Blue-tongued skinks of the genus Tiliqua (Scincidae) are characterized by their large blue melanin-pigmented tongues, often displayed during open-mouth threats, when the animal feels endangered. It is not clear whether this unusual coloration is a direct anti-predation adaptation or it may rather serve intraspecific communication, as ultraviolet-blue color is a frequent visual signal in a number of lizard species. We used spectrophotometry and visual modeling to compare blue tongues of Tiliqua gigas with tongues and skin coloration of other lizard species, and to examine their appearance through the eyes of both the conspecifics and avian predators. Our results show that (1) the tongue coloration is probably not substantially influenced by the amount of melanin in the skin, (2) lingual and oral tissues are UV-reflective in general, with blue colored tongues having chromatic qualities similar to UV-blue skin patches of other lizard species, (3) UV-blue tongues are more conspicuous than pink tongues, especially in the visual model of conspecifics. We hypothesize that blue tongues may possibly serve as a semantic (honest) signal analogous to UV-blue skin patches of other lizard species due to greater UV-bias in the vision of diurnal lizards. Regarding the social behavior and high aggressiveness in Tiliqua and their relatives, such signal might serve, e.g., in intraspecific long-distance communication between conspecifics in order to avoid aggression, and its anti-predation effect may only be a secondary function (exaptation).

proximate control of the development of sexual dimorphism is still hotly debated in reptiles. in some squamates, many male-typical exaggerated traits including body size were assumed to be controlled by masculinization by male gonadal androgens. We performed a manipulative experiment to test the importance of this mechanism in the development of pronounced sexual differences in body size and size of head casque in the chameleon Chamaeleo calyptratus. castrated males attained maletypical body size highly deviating from the body size of control females. ontogenetic allometries of casque size on head length revealed that sexes depart considerably in casque growth later in the ontogeny; however, castrated males still follow male-typical casque growth. paradoxically, exogenous testosterone led in females to slight increase of casque size, which might reflect interference with the feminizing effects of female gonadal hormones. The results in males strongly suggest that masculinization by male gonadal androgens during growth is not required for the development of sexual dimorphism in body size and casque size in the chameleon. the ontogeny of sexually dimorphic body size and exaggerated traits in at least some squamates is likely controlled by other proximate mechanism, possibly by feminization by ovarian hormones. Body size is one of the most prominent sexually dimorphic traits in animals. Squamate reptiles, an important group of vertebrates with a huge variability in body size, represent no exception. In many lineages of squamates, even closely related species may differ in the magnitude and also in the direction of sexual dimorphism in body size 1-4. Despite several studies, the proximate mechanism allowing this notable evolutionary plasticity in sexual dimorphism in body size is still poorly understood and several hypotheses on the proximate mechanisms responsible for the ontogeny of sexual dimorphism in body size have been suggested for squamates 2-7. The most hotly debated is the male androgen hypothesis suggesting that male growth is masculinized by gonadal androgens. Sex-specific levels of gonadal steroids are generally important for the control of sexually dimorphic traits in vertebrates 8 and the expression of many male-typical morphological, physiological and behavioural traits has been linked to the levels of male gonadal androgens present in squamates (e.g., size of copulatory organs 9 , activity of scent glands 10 , colouration 11 , odour and other sex recognition cues 12 , social behaviour 13,14). Nevertheless, the evidence that the growth of rigid, skeletal structures, for example total structural body size, is solely under the control of male gonadal androgens, is equivocal. Cox et al. 3 presented broader evidence for the bipotential effect of gonadal androgens which assumes that male gonadal androgens masculinize growth with a growth-stimulating effect in male-larger species and a growth-suppressing effect in female-larger species 2,3. This hypothesis was supported mainly by experiments on members of t...

Distinguishing between species is an essential aspect of animal research and conservation. For turtles, morphology and genetic analysis are potentially valuable tools for identification. Shell shape is an important component of phenotypic variation in turtles and can be easily described and quantified by geometric morphometrics (GM). Here, we focus on carapace and plastron shape discrimination of immature Southeast Asian box turtles (Cuora amboinensis) from two of the Greater Sunda Islands with partially distinct faunas. GM analysis identified significant differences in carapace and plastron shape between turtles from Borneo and Sumatra. The discrimination success amounted to 90% and 83.7% for carapace and plastron, respectively. The correlations of carapace and plastron shapes were high for Sumatra (0.846), and less pronounced for Borneo (0.560). We detected no differences in the ontogenetic trajectories of the shell shape between the two islands. We conclude that shell shape can be used for reliable geographic assignment of C. amboinensis of unknown origin. In addition to the comparison of shell shapes, turtles from Borneo, Sumatra, Seram, and turtles of unknown origin from two Czech zoos were studied genetically. Analysis of the complete mitochondrial cytochrome b gene confirmed the distinctness of turtles from Borneo and Sumatra, with p-distance 2.68 – 4.09% sequence difference. Moreover, we discovered considerable genetic difference in Seram turtles of previously unknown haplogroup (p-distance 6.00 – 8.68%) revealing the need for the revision of the whole species complex of Cuora amboinensis.