Acanthodactylus Boskianus Research Articles

Movement and space use in three sympatric lacertid lizards (Acanthodactylus): Inter‐ and intraspecific comparisons

AbstractCompetition can be keen within and between closely related species but can be reduced when sympatric individuals differ in resource use. To determine how sympatric, closely related species coexist, we examined movement and activity of foraging individuals, developing detailed profiles for males of three species (Acanthodactylus boskianus, A. dumerilii and A. scutellatus) and for female A. boskianus in arid sub‐desert steppes of southern Tunisia. All three species were active concurrently with different peak activity times. Males varied markedly in their movement, as did A. boskianus sexes. Interspecifically, male A. boskianus moved most frequently, for the most time, covering the greatest distance and searching the largest area, while male A. dumerilii moved the least often, travelled the shortest distances and intensively searched small areas. Acanthodactylus scutellatus males generally were intermediate between the other species but dug more frequently and had movement rates comparable to A. boskianus. Intraspecifically, A. boskianus females moved less frequently, for a smaller percentage of time, covering shorter distances and searching smaller areas than male A. boskianus. Habitat use varied among species and by sex within A. boskianus. Differences in movement and activity likely reflect differences in resource use that promote coexistence between and within species.

Регистрация зимней активности у двух видов ящериц в Египте

Two Acanthodactylus boskianus and three Mesalina guttulata were recorded on the surface at day time, 12 January 2022 in the South Eastern Desert, Red Sea Governorate, Egypt. The weather was clear full day, in the middle of the day the air temperature reached +24⁰C. Lizards not only actively moved, but also demonstrated foraging behavior. This is the first documented record of winter activity of lacertids in Egypt.

Behavioral fever in Bosk's fringe-toed lizards (Acanthodactylus boskianus) living in an industrial area in south-eastern Tunisia.

As an indicator of physiological state of lizards, thermoregulatory behavior has been proposed as an assessment tool of environmental contamination, particularly in desert ecosystems where lizards represent a major biological component. Although pesticide contamination has been shown to induce behavioral fever in lizards, the possible pyrogenic effect of heavy metals has received less attention. The objective of this study was to provide data on this issue by using Bosk's fringe-toed lizards (Acanthodactylus boskianus) living in a metal-contaminated industrial area in south-eastern Tunisia as a study model. Combining field observations of behavior with measures of thermoregulatory performance under laboratory conditions, we found that proximity to the industrial zone was associated to a different thermoregulatory behavior of lizards. There was a tendency of lizards living close to the contamination source to display behavioral fever, as they spent more time in the sun, preferred higher body temperatures, and warmed up faster, compared to lizards living far away. This heat-seeking behavior is likely a reaction to improve the functioning of physiological systems involved in the defense against toxic effects of heavy metals, possibly through the increase of metabolic rate, stimulation of enzymes involved in the detoxification process, and enhancement of immune defense systems. Our findings stress the need for further detailed studies into the physiological mechanisms linking metal contamination to behavioral fever. They also underline the usefulness of thermoregulatory behavior as a reliable, non-destructive, and inexpensive, individual-level biomarker in lizard ecotoxicology and biomonitoring of contaminated desert environments.

A new species of Acanthodactylus Fitzinger, 1834 (Sauria: Lacertidae) from the Zagros Mountains, Iran.

Acanthodactylus boskianus is a widespread species in Northern Africa and Western Asia. In this study, we used morphological and genetic approaches to study populations of A. boskianus from the Zagros Mountains in western Iran, the easternmost limit of the species distribution. Our morphological and genetic data indicate that populations of A. boskianus in Iran are distinct from other populations of A. boskianus. Therefore, we describe the Iranian populations as Acanthodactylus zagrosicus sp. nov. The new species is the third endemic species of Acanthodactylus in Iran and the ninth Acanthodactylus species distributed in Iran overall. According to our surveys, this species is distributed widely in the Zagros Mountains including Kermanshah, Lorestan, Ilam, and Khuzestan Provinces.

Ultrastructural comparison between the tongue of two reptilian species endemic in Egyptian fauna; Bosc's fringe-toed lizard Acanthodactylus boskianus and Sinai fan-fingered gecko Ptyodactylus guttatus.

The current observations focused on the ultrastructure comparison between the tongue of two reptile species endemic the Egyptian fauna; Bosc's fringe-toed lizard Acanthodactylus boskianus and Sinai fan-fingered gecko Ptyodactylus guttatus to exhibit the relationship between the lingual epithelium and its function according to their specific feeding strategy. A. boskianus possessed triangular elongated tongue with bifurcated tapering apex and wide base while; the P. guttatus had a triangular flattened tongue with conical shallow bifurcated apex and broad base. The ventral surface of the lingual apex of A. boskianus had transverse while in P. guttatus had two oval pads and median ventral groove. Both surfaces of the tongue of both examined species are covered by stratified squamous epithelium with great variability of degree of keratinization. The dorsal epithelium formed flattened and conical filiform papillae in A. boskianus, while in P. guttatus formed cylindrical papillae, conical, and tall filiform ones. Few taste buds are observed on the fore-tongue but increase on the mid-tongue of A. boskianus, while in P. guttatus, numerous taste buds are distributed on the fore-tongue and mid-tongue. Both surfaces of the laryngeal mound of both examined species provided with numerous of cilia and orifices of laryngeal gland. The present results confirmed that the tongue of A. boskianus acts as a chemoreceptor organ to follow pheromone trails of prey and mates. While in P. guttatus the tongue may play an important role in the feeding mechanism and act as a chemoreceptor organ.

Decreased Cell-Mediated Immune Response in Bosk's Fringe-Toed Lizards (Acanthodactylus boskianus) Inhabiting an Industrialized Area in Southern Tunisia.

Lizards increasingly are recognized as suitable contaminant biomonitors in terrestrial ecosystems. Previously, we have shown that Bosk's fringe-toed lizards (Acanthodactylus boskianus) living close to the Gabès-Ghannouche industrial complex for fertilizer and acid production in southern Tunisia were contaminated by heavy metals. However, the impact of this contamination on lizard health parameters has not been investigated. In this study, we used the phytohaemagglutinin (PHA) skin-swelling test to assess whether the proximity to the industrial complex was associated with notable changes in lizard cell-mediated immune response (CMI). Our results showed significantly lower CMI in lizards living close to the industrial complex compared to those occurring farther away in a similar coastal habitat. Overall, our findings are consistent with the idea of immunotoxic effects of metal contamination. They also stress the usefulness of the PHA approach as an efficient tool for the evaluation of contaminant-related immunosuppression in lizards.

Small vertebrates running on uneven terrain: a biomechanical study of two differently specialised lacertid lizards

While running, small animals frequently encounter large terrain variations relative to their body size, therefore, terrain variations impose important functional demands on small animals. Nonetheless, we have previously observed in lizards that running specialists can maintain a surprisingly good running performance on very uneven terrains. The relatively large terrain variations are offset by their capacity for leg adjustability that ensures a ‘smooth ride’ of the centre of mass (CoM). The question as to how the effect of an uneven terrain on running performance and locomotor costs differs between species exhibiting diverse body build and locomotor specializations remains. We hypothesise that specialized runners with long hind limbs can cross uneven terrain more efficiently than specialized climbers with a dorso-ventrally flattened body and equally short fore and hind limbs. This study reports 3D kinematics using high-speed videos (325 Hz) to investigate leg adjustability and CoM movements in two lacertid lizards (Acanthodactylus boskianus, running specialist; Podarcis muralis, climbing specialist). We investigated these parameters while the animals were running on a level surface and over a custom-made uneven terrain. We analysed the CoM dynamics, we evaluated the fluctuations of the positive and negative mechanical energy, and we estimated the overall cost of transport. Firstly, the results reveal that the climbers ran at lower speeds on flat level terrain but had the same cost of transport as the runners. Secondly, contrary to the running specialists, the speed was lower and the energy expenditure higher in the climbing specialists while running on uneven terrain. While leg movements adjust to the substrates’ variations and enhance the stability of the CoM in the running specialist, this is not the case in the climbing specialist. Although their legs are kept more extended, the amplitude of movement does not change, resulting in an increase of the movement of the CoM and a decrease in locomotor efficiency. These results are discussed in light of the respective (micro-)habitat of these species and suggest that energy economy can also be an important factor for small vertebrates.

Observation resolution critically influences movement-based foraging indices

Movement‐based indices such as moves per minute (MPM) and proportion time moving (PTM) are common methodologies to quantify foraging behavior. Hundreds of studies have reported these indices, many without specifying the temporal resolution of their original data, and others using varying resolutions. This was done despite the likelihood that observation resolution can affect MPM and PTM estimates. Our goal was to empirically determine the sensitivity of these foraging indices to changes in the temporal resolution of the observation. We used a high-speed camera to record movement sequences of 20 Acanthodactylus boskianus lizards. Then, we gradually decreased the resolution of the data and calculated the foraging indices at different temporal resolutions. When considering the range of temporal resolutions that are relevant for field observations with unassisted vision, we found 68% and 48% difference in MPM and PTM estimates, respectively. When using the highest resolution, our estimate of MPM was an order of magnitude higher than all prior reported values for lizards. Our results raise major concerns regarding the use of already published movement-based indices, and enable us to recommend how new foraging data should be collected.

Gastrointestinal helminths of lizards (Reptilia: Squamata) from Egypt

Background: Despite the fact that Egypt contains a large number of lizard species, yet there is little knowledge recorded regarding the helminth fauna infecting this group of hosts. A parasitological study on gastrointestinal helminths of lizards was carried out during Summer (August) and Autumn (September and October), 2014 and 2015, respectively. Objective: This study aims to update information on helminth parasites that infect lizards in Egypt. Material and Methods: Seven species of lizards, Pseudotrapelus sinaitus Heyden, 1827; Trapelus mutabilis Merrem, 1820 (Agamidae); Tarentola mauritanica mauritanica Linnaeus, 1758 (Phyllodactylidae); Tropiocolotes tripolitanus Peters, 1880 (Gekkonidae); Acanthodactylus boskianus Daudin, 1802 (Lacertidae); Chamaeleo africanus Laurenti, 1768 (Chamaeleonidae); and Varanus niloticus Linnaeus, 1766 (Varanidae), were collected from several parts of Egypt. These hosts were dissected and examined for gastrointestinal helminth. The collected helminths were fixed in 70% ethanol, stained with carmine and examined by using an Olympus CX31 microscope and a Zeiss Stemi 2000-C microscope. Results: The total prevalence of infection with helminths was 35.9%. The study recorded 16 species of helminths recognised as: six species of digenea [Prosthodendrium obtusum (Looss, 1896) Bhalerao, 1936, Pleurogenoides tener (Olsson, 1876) Travassos, 1921, Anchitrema sanguineum (Sonsino, 1894) Looss, 1899, Cyclorchis varani Price, 1936, Mesostephanus milvi Yamaguti, 1939 and Haplorchis pumilio (Looss, 1896) Looss, 1899], four species of cestodes [three adults, Oochostrica mutabili Morsyet al., 2013, Duthiersia fimbriata Diesing, 1854 and one unidentified cestode and one tetrathyridia of Mesocestoides spp.] and six species of nematodes [Parapharyngodon micipsae Seurat, 1917, Pharyngodon inermicauda Baylis, 1923, Abbreviata leptosome Gervais, 1848, Thubunaea pudica Seurat, 1914, Tanqua tiara (von Linstow, 1879) Blanchard, 1904 and Spinicauda sonsinoi (Linstow, 1894) Travassos, 1920]. Conclusion: This study documents 10 new host and 10 new locality records in Egypt and distinguishes between studied material and reported descriptions. These findings add significantly to the present information on helminths infecting lizards in Egypt.

Comparative anatomical study of the hyoid apparatus of Bosk\u2019s fringe-toed lizard and spotted fan-toed gecko (Squamata: Lacertidae and Phyllodactylidae)

BackgroundThe present study aimed to illustrate comparative morphological, histological, and functional variations of the hyoid apparatus of Acanthodactylus boskianus and Ptyodactylus guttatus.ResultThe hyoid apparatuses and musculature of the two investigated species are well-developed. The hyoid apparatuses exhibit high mobility with different articulation sites between their skeletal elements. The degree of ossification of the hyoid apparatus of gecko is more developed than that of the lacertid lizard. In P. guttatus, a well-developed synchondrosis articulation appears between the basihyoid and ceratobranchialis of the hyoid apparatus. Meanwhile, in A. boskianus, the articular ligament which appears between basihyoid and ceratobranchialis is less developed and also appears as a ligament connection between the two parts of hyoid cornua in which ligaments provide more mobility to the hyoid of lacertid lizard.ConclusionThe results reflect a phylogenetically informative character about these clad and explain the different functional demands imposed on the hyoid apparatus as well as confirm the important role of hyoid apparatus in the movement of the tongue during the prey transport.

Microscopically Studies on the Liver of Acanthodactylus boskianus lizard

The aim of this study was to investigate the histological and fine structure of the liver of Acanthodactylus boskianus during the hibernation period, using ten adult specimens captured from sandy areas of Aswan Governorate, Egypt. Specimens of liver were fixed for light and transmission electron microscope to study the hepatic architecture during this period. In addition to haematoxylin and eosin stain, the histochemical and special stains were used. The hepatocytes are arranged in hepatic plates. The radial arrangement of hepatic cords around the central vein is generally not apparent. The several-cell-thick plate type showed with multi-layered of hepatocytes separated by narrow tortuous capillaries networks, sinusoids that are localized in the space between hepatic plates. The hepatic cells of Acanthodactylus boskianus under light and T.E.M. are similar to those of other vertebrates (birds and mammals), except for the presence of melano- macrophages.

Compliant legs enable lizards to maintain high running speeds on complex terrains

Substrate variations are likely to constrain animal performance in natural environments, as running over complex terrains challenges the dynamic stability of the body differently in each step. Yet, being able to negotiate complex terrains at top speed is a strong advantage for animals that have to deal with predators and evasive prey. Little is known on how animals negotiate such terrain variability at high speed. We investigated this in fast-running Acanthodactylus boskianus lizards, by measuring their 3D kinematics using four synchronised high-speed video cameras (325 Hz) on an adaptable racetrack. This racetrack was covered with four different substrates, representing increasing levels of terrain complexity. We found that the lizards deal with this complexity gradient by gradually adopting more erect parasagittal leg postures. Legs in a more-erect position are more compliant and are therefore highly adjustable on complex terrains. Additionally, the lizards stabilise their head, which facilitates vestibular and visual perception. Together, compliant legs and head stabilisation enable the lizards to minimise movements of the body centre of mass, even when running on highly irregular terrains. This suggests that the head and the centre of mass are the priority targets for running on uneven terrains. As a result, running performance (mean forward speed) decreases only slightly, and only on the most challenging substrate under investigation.

Comparative and functional study of integumentary system of two different reptiles: adaptation to their different modes of life

Aim of the work: the present study aimed to illustrate the structure and function of the integumentary system of two reptile''s species (Bosc’s fringe toed-lizard (Acanthodactylus boskianus, A. boskianus)and spotted fan-fingered gecko (Ptyodactylus guttatus , P. guttatus) and discussed the influence of different behaviors on their structure (keratinzation and pigmentation, claws, adhesion pads and sensory hairlets). Material and methods: the present study used light and scanning electron microscopy to investigate the structure of skin layers of A. boskianus and P. guttatus. Results: the thin epidermal layer of Acanthodactylus boskianus was covered by hard keratinized horny epidermal scales, while the epidermal layer of Ptyodactylus guttatus was well distinguished and covered by soft keratinized layer. Moreover, in P. guttatus the scales were non-overlapping along the whole length of the body with dome-like shaped on head region, while in A. boskianus the scales were overlapping and articulating with each other by thin hinge. In the present study the dermis of A. boskianus, was the deeper layer of collagenous connective tissue with a rich supply of blood vessels and nerves, while, the dermis of P. guttatus was formed of both collagenous and adipose tissues. Three types of chromatophores (melanophores, iridophores and xanthophores) were distinguished in the skin of both studied species. In A. boskianus, the melanophores were black, large and have dendrites invaginates in the stratum basale of epidermis. The iridophores (reflecting pigments) were scattered in the dermis with large number in the ventral skin than the dorsal one. In P. guttatus, melanphores they were larger, blackish brown and scattered within dermis beneath the iridophores with less number in P. guttatus than that of A. boskianus. Xanthophores (absorbing pigment) were more prominent in P. guttatus than that of A. boskianus. Conclusion: examination of the skin of the two studied reptile species revealed great variations in distributionof chromatophoresthrough the whole bodyreflecting the adaptation of each animal to different modes of life.

Comparative and functional study of integumentary system of two different reptiles: adaptation to their different modes of life

Aim of the work: the present study aimed to illustrate the structure and function of the integumentary system of two reptile''s species (Bosc’s fringe toed-lizard (Acanthodactylus boskianus, A. boskianus)and spotted fan-fingered gecko (Ptyodactylus guttatus , P. guttatus) and discussed the influence of different behaviors on their structure (keratinzation and pigmentation, claws, adhesion pads and sensory hairlets). Material and methods: the present study used light and scanning electron microscopy to investigate the structure of skin layers of A. boskianus and P. guttatus. Results: the thin epidermal layer of Acanthodactylus boskianus was covered by hard keratinized horny epidermal scales, while the epidermal layer of Ptyodactylus guttatus was well distinguished and covered by soft keratinized layer. Moreover, in P. guttatus the scales were non-overlapping along the whole length of the body with dome-like shaped on head region, while in A. boskianus the scales were overlapping and articulating with each other by thin hinge. In the present study the dermis of A. boskianus, was the deeper layer of collagenous connective tissue with a rich supply of blood vessels and nerves, while, the dermis of P. guttatus was formed of both collagenous and adipose tissues. Three types of chromatophores (melanophores, iridophores and xanthophores) were distinguished in the skin of both studied species. In A. boskianus, the melanophores were black, large and have dendrites invaginates in the stratum basale of epidermis. The iridophores (reflecting pigments) were scattered in the dermis with large number in the ventral skin than the dorsal one. In P. guttatus, melanphores they were larger, blackish brown and scattered within dermis beneath the iridophores with less number in P. guttatus than that of A. boskianus. Xanthophores (absorbing pigment) were more prominent in P. guttatus than that of A. boskianus. Conclusion: examination of the skin of the two studied reptile species revealed great variations in distributionof chromatophoresthrough the whole bodyreflecting the adaptation of each animal to different modes of life.

Comparative Functional Analysis of the Anatomy of the appendicular skeleton in two reptilian species

Aim of the work: the present study aimed to illustrate the osteological characters of the appendicular skeleton of two Egyptian lizard species, Acanthodactylus boskianus and Ptyodactylus guttatus and clarify the relationship between characteristics of the appendicular skeleton and mode of their locomotion of the two species. A. boskianus is diurnal insectivorous lizard forage in open area and it is a generalized ground-dwelling species and P. guttatus is a diurno-nocturnal omnivorous gecko which is a highly specialized climbing on vertical substrates. Material and methods: in the present study we used Alizarin red and Alcian blue as double skeletal staining to investigate the the bony and cartilaginous pattern of limbs and girdles of A. boskianus and P. guttatus. Results: in P. guttatus, the pectoral girdle was characterized by the presence of the interclavicles was dagger in shape and partially fused with clavicles, while it was cruciform and completely fused with the clavicles in A. boskianus. In P. guttatus, the epicoraoid was well developed, broad bony plates and fused with the interclavicles, while in A. boskianus it was narrow cartilaginous, plates and overlap in the mid-line. Moreover, in P. gutattus two fenestrae were appeared within coracoid and scapula with un-fenestrated cartilaginous sternum, while one fenestra appeared in both coracoid and sternum of A. boskianus. On other hand, the pelvic girdle of P. guttatus had complete fusions between the pubis, ischium and ilium, while in A. boskianus the pubis articulated poster-omedially with the ischium. In both P. gutattus and A. boskianus, the forelimbs posture was in horizontal plane, while the hind limbs were in vertical plane. In P. gutattus both the fore and hind limbs were relatively equal in length, while the fore limb in A. boskianus was greatly shorter than the hind limb. Conclusion: the P. gutattus is considered as a one of climbers species which have stout appendicular skeleton to support the climbing process on the vertical surface with relatively short limbs, while A. Boskianus is ground-dwellers and also good climbers and use their claws to walk and climbing on rocky areas and these abilities of locomotion depend on the flexibility of skeletal elements of its appendicular skeleton.

Comparative Functional Analysis of the Anatomy of the appendicular skeleton in two reptilian species

Aim of the work: the present study aimed to illustrate the osteological characters of the appendicular skeleton of two Egyptian lizard species, Acanthodactylus boskianus and Ptyodactylus guttatus and clarify the relationship between characteristics of the appendicular skeleton and mode of their locomotion of the two species. A. boskianus is diurnal insectivorous lizard forage in open area and it is a generalized ground-dwelling species and P. guttatus is a diurno-nocturnal omnivorous gecko which is a highly specialized climbing on vertical substrates. Material and methods: in the present study we used Alizarin red and Alcian blue as double skeletal staining to investigate the the bony and cartilaginous pattern of limbs and girdles of A. boskianus and P. guttatus. Results: in P. guttatus, the pectoral girdle was characterized by the presence of the interclavicles was dagger in shape and partially fused with clavicles, while it was cruciform and completely fused with the clavicles in A. boskianus. In P. guttatus, the epicoraoid was well developed, broad bony plates and fused with the interclavicles, while in A. boskianus it was narrow cartilaginous, plates and overlap in the mid-line. Moreover, in P. gutattus two fenestrae were appeared within coracoid and scapula with un-fenestrated cartilaginous sternum, while one fenestra appeared in both coracoid and sternum of A. boskianus. On other hand, the pelvic girdle of P. guttatus had complete fusions between the pubis, ischium and ilium, while in A. boskianus the pubis articulated poster-omedially with the ischium. In both P. gutattus and A. boskianus, the forelimbs posture was in horizontal plane, while the hind limbs were in vertical plane. In P. gutattus both the fore and hind limbs were relatively equal in length, while the fore limb in A. boskianus was greatly shorter than the hind limb. Conclusion: the P. gutattus is considered as a one of climbers species which have stout appendicular skeleton to support the climbing process on the vertical surface with relatively short limbs, while A. Boskianus is ground-dwellers and also good climbers and use their claws to walk and climbing on rocky areas and these abilities of locomotion depend on the flexibility of skeletal elements of its appendicular skeleton.

Reliable proxies for glandular secretion production in lacertid lizards

The epidermal glands of lizards are considered an important source of semiochemicals involved in lizard communication. Many features of the lizard epidermal gland system vary among and within species (e.g. gland number, size, and shape), and some are believed to reflect the degree of intra- and interspecific variation in glandular secretion production, and by extension, the chemical signalling investment of lizards. Traditionally, herpetologists estimate secretion production based on the number of glands or the size of the glands, rather than quantifying the amount of secretion produced. Still, the reliability of these proxies for secretion production has never been validated. Here, I explored the relationship among secretion production (in mass), pore size (surface area, diameter), and gland number in three species of lacertid lizards ( Acanthodactylus boskianus , Timon lepidus , Holaspis guentheri ), and tested which proxies predicted secretion production variation best, and examined whether the same trend is true for all species. The findings of this study show that the total secretion production of lacertids is highly variable among and within species. Variation in secretion production among-species (but not within-species) could partly be explained by variation in body size. While both measures of pore size were positively related with secretion production, my tests revealed the model with only pore diameter as contributing variable explaining absolute secretion production variation (both within and across species) as the best one. Although gland number appeared a suboptimal estimate for secretion production in the three lacertids under study, only family-wide, multi-species comparative tests counting large within-species sample sizes can provide further insight on the matter.

Tail conspicuousness and antipredatory behaviour in Bosk’s fringe-toed lizard (Acanthodactylus boskianus)

Many lizard species show ontogenetic changes in tail colour that are coupled with changes in the antipredatory strategy. However, the ecological factors that influence the relationships between age, tail colour and antipredatory strategy remain poorly understood. In this work, we investigated how antipredatory behaviours vary according to age in Bosk’s fringe-toed lizard (Acanthodactylus boskianus), a species that shows ontogenetic changes in tail colour. First, we verified whether tail conspicuousness increases the probability of predatory attacks, by using two types of plasticine models made to mimic juveniles (red-tailed models) and adults (beige-tailed models) and distributed in a study plot where an avian predator is abundant. We found that juvenile-like red tails were more frequently attacked by predators than the less conspicuous adult-like ones. We also conducted predation simulation experiments on active lizards of different ages and compared their risk-taking and escape behaviours. Adults occurred close to potential refuges (i.e. bushes), while juveniles were more commonly observed in open microhabitats. When approached by the observer, adults rarely conducted tail displays and usually fled in a non-stop way to penetrate inside the nearest bush. However, juveniles conducted tail displays and never fled directly inside a bush. They usually stopped near the target bush and tolerated a closer approach from the observer before making the decision to take refuge inside the bush. It seems that juveniles feared the attacks of adults and avoided entering bushes occupied by adults. Repeated observations of adults acting aggressively towards juveniles provide support for this hypothesis. Overall, our findings highlight the role of tail conspicuousness in the diversion of predatory attacks from the vital parts of the body in the juveniles of Bosk’s fringe-toed lizard. They also suggest that agonistic interactions between adults and juveniles play important roles in shaping their antipredatory behaviour.

Patterns of alpha diversity among Tunisian lizards (Lacertidae)

Reptiles are a successful group in subtropical arid regions. However, little is known about the drivers that influence the diversity of arid reptile communities. One approach is to investigate the variation in phylogenetic structure of the communities along a broad environmental gradient. In this study, I investigated these patterns in the communities of lacertids at the periphery of the Sahara Desert in Tunisia. The effect of the environment was assessed based on a set of variables describing the climate, topography, substrate and cover of perennial vegetation. The phylogenetic alpha diversity was described using the mean pairwise distance (MPD) and the mean nearest taxon distance (NTD) metrics. The analyses showed that the lacertid species could be clustered into three main ecological groups: mesic (Podarcis vaucheri, Psammodromus algirus, Psammodromus blanci, Timon pater), xeric (Acanthodactylus blanci, Acanthodactylus boskianus, Acanthodactylus maculatus, Mesalina olivieri, Ophisops occidentalis), and hyperxeric (Acanthodactylus dumerilii, Acanthodactylus longipes, Acanthodactylus scutellatus, Mesalina guttulata). The analyses also indicated that environment had a weak influence on species richness (15.7% of explained variance), but a strong effect on the phylogenetic (76.5% NTD, 89.5% MPD) structure. The lacertid communities tended to be phylogenetically clustered on sandy substrates under arid climate conditions, and overdispersed under more humid climatic conditions.

Head stabilisation in fast running lizards

The cyclic patterns of terrestrial animal locomotion are frequently perturbed in natural environments. The terrain can be complex or inclined, the substrate can move unexpectedly and animals can misjudge situations. Loosing stability due to perturbations increases the probability of capture by predators and decreases the chance of successful prey capture and winning intraspecific battles. When controlled corrective actions are necessary to negotiate perturbations, animals rely on their exteroceptive and proprioceptive senses to monitor the environment and their own body movements. The vestibular system in the inner ear perceives linear and angular accelerations. This information enables gaze stabilisation and the creation of a stable, world-bound reference frame for the integration of the information of other senses. During locomotion, both functions are known to be facilitated by head stabilisation in several animals with an erect posture. Animals with a sprawled body posture, however, undergo very large body undulations while running. Using high speed video recordings, we tested whether they nevertheless stabilise their head during running, and how this is influenced by perturbations. We found that running Acanthodactylus boskianus lizards strongly stabilise their head yaw rotations when running on a flat, straight runway: the head rotation amplitude is only 4.76±0.99°, while the adjacent trunk part rotates over 27.0±3.8°. Lateral head translations are not stabilised (average amplitude of 7.4±2.0mm). When the lizards are experimentally perturbed by a large and unexpected lateral substrate movement, lateral translations of both the head and the body decrease (on average by 1.52±0.81mm). At the same time, the rotations of the head and trunk also decrease (on average by 1.62°±7.21°). These results show that head stabilisation intensifies because of the perturbation, which emphasises the importance of vestibular perception and balance in these fast and manoeuvrable animals.