Pilar López

Amphisbaenia is a group of burrowing fossorial reptiles that uses their heads as the primary tool for digging. The shape of their skulls is influenced by the mechanical needs of the animal, such as digging and feeding. Four basic skull shapes are recognized: rounded, keeled, shovel‐shaped, and spade‐shaped. Trogonophis wiegmanni is an Amphisbaenia that is the only round‐headed representative among Trogonophidae. The species occurs in the Maghreb region in the arid Mediterranean biome. We analyzed the skull and mandible of this species using 3D Geometric Morphometrics (3D‐GMM), a technique that uses Cartesian coordinates of homologous landmarks to analyze and compare shape variations through robust statistical methods, enabling separate analysis of size and shape components. Our hypothesis is that the ontogenetic variation present in T. wiegmanni development would follow the general pattern found in other amphisbaenians. We analyzed the cranial morphological variations in an ontogenetic series of T. wiegmanni using 3D‐GMM. We examined computed tomographic scans of 11 specimens (7 juveniles and 4 adults). For this, 16 landmarks were placed on the left side of the skull, covering the dorsal, lateral, and ventral surfaces, and 18 other landmarks were placed on the labial and lingual views of the mandible. The landmarks were selected for their ontogenetic stability, meaning they could be identified in both juvenile and adult individuals. Principal components and regression analyses between shape (dependent variable) and size (independent variable) showed clear differences between the cranial morphological patterns of juveniles and adults. For instance, juveniles tend to have a wider intermediate segment, a subtle sagittal crest, and little bone fusion, with evident sutures. As in other Amphisbaenia species with different skull morphotypes, the variation was strongly correlated with the size change from juvenile to adult, indicating a dominant role for ontogenetic allometry in determining skull and mandible shapes. Therefore, at least for the skull, this appears to be a common ontogenetic pattern for skull morphology of Amphisbaenia.

Parasites impact host fitness and constitute an important selective pressure on the host's life history. According to parasite‐mediated sexual selection, ornaments are presumed to honestly indicate immune capacity or resistance against parasites, and the chooser sex (typically females) obtains an advantage by selecting more ornamented, thus more immunocompetent mates. Therefore, signalers mounting an immune response must allocate resources from the sexual signal to the immune system, hence reducing the expression of the ornament and becoming less attractive to the choosing sex. Here, we test this idea in the lizard Psammodromus algirus. We inoculated a subsample of males with lipopolysaccharide (LPS) of the cell wall of Escherichia coli, while others served as sham controls. The inoculation of LPS decreased the proportion of ergosterol (pro‐vitamin D₂) in femoral secretions, and chemosensory tests showed that the scent of LPS‐inoculated males was less attractive to females than the scent of control males. Given that ergosterol is a precursor of vitamin D, which has physiological functions as an immune modulator, immunocompromised males likely needed to divert vitamin D to the immune system, reducing the allocation of ergosterol to secretions. In this way, females could detect “sick” males, preferring the apparently healthy males. Overall, our study shows that mounting an immune response is costly in terms of reduced attractiveness. Moreover, we disentangle the underlying mechanism, which involves an honest signal based on vitamin D allocation.

Chemosensory communication in lizards may be based on multiple compounds coming from multiple sources. Both secretions from external epidermal glands, and internal cloacal glands and feces are known to convey information (sex, familiarity, body size, etc.) for conspecifics. However, although some compounds in femoral gland secretions have been characterized and their function examined, there is very little information on potential semiochemicals in cloacal products and feces. More importantly, it is not well-known whether the compounds and information from multiple sources are redundant, complementary, or different. We analyzed the lipids in femoral gland secretions and feces of male Carpetan rock lizards (Iberolacerta cyreni) and examined which compounds might predict body size. We found many compounds in feces, mainly steroids, alkanes, and branched alkanes, while the main compounds in femoral secretions were steroids and fatty acids. The body size of males was related to the proportions of some alkanes, alkenes, and terpenoids in feces, while it is related to the proportions of some steroids and fatty acids in femoral secretions. There were also differences in the chemical profiles of feces of males and females, which may allow sex recognition. Therefore, femoral secretions and feces may both inform on males’ sex and body size, but the chemical bases of this information are different depending on the source.

Background: Many animals rely on chemical cues for intraspecific communication. This is especially important in fossorial animals because visual restrictions of the underground environment limit the opportunities for visual communication. Previous experiments showed the ability of the amphisbaenian Trogonophis wiegmanni to discriminate between several categories of conspecifics based on chemical cues alone. However, in contrast with many other reptile species, T. wiegmanni does not have external secretory glands, but uses uncharacterized secretions from the cloaca in intraspecific chemosensory communication. Methods: Using gas chromatography-mass spectrometry (GC-MS), we analyzed the lipophilic compounds from feces and cloacal products freshly extracted from the cloaca of male and female T. wiegmanni. We identified and estimated relative proportions of the compounds found, and tested for intersexual and body-size related differences. Results: We found a total of 103 compounds, being some steroids (mainly cholesterol and cholestanol), some alkanes and squalene the most abundant and frequent. Further, we found intersexual differences, with males, especially larger ones, having higher proportions of several alkanes between C₁₃ and C₂₄ and of squalene than females, which had higher proportions of several steroids and also of nonacosane and methylnonacosane than males. We compared these findings with secretions of other animals and discuss the potential role of these compounds and their variations in intraspecific communication of amphisbaenians.

Dichlorodiphenyltrichloroethane (DDT) is a pesticide that was commonly used for decades worldwide. The use of DDT was banned in the 1970s and 1980s in Europe because of its high toxicity and persistence in the environment, bioaccumulation in living organisms and biomagnification through food webs. However, monitoring using both invasive and non‐invasive methods has routinely reported the occurrence of DDT metabolites such as dichlorodiphenyldichloroethylene (DDE) in wild birds, providing valuable information about the exposure to pesticides and potential differences between species and over time. Here, we analysed the relative proportion of DDE in the uropygial gland secretions of European Blackbirds Turdus merula from two localities in southern Spain. Given the negative effects of this pollutant on animal immunity, we also tested for associations between the prevalence of haemosporidians and the relative proportion of DDE in their secretions. Relative proportions of DDE varied between sampling sites and were higher in females than in males, regardless of their age. In spite of the potential immunosuppressive effect of DDE, haemosporidian infection was not associated with DDE presence.

The uropygial gland of birds produces an oily secretion with different functions, mainly related to plumage protection. In addition, the volatile compounds of this secretion may act as chemical signals that provide information to conspecifics, but it is also possible that those compounds may further attract hematophagous insect vectors such as those responsible for avian malaria transmission. Individual characteristics such as sex and age are usually associated with variation in the composition of the uropygial secretion. Different studies have shown that mosquitoes are more attracted towards birds infected by avian malaria parasites. However, whether the individual infection status by these parasites may lead to differences in the composition of this secretion remains poorly known. We used gas chromatography–mass spectrometry (GC–MS) to characterise the chemical composition of the volatile lipophilic fraction of the uropygial gland secretions of wild European blackbirds and compare its composition in an urban and a forest locality according to their age, sex and infection status by blood parasites. We found differences in the composition of the secretion between age classes and also between sexes within adult birds. However, no differences were found in the chemical composition of the uropygial gland secretion of birds according to their infection status by blood‐parasites and habitat type. These results suggest that haemosporidian infection does not alter the composition of the volatile fraction of uropygial gland secretions in infected birds.

Chemical communication plays an essential role in several social and reproductive behaviors of many animals. In lizards, the main sources of semiochemicals are femoral or pre‐anal gland secretions and feces. In male lizards Psammodromus algirus, there are age‐related differences in the chemical composition of femoral gland secretions and in the reproductive strategies, with older males defending territories and females, while younger males adopting sneak‐mating strategies. Females flee more often from mating advances of young males than from those of old males, which are more successful in obtaining matings. This suggests that age discrimination of males may be important for females. We tested here whether females showed differential chemosensory responses to chemical cues (femoral gland secretion and feces) of males of two age classes, and whether females use information from substrate scent marks of males of different ages to select where to stay. We found that females elicited more tongue‐flicks to the secretion and feces of old males than to control or secretion and feces of young males. Also, the time spent by females on a scented paper depended on the treatment, suggesting that females tended to spend more time on scent marks made with femoral secretions of old males. Adult females seemed capable to discriminate between young and old males based on chemical cues alone and showed more interest in scents of old males. However, substrate scent marks did not seem to entirely determine site selection by females, suggesting that females might need additional cues to perform the choice. These results can be explained by the different age‐dependent reproductive strategies of males, which can affect differentially to females.

Female Carpetan rock lizards (Iberolacerta cyreni) might assess the quality of males from their chemical signals. Females select areas scent marked by males with secretions containing high proportions of provitamin D to ensure mating with high-quality males. However, an alternative explanation might be that females are not choosing a mate, but that females have a pre-sensory bias for chemical cues of vitamin D in the food and are, in fact, assessing habitat quality to obtain direct benefits of increasing the intake of vitamin D. We evaluated experimentally the possible benefits of a nutritional supplement of provitamin D or vitamin D in pregnant females for their clutches and offspring. However, we did not find large differences between treatments, except in the lower body condition of juveniles of mothers supplemented with provitamin D. We also tested the chemosensory interest of females in the scent of males to study the existence of a sensory bias; this response decreased when the amount of dietary vitamin D exceeded their needs. The results suggest that there are no reproductive benefits in the intake of additional vitamin D and that the potential sensory bias to scents of males could be related to the physiological needs of the females.