oa Lipophilic compounds in femoral gland secretions of spiny-tailed lizard, dhub, Uromastyx aegyptia microlepis (Reptilia, Agamidae) from the Qatar desert

In many lizards, chemical compounds from the femoral gland secretions are used in intraspecific communication, but most studies describing these chemicals are for European lizard species included in the Scleroglossa clade. Lizards within the Iguanian clade have been much less studied, probably because these lizards were considered to rely more on visual cues. However, many iguanian lizards have abundant femoral secretions and are able to exercise chemosensory conspecific recognition, which might be based on compounds secreted by femoral glands. To understand what determines the composition of gland secretions of lizards and their role in social behavior, we need more studies that deal with a wider range of lizard species within different taxonomic groups and to consider a larger variety of environmental conditions. By using gas chromatography-mass spectrometry (GC-MS), we found 85 lipophilic compounds in femoral gland secretion of male and female spiny-tailed lizards, Uromastyx aegyptia microlepis. The type of compounds were similar between sexes, but males had a greater diversity of compounds (n= 80) than females (n= 64), and some specific compounds were exclusive of either males or females, and proportions differed between sexes. Main compounds were 27 steroids (58.6 % in males vs. 83.2 % in females; mainly cholesterol and 4,22-stigmastadiene-3-one), 13 carboxylic acids and some of their esters (16.5 % in males but only 1.5 % in females; mainly hexadecanoic acid), 4 terpenoids (mainly squalene; 9.5 % in males vs 3.6 % in females), 23 waxy esters of fatty acids (6.5 % in males and 6.1 % in females), α-tocopherol (3.4 % in males and 2.1 % in females), ketones (1.6 % in males and 2.0 % in females) and other minor compounds such as aldehydes (0.8 % only in males) and alcohols (0.5 % in males and 0.1 % in females). We compared these compounds with those found in other lizard species and discussed the potential signaling function of some compounds and how the xeric habitat could have conditioned the composition of secretions in order to maximize the efficiency and durability of scent marks in the desert.