Reptilian myotomal myogenesis-lessons from the sand lizard Lacerta agilis L. (Reptilia, Lacertidae)Update

Reptilian myotomal myogenesis is poorly understood. This paper reports on structural, ultrastructural and immunocytochemical studies of muscle differentiation in sand lizard (Lacerta agilis) embryos. During somitogenesis, the somites are composed of epithelial vesicles with a centrally located somitocoel. At later developmental stages the ventral portion of the somite cortex disaggregates into the sclerotome mesenchyme, while the dorsal wall of the somite differentiates into dermomyotome. At these developmental stages, mononucleated cells of the dermomyotome are Pax3-positive. The dermomyotome layer forms the dorsomedial and ventromedial lips. The myotome is first composed of mono- and then of multinucleated myotubes and small mononucleated cells that occur in the vicinity of the myotubes. These mononucleated cells exhibit low proliferative potential as revealed by the use of PCNA antibody. At subsequent stages of myogenesis the mononucleated cells express Pax7 protein, a marker of satellite cells, and assume ultrastructural features characteristic of satellite cells. Some of the mononucleated cells contribute to muscle growth, being involved in fusion with differentiating muscle fibers. This study revealed similarities of myotomal myogenesis in reptiles to that of other vertebrates.     

Offspring-driven local dispersal in female sand lizards (Lacerta agilis)

We report on a field study in which determinants of female breeding dispersal (i.e. the shift in the mean home range coordinates between successive breeding events) was investigated. Offspring were released in full sib groups (or half sib ones if there was within-clutch multiple paternity) at a separation distance from the females that varied between 'families'. This allowed for analysis of 'offspring nearness' effects on maternal dispersal. When a female's offspring were released more closely to her, she responded with greater dispersal. Furthermore, when the data set was truncated at 100 m maternal-offspring separation distance at offspring release (because perception at longer distances is likely to be unrealistic), maternal dispersal resulted in greater separation distance between female and offspring in the following year. A corresponding analysis for juveniles revealed no effect of maternal nearness on offspring dispersal but identified a significant effect of clutch size, to our surprise with dispersal declining with increasing clutch size. We discuss this result in a context of the 'public information hypothesis' (reinterpreted for juveniles in a nonsocial foraging species), suggesting that conspecific abundance perhaps acts as an indicator of local habitat quality. Thus, our analysis suggests a microgeographic structuring of the adult female population driven by genetic factors, either through inbreeding avoidance, or from simply avoiding individuals with a similar genotype regardless of their pedigree relatedness, while a nongenetic factor seems more important in their offspring.     

Proximate determinants of telomere length in sand lizards (Lacerta agilis)

Telomeres are repeat sequences of non-coding DNA that cap the ends of chromosomes and contribute to their stability and the genomic integrity of cells. In evolutionary ecology, the main research target regarding these genomic structures has been their role in ageing and as a potential index of age. However, research on humans shows that a number of traits contribute to among-individual differences in telomere length, in particular traits enhancing cell division and genetic erosion, such as levels of free radicals and stress. In lizards, tail loss owing to predation attempts results in a stress-induced shift to a more cryptic lifestyle. In sand lizard (Lacerta agilis) males, telomere length was compromised by tail regrowth in a body size-related manner, so that small males, which already exhibit more cryptic mating tactics, were less affected than larger males. Tail regrowth just fell short of having a significant relationship with telomere length in females, and so did age in males. In females, there was a significant positive relationship between age and telomere length. We conclude that the proximate effect of compromised antipredation and its associated stress seems to have a more pronounced effect in males than in females and that age-associated telomere dynamics differ between the sexes.     

Fluctuations in incubation temperature affect incubation duration but not morphology,locomotion and growth of hatchlings in the sand lizard Lacerta agilis (Lacertidae)

Li, H., Zhou, Z.‐S., Ding, G.‐H. and Ji, X. 2011. Fluctuations in incubation temperature affect incubation duration but not morphology, locomotion and growth of hatchlings in the sand lizard Lacerta agilis (Lacertidae). —Acta Zoologica (Stockholm) 00 : 1–8. Studies looking for potential effects of temperature and temperature fluctuations on phenotypic traits of reptile hatchlings have shown species variation, but have not always allowed a distinction between effects of fluctuation per se and temperature extremes themselves. To examine whether incubation temperature fluctuation has a key role in influencing the phenotype of offspring, we incubated eggs of the sand lizard Lacerta agilis at one of the four temperature regimes (27, 27 ± 2, 27 ± 4 and 27 ± 6 °C). We found that: (1) hatchlings incubated under the four temperature regimes did not differ from each other in any of the morphological and physiological traits examined; (2) interactions that included temperature treatment did not affect any trait examined; (3) the mean incubation length was longer in the 27 ± 6 °C treatment than in the other three treatments; and (4) female hatchlings were shorter in head length and width but longer in snout‐vent length as well as abdomen length than males derived from the same‐sized egg. Our data show that both the type and the magnitude of temperature variation can affect incubation length. We found no evidence for phenotypic divergence in responses to temperature fluctuations during incubation and therefore suggest that temperature variation does not affect the phenotype of hatchlings in L. agilis.     

Malformed offspring,sibling matings,and selection against inbreeding in the sand lizard (Lacerta agilis)

We demonstrated that sand lizards (Lacerta agilis) are more likely to have malformed offspring when they mate with siblings. Offspring with malformations, such as deformed limbs and heads, have zero survival in a natural population. Normal-looking siblings of malformed hatchlings also had a reduced survival in the wild, compared to offspring from clutches in which all siblings appeared normal. The proportion of malformed hatchlings in the natural population was ca. 10%, in spite of differences in juvenile dispersal between males and females. Male juveniles disperse significantly further from their natal sites than do female juveniles.     

UV-deprived coloration reduces success in mate acquisition in male sand lizards (Lacerta agilis)

Background

Recent work on animal signals has revealed a wide occurrence of UV signals in tetrapods, in particular birds, but also in lizards (and perhaps other Squamate reptiles). Our previous work on the Swedish sand lizard (Lacerta agilis) has verified, both in correlative selection analyses in the wild and with laboratory and field experiments, the importance of the green ‘badge’ on the body sides of adult males for securing mating opportunities, probably mostly through deterring rival males rather than attracting females. The role of UV in communication has, however, never been examined.

Methodology/Principal Findings

Here we show that when measured immediately after spring skin shedding, there is also signaling in the UV. By UV-depriving the signal (reflectance) with sun block chemicals fixated with permeable, harmless spray dressing, we show that males in the control group (spray dressing only) had significantly higher success in mate acquisition than UV-deprived males.

Conclusions/Significance

These results suggest that at least two colour traits in sand lizards, badge area and UV, contribute to rival deterrence and/or female choice on UV characters, which elevates success in mate acquisition in UV intact male sand lizards.     

Promiscuity in sand lizards (Lacerta agilis) and adder snakes (Vipera berus): causes and consequences

We review postcopulatory phenomena in the Swedish sand lizard (Lacerta agilis) and adder (Vipera berus), and in particular, links between female promiscuity, determinants of paternity, and offspring viability. In both species, females mate multiply and exhibit a positive relationship between the number of partners and offspring viability. We conclude that this relationship is most likely the result of variable genetic compatibility between mates arising from postcopulatory phenomena, predominantly assortative fertilization with respect to parental genotypes. However, males who were more successful at mate acquisition were also more successful in situations of sperm competition, suggesting a possible link between male (diploid and haploid) genetic quality per se and probability of fertilization. Neither the number of partners nor the number of matings influenced the risk of infertility in sand lizards, suggesting that selection for reduced risk of infertility is not a sufficient explanation for maintaining female promiscuity in this population. Finally, we conclude that the relatively low genetic variability exhibited by our study populations may have facilitated detection of genetic benefits compared to more outbred ones. However, recent work derived from outbred populations in other taxa suggest a greater generality of the principles we discuss than previously may have been appreciated.     

Locomotor performance of sand lizards (Lacerta agilis): effects of predatory pressure and parasite load

Locomotor performance affects foraging efficiency, predator avoidance and consequently fitness. Agility and speed determine the animal's social status and reflect its condition. In this study, we test how predatory pressure and parasite load influences locomotor performance of wild specimens of the sand lizard Lacerta agilis. Animals were chased on a 2-metre racetrack. Lizards with autotomy ran significantly faster than lizards with an intact tail, but there was no significant difference in running speed between individuals with fresh caudal autotomy and regenerated tails. Parasite presence and load, age and sex had no significant effect on speed. Our results indicate that autotomy either alters locomotory behaviour or that individuals with autotomised tails were those that previously survived contact with predators, and therefore represented a subgroup of the fastest individuals. Therefore, in general, predatory pressure but not parasites affected locomotor performance in lizards.     

Ultrastructure of the juxtaglomerular apparatus of the kidney and of the peripolar cells in the sand lizard (Lacerta agilis)

In 9 sand lizards ultrastructure of the juxtaglomerular complex of the kidney has been studied. It is presented as juxtaglomerular cells, situating in the middle tunic of the afferent glomerular arteriole near the vascular pole of the renal corpuscle. Cytoplasm of these cells contains secretory granules at various stages of development: young, maturing and mature, as well as solid corpuscles and myofilaments. In some nephrons primitive forms of the macula densa and the juxtaglomerular island occur. Their presence demonstrates phylogenetically new structural organization of the juxtaglomerular complex in lizards. For the first time in reptilia peripolar cells are found, they are situated on the basal membrane of the external part of the glomerular capsule near the vascular pole of the renal corpuscle. A suggestion is made on their functional interconnection with the juxtaglomerular complex.     

Kinematic analysis of drinking by the lacertid lizard, Lacerta viridis (Squamates, Scleroglossa)

The kinematics of drinking of Lacerta viridis were analysed. A drinking bout is composed of four phases: approach, immersion, emersion and withdrawal. The tongue and gravity are central to moving water through successive compartments of the buccal cavity and into the oesophagus. Upon the basis of formifunction analysis of water intake and transport, a kinematic model of drinking in lizards is proposed.     

Relationships of lacertid lizards (Reptilia: Lacertidae) estimated from mitochondrial DNA sequences and morphology.

DNA sequences from parts of the 12S, 16S and cytochrome b mitochondrial genes, which totalled 1049 aligned base pairs, were used to estimate the relationships of 49 species of Lacertidae, including representatives of 19 out of the 23 recognized genera and 23 species of the paraphyletic genus Lacerta. These data were used, together with morphological information, to estimate the relationships within the family. Molecular evidence corroborates the monophyletic status of many genera and species groups originally based on morphology. It indicates that Psammodromus forms a clade with Gallotia, which is the sister taxon of all other lacertids. These comprise three units: the primarily Afrotropical armatured group; the largely Oriental Takydromus; and the west Palaearctic Lacerta and its derivatives, Podarcis and Algyroides. Morphology also supports the first three assemblages, but suggests that they are derived from a paraphyletic Lacerta. Within Lacerta and its allies, DNA sequence analysis corroborates the affinity of some members of each of the subgenera Lacerta s. str. and Timon, and of the L. saxicola group. It also supports the relationship of L. monticola, L. bonnali and L. horvathi, and suggests that the L. parva--L. fraasi clade and L. brandli are not related to Psammodromus Gallotia, as morphology indicates, but instead are associated respectively with the L. danfordi and L. saxicola groups. DNA sequence data provide additional evidence that the eastern Arabian ''Lacerta'' jayakari and ''L.'' cyanura are members of the armatured clade and also sister species. Our analysis supports an origin for present lacertids in west Eurasia. The armatured clade invaded Africa, probably in the mid-Miocene, spreading widely and evolving increasingly xeric-adapted forms, one lineage of which later moved back into the Palaearctic. ''Lacerta'' jayakari and ''L.'' cyanura are assigned to Omanosaura, Lutz and Mayer 1986. The name Gallotiinae Cano, Baez, Lopez-Jurado & Ortega, 1984 is available for the Gallotia-Psammodromus clade, Eremiainae Shcherbak 1975 for the armatured clade and Lacertinae for Lacerta, Podarcis and Algyroides. Two new subgenera of Lacerta are proposed here: Caucasilacerta for L. saxicola and its allies, and Parvilacerta for L. parva and L. fraasi.     

Patterns of daily behaviour in two lizard species Lacerta agilis L. and Lacerta vivipara Jacquin

Summary During the period May to August 1978, individuals of both Lacerta agilis and Lacerta vivipara were observed in a specially constructed out-door vivarium. The daily patterns of behaviour of the two species were recorded along with surface and air temperatures. Daily activity of both species followed a similar basic pattern but was modified by variations in the local weather. Adults of L. vivipara reached a thermal preferendum more quickly and had a longer daily activity period than adults of L. agilis. The larger L. agilis can increase its period of activity by making use of different thermal conditions in a diverse habitat with varied vegetation structure under conditions of high solar radiation. The status of viable populations of L. agilis could be maintained or enhanced by management aimed at modifying the microenvironment of the lizard's habitat.     

The movement patterns of lacertid lizards: speed, gait and pauses in Lacerta vivipara

Lacerta vivipara moving across an open space at their normal activity temperature alternate bursts of locomotion with short pauses which tend to occur at the extremes of the limb cycle, i.e. when individual limbs are maximally adducted or retracted and the spinal cord is maximally flexed in the lateral plane. The movement bursts and pauses in adult lizards have mean durations of 0–30 and 012 s, respectively, and within bursts the lizards move at a mean speed of 14–6 cm s^-1. Movement in juvenile lizards is 2–5 times faster (relative to body length) and the pauses are of longer duration (mean = 019 s), giving the locomotion of juveniles a more jerky appearance. Lizards which are chasing crickets increase the speed and the duration of locomo-tory bursts, although the pauses persist. Lizards which are searching for a previously perceived cricket increase pause duration (mean = 0–40 s). Lizards which are fleeing from a sudden disturbance move at almost twice (juveniles) or 3–7 times (adults) the speed of foraging animals: the pauses persist, although at much reduced frequency. Increases in speed result from increases in both stride length (Λ) and stride frequency (n); the ratio Λ/ n appears to remain constant at 006. The significance of these observations is discussed, although the functions of the pauses cannot yet be explained.     

Nuclear and mtDNA-based phylogeny of southern African sand lizards, Pedioplanis (Sauria: Lacertidae)

The diversity of lacertid lizards in Africa is highest in the southern African subcontinent, where over two-thirds of the species are endemic. With eleven currently recognized species, Pedioplanis is the most diverse among the southern African genera. In this study we use 2200 nucleotide positions derived from two mitochondrial markers (ND2 and 16S rRNA) and one nuclear gene (RAG-1) to (i) assess the phylogeny of Pedioplanis and (ii) estimate divergence time among lineages using the relaxed molecular clock method. Individual analyses of each gene separately supported different nodes in the phylogeny and the combined analysis yielded more well supported relationships. We present the first, well-resolved gene tree for the genus Pedioplanis and this is largely congruent with a phylogeny derived from morphology. Contrary to previous suggestions Heliobolus/Nucras are sister to Pedioplanis. The genus Pedioplanis is monophyletic, with P. burchelli/P. laticeps forming a clade that is sister to all the remaining congeners. Two distinct geographic lineages can be identified within the widespread P. namaquensis; one occurs in Namibia, while the other occurs in South Africa. The P. undata species complex is monophyletic, but one of its constituent species, P. inornata, is paraphyletic. Relationships among the subspecies of P. lineoocellata are much more complex than previously documented. An isolated population previously assigned to P. l. pulchella is paraphyletic and sister to the three named subspecies. The phylogeny identifies two biogeographical clades that probably diverged during the mid-Miocene, after the development of the Benguella Current. This probably led to habitat changes associated with climate and, in conjunction with physical barriers (Great Escarpment), contributed towards speciation within the genus Pedioplanis.     

Interrelationships and evolution of the east Asian grass lizards, Takydromus (Squamata: Lacertidae)

The east Asian lacertid lizard genus, Takydromus , is well-defined but its relationships to other primitive Palaearctic lacertids are still uncertain and, although it has similarities to the lower Miocene Miolacerta, Takydromus does not appear to be identical with this. The 16 or 17 recognizable species are reviewed and a key provided for their identification; the remaining area of uncertainty about species boundaries is the Takydromus sexlineatus group in Assam. A phylogeny for Takydromus is estimated using a data set of 35 morphological characters drawn from external features, skeleton and soft-parts. There are two main constituent clades which may be informally recognized as Takydromus s.s. and Platyplacopus. Platyplacopus is subtropical and perhaps relict, whereas Takydromus ranges from temperate to tropical areas. The two clades have different ranges of eggs per clutch. In both of them, elongate forms that climb extensively in flimsy vegetation have evolved and have independently acquired similar features that confer performance advantages in this situation. Interestingly, the order of assembly of tliese features is markedly different.