cues used for sex re- cognition by ovarian hormones as suggested in other sauropsids. On the other hand, our results point to the masculinization of the sex recognition cues by male gonadal androgens. Previously, we also demonstrated that sexually dimorphic growth is controlled by ovarian hormones in P. picta. Overall, it appears that individual behavioral and morphological sexually-dimorphic traits are controlled by multiple endogenous pathways in this species. Variability in the endogenous control of particular traits could have permitted their disentangling during evolution and the occurrence of (semi)independent changes across squamate phylogeny. 1. Introduction Animal social behavior is one of the key components of life strate- gies. It is influenced by endogenous processes and, in the case of sexual and agonistic displays, mostly by circulating levels of gonadal steroids (reviewed e.g. in Adkins-Regan, 2005; Nelson, 2011). In many verte- brates, including squamate reptiles (Golinski et al., 2014, 2015; Mason and Adkins, 1976; Rhen and Crews, 1999; Sakata et al., 2002), the most significant hormone controlling the expression of male typical beha- viors is testosterone (T). Testosterone does not only act directly but also plays an important role as a prohormone and its effect can therefore be mediated through the action of its active metabolites. Testosterone can by aromatized to estradiol (E 2 ) or metabolized by 5α-reductase into the non-aromatizable androgen dihydrotestosterone (DHT). Both E 2 and DHT have been documented to control sexual and agonistic behavior in male vertebrates (e.g., Adkins and Schlesinger, 1979; Adkins-Regan, 1996; Heimovics et al., 2015; Huffman et al., 2013; Lindzey and Crews, 1986; Schlinger and Callard, 1990; Simon et al., 1998; Tokarz, 1986; Wu et al., 2009). Circulating testosterone can also be converted into its active metabolites locally by neurons and other brain cells expressing 5α-reductase and aromatase in various brain regions, where E 2 and DHT can be the major active hormones (e.g., Celotti et al., 1992; Unger et al., 2015; Wu et al., 2009). However, the regulatory effect of both E 2 and DHT on male sexual or agonistic behaviors is not universal among vertebrates. Simon et al. (1996) proposed that there are at least three regulatory pathways promoting male aggression: androgen-sensitive, involving T and its androgenic metabolites (as DHT); estrogen-sensitive, involving aromatization of T to E 2 ; or synergistic, combining both these regulatory types. The fourth suggested regulatory pathway assumes that only T could directly promote male-like aggressive behavior whereas its metabolites cannot; however, as far as we know, this me- chanism was supported only in a single mouse strain (Simon and Masters, 1987). Similarly, it also appears that the same regulatory pathways may occur in the control of male sexual behavior where the regulatory role of DHT or E 2 was confirmed in some (Adkins and Schlesinger, 1979; Adkins-Regan, 1996) but not all studied vertebrates (Crews et al., 1978; Rosen and Wade, 2000). One important question is whether male agonistic and sexual behaviors require organization by http://dx.doi.org/10.1016/j.yhbeh.2017.10.006 Received 19 June 2017; Received in revised form 11 October 2017; Accepted 12 October 2017 ⁎ Corresponding author. E-mail address: lukas.kratochvil@natur.cuni.cz (L. Kratochvíl). Hormones and Behavior 97 (2018) 18–24 0018-506X/ © 2017 Elsevier Inc. All rights reserved. MARK