Chemical characterization of the lipids in femoral gland secretions of wild male tegu lizards, Salvator merianae (Squamata, Teiidae) in comparison with captive-bred males

Although chemical interactions play an essential role in lizard social behavior, the chemical composition of the femoral gland secretions that many lizards use for communication is known for only a few species, mainly European Lacertids. The tegu lizard, Salvator merianae, is the only species of the Teiidae family for which there is available information on lipids in femoral secretions, but only for captive bred males from Argentina. Here, based on mass spectra obtained by GC-MS, we found 69 lipophilic compounds in femoral gland secretions of wild males S. merianae from Brazil, including cholesterol and high amounts of saturated fatty acids (mainly hexadecanoic and octadecanoic). We found contrasting differences between wild and captive-bred males, which lack cholesterol but present high amount of 9,12-octadecadienoic acid. These within-species differences between wild and captive lizards strongly suggest the important influence of different diets on the chemical composition of the femoral gland secretion and suggest caution when interpreting results from captive animals, even in the same species.

Diversity of compounds in femoral secretions of Galápagos iguanas (genera:AmblyrhynchusandConolophus), and their potential role in sexual communication in lek-mating marine iguanas (Amblyrhynchus cristatus)

BackgroundChemical signals are widely used in the animal kingdom, enabling communication in various social contexts, including mate selection and the establishment of dominance. Femoral glands, which produce and release waxy secretions into the environment, are organs of central importance in lizard chemical communication. The Galápagos marine iguana (Amblyrhynchus cristatus) is a squamate reptile with a lek-mating system. Although the lekking behaviour of marine iguanas has been well-studied, their potential for sexual communication via chemical cues has not yet been investigated. Here we describe the diversity of the lipophilic fraction of males’ femoral gland secretions among 11 island populations of marine iguanas, and compare it with the composition of its sister species, the Galápagos land iguana (Conolophus subcristatus). We also conducted behavioural observations in marine iguana territorial males in order to explore the possible function of these substances in the context of male dominance in leks.MethodsFemoral secretions were analysed by gas chromatography coupled to mass spectrometry (GC–MS), and chromatography with a flame ionisation detector (GC-FID) in order to characterise the lipophilic composition. To understand the potential role of femoral secretions in marine iguana intraspecific communication, territorial males were sampled for their femoral glands and monitored to record their head bob rate—a territorial display behaviour in males—as well as the number of females present in their leks.ResultsWe found that the gland secretions were composed of ten saturated and unsaturated carboxylic acids ranging in chain length between C16and C24, as well as three sterols. Cholesterol was the main compound found. Intriguingly, land iguanas have a higher diversity of lipophilic compounds, with structural group of lipids (i.e. aldehydes) entirely absent in marine iguanas; overall the chemical signals of both species were strongly differentiated. Lipid profiles also differed among populations of marine iguanas from different islands, with some islands demonstrating a high diversity of lipophilic compounds (i.e. full spectra of compounds), and others lacking one or more compounds. Among the compounds most frequently found missing were 11- and 13-eicosenoic acids. Gland secretions of males with a better body condition and with a higher dominance status (i.e. those accompanied by females and with higher head bob display) were proportionately richer in C20-unsaturated fatty acids (11-eicosenoic acid).DiscussionLand and marine iguanas strongly diverged in their chemical composition of the femoral glands likely due to ecological differences between both species. Despite that marine iguana populations varied in their femoral gland composition that was not related to their genetic structure. Our results indicated that 11-eicosenoic acid may play an important role in intraspecific chemical communication in marine iguanas.

Skin-derived semiochemicals of the lacertid lizard Acanthodactylus boskianus

Skin lipids impede transcutaneous water loss in several species of squamate reptiles and act as a barrier to harmful microorganisms; they play an additional role as chemical cues involved in chemical communication eliciting behavioral responses in intra- and interspecific interactions. While studies till now give little detailed information on the nature of skin slough, the femoral gland secretions of the lacertid lizardAcanthodactylus boskianushave been analyzed and the chemical profile is known for the species. In the present study we use GC-MS analysis of skin slough to focus on the chemical composition of skin in the xeric-adapted lacertid lizardA. boskianusand compare this to its femoral secretions. In the shed skin we detected steroids, alcohols, carboxylic acids, alkanes, aldehydes, carboxylic acid esters, squalene, monoglycerides of fatty acids, glycerol monoethers of long chain alcohols, and 1,3 alkanediol, which are the same chemical groups already found in the femoral secretions of this species. However, the relative percentages of these compounds in skin slough differ from those known for femoral secretions. While the compounds characterizing skin slough are qualitatively similar to femoral secretions, they could represent an adaptation to hot and dry habitats ofA. boskianus. With regard to the characteristic chemical profiles for different sexes, there is not enough evidence to support their possible role as chemosignals, and behavioral experiments should be performed to test the possible use of skin shedding in intraspecific communication.