Responses of female rock lizards to multiple scent marks of males: Effects of male age, male density and scent over-marking

A novel epidermal gland type in lizards (α-gland): structural organization, histochemistry, protein profile and phylogenetic origins

Chemical signalling is an essential component of the communication system of lizards, and epidermal glands are responsible for producing semiochemicals that regulate many behavioural interactions. Two types of epidermal glands have been previously described for lizards: follicular and generation glands. Generation glands are characterized by the aggregation of novel glandular cell types in the epithelium and the lack of a lumen or external pore. Despite the fact that several subtypes of generation glands have been recognized over the years, the morphology, taxonomic distribution, function and evolutionary origins of generation glands remain nearly unexplored in Neotropical clades. Here, we describe a novel escutcheon-type generation gland (‘α-gland’) for lizards of the South American family Tropiduridae, characterize its structural and ultrastructural organization, and study the homology of the constituent parts in a phylogenetic framework. The α-glands emerged in the ancestor of Eurolophosaurus, Plica, Strobilurus, Tropidurus and Uracentron, and are found in at least 39 species with diverse ecological habits. We preliminarily analysed the protein profile of α-glands and discovered differential expression of protein components between sexes. Our investigations change the general view about epidermal gland homology, leading us to argue that generation and follicular glands are possibly more closely related functionally and evolutionarily than previously thought.

Linking behavioral thermoregulation, boldness, and individual state in male Carpetan rock lizards

Mechanisms affecting consistent interindividual behavioral variation (i.e., animal personality) are of wide scientific interest. In poikilotherms, ambient temperature is one of the most important environmental factors with a direct link to a variety of fitness-related traits. Recent empirical evidence suggests that individual differences in boldness are linked to behavioral thermoregulation strategy in heliothermic species, as individuals are regularly exposed to predators during basking. Here, we tested for links between behavioral thermoregulation strategy, boldness, and individual state in adult males of the high-mountain Carpetan rock lizard (Iberolacerta cyreni). Principal component analysis revealed the following latent links in our data: (i) a positive relationship of activity with relative limb length and color brightness (PC1, 23% variation explained), (ii) a negative relationship of thermoregulatory precision with parasite load and risk-taking (PC2, 20.98% variation explained), and (iii) a negative relationship between preferred body temperature and relative limb length (PC3, 19.23% variation explained). We conclude that differences in boldness and behavioral thermoregulatory strategy could be explained by both stable and labile state variables. The moderate link between behavioral thermoregulatory strategy and risk-taking personality in our system is plausibly the result of differences in reproductive state of individuals or variation in ecological conditions during the breeding season.

Antipredatory behaviour of a mountain lizard towards the chemical cues of its predatory snakes

The ability to early detect a potential predator is essential for survival. The potential of Iberolacerta cyreni lizards to discriminate between chemical cues of their two predatory snakes Coronella austriaca (a non-venomous active-hunter saurophagous specialist) and Vipera latastei (a venomous sit-and-wait generalist) was evaluated herein. A third snake species, Natrix maura, which does not prey on lizards, was used as a pungent control. Thus, the behaviour of I. cyreni was studied regarding four treatments: (1) C. austriaca scent, (2) V. latastei scent, (3) N. maura scent and (4) odourless control. Lizards showed antipredator behaviour (such as slow-motion and tail waving) to C. austriaca and V. latastei chemicals. The antipredatory response was similar for both predators. This ability to react with an intensive behavioural pattern to the chemical cues of their predatory snakes may prevent lizards from being detected, and, if detected, dissuade the predator from beginning a pursuit.

Effects of age on the courtship, copulation, and fecundity of Pardosa pseudoannulata (Araneae: Lycosidae)

According to sexual selection theory, age affects the preference of mate choice, and this preference ultimately influences the fecundity of the female. Pardosa pseudoannulata (Araneae: Lycosidae) is a valued predator in many cropping systems. By determining oviposition rate, egg hatching rate, and also the number and carapace width of the 2nd instar spiderlings of the F₁ generation, we explored the effects of age on fecundity of the female spider. There were no significant effects of age on courtship duration, sexual cannibalism rate, mating rate, oviposition rate, egg hatching rate, or the number and carapace width of 2nd instar spiderings of P. pseudoannulata. However, age had a significant effect on courtship latency, courtship intensity, and mating duration of the spider. Courtship latency decreased significantly with an increase in the age of the male, and courtship intensity of the low-age male increased with increasing female age. Increasing age of male and female spiders was associated with significantly prolonged mating duration. The results indicated that low-age male spiders were more inclined to mate with high-age females, and age had no significant effect on sexual cannibalism rate or the fecundity of the female.

In Space and Time: Territorial Animals are Attracted to Conspecific Chemical Cues

Territorial animals lay scent marks around their territories to broadcast their presence, but these olfactory signals can both attract and repel con-specifics. Attraction or aversion can have a profound impact in terms of space use and thereby influence an individual's access to resources and mates. Here, we test the impact of chemical signals on the long-term space use and activity of receivers, comparing the response of males and females, territory holders, and temporary visitors in Sceloporus undulatus lizards in the field. We placed either male femoral gland secretions (chemical) or blank (control) cues on resident male landmarks, repeatedly over 5 d, while monitoring the activity and location of all lizards in the vicinity. We found that resident males and females, but not non-resident males, were active on more days near landmarks treated with chemical cues than landmarks treated with control cues. Non-resident males remained closer to chemical than control cues. These results suggest that territorial scent marks are attractive to conspecifics and impact space use, but that the specific effects depend on receiver sex and residency status. Such subtle or gradual changes in behavior may frequently be overlooked by short-term choice experiments. Future studies investigating the behavioral significance of a communicative signal should consider these finer details of behavior for a more comprehensive assessment.

Testing the functionality of precloacal secretions from both sexes in the South American lizard, Liolaemus chiliensis

The behavior of lizards can be highly influenced by chemical senses. The most studied pheromonal sources in lizards has been the femoral and precloacal gland secretions, although studies have been focused on male secretions, probably because these glands are usually only present in males or are poorly developed in females when they are present. Here, we aimed to study inLiolaemuschiliensis, one of the fewLiolaemusspecies in which females have precloacal glands, if female precloacal secretions convey information. We recorded the response of both sexes to secretions from females and males, as well as to control (solvent). The lizards started to explore the secretions sooner than the control. Both sexes moved more when exposed to female secretions than to the control, and males, but not females, explored female secretions more than the other scents. These results suggest that volatile compounds of the secretions allow lizards to recognize the presence of conspecifics, and, at least for males, these trigger the exploration of non-volatile compounds of the secretions that may reveal the sex of the individual that deposited them. This is the first study that explores the response to female precloacal secretions inLiolaemus, and data indicate that the female secretions ofL. chiliensiscontain relevant information for social interactions.

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.

Condition-dependent chemosignals in reproductive behavior of lizards

This article is part of a Special Issue "Chemosignals and Reproduction". Many lizards have diverse glands that produce chemosignals used in intraspecific communication and that can have reproductive consequences. For example, information in chemosignals of male lizards can be used in intrasexual competition to identify and assess the fighting potential or dominance status of rival males either indirectly through territorial scent-marks or during agonistic encounters. Moreover, females of several lizard species "prefer" to establish or spend more time on areas scent-marked by males with compounds signaling a better health or body condition or a higher genetic compatibility, which can have consequences for their mating success and inter-sexual selection processes. We review here recent studies that suggest that the information content of chemosignals of lizards may be reliable because several physiological and endocrine processes would regulate the proportions of chemical compounds available for gland secretions. Because chemosignals are produced by the organism or come from the diet, they should reflect physiological changes, such as different hormonal levels (e.g. testosterone or corticosterone) or different health states (e.g. parasitic infections, immune response), and reflect the quality of the diet of an individual. More importantly, some compounds that may function as chemosignals also have other important functions in the organism (e.g. as antioxidants or regulating the immune system), so there could be trade-offs between allocating these compounds to attending physiological needs or to produce costly sexual "chemical ornaments". All these factors may contribute to maintain chemosignals as condition-dependent sexual signals, which can inform conspecifics on the characteristics and state of the sender and allow making behavioral decisions with reproductive consequences. To understand the evolution of chemical secretions of lizards as sexual signals and their relevance in reproduction, future studies should examine what information the signals are carrying, the physiological processes that can maintain the reliability of the message and how diverse behavioral responses to chemosignals may influence reproductive success.

Do poison frogs recognize chemical cues of the other sex or do they react to cues of stressed conspecifics?

Although anuran communication primarily takes place acoustically, chemical cues are also often used for intra- and intersexual communication in frogs. In the present study we analyzed the behavior of the poison frog Ranitomeya variabilis when presented chemical cues of same-sex or opposite-sex conspecifics. Chemical cues were obtained by keeping a single frog on a moist paper towel for about 47h. Afterwards two paper towels were offered to a test animal, one containing the chemical cues, the other containing rainwater only. We ran trials presenting female cues to males, males cues to males as well as male cues to females. The results of the trials were not significant in terms of intersexual communication. The overall response revealed a clear avoidance strategy which leads us to the assumption that disturbance cues unintentionally occurred during the experiment. The rather small size of the containers used to obtain chemical cues prior to the trials probably lead to confinement stress which consequently caused increased urination containing stress hormones that were detected by the test animals. This is the first proof of disturbance cues and their effects in adult anurans. The results of this study do not allow conclusions about inter- or intrasexual chemical communication of R. variabilis, but they allow implications and revisions for future experiments on this topic.