Age-structure and longevity of Common lizard (Lacerta vivipara) populations

Survivorship of L. vivipara in the field was estimated from visual census of the age-composition of two populations. There was approximately 90% mortality in the first year of life; but the mean expectation of life of an individual which survived to its first birthday was then between four and five years.     

Embryonic behaviour in the lizard, Lacerta vivipara

The behaviour of embryos of the lizard Lacerta vivipara has been studied in cultured eggs, removed from the mother. Spontaneous movements begin at a time when the embryo is still unresponsive to touch, and about two days before the appearance of reflex responses. The earliest movements consist of lateral flexion which gradually gives place to dorsiventral flexion. Embryonic movements are not necessarily related to contractions of the amnion. The activity of the embryo, as measured by the number of times movements were initiated and the amount of time spent in activity during a half hour period, rises to a plateau and then decreases sharply as the time of hatching approaches. Activity of the tail is prominent, particularly at times when other movements occur in rapid succession. Serpentine movements were not observed in embryos younger than stage 39; some prematurely born animals showed such activity in response to contact with the substratum. During embryonic life any part of the animal may move individually or in combination with any other part, such combined movements being unco-ordinated. In these respects the spontaneous motility of the lizard embryo closely resembles that of the chick. Statistical analysis of the embryonic movements provides evidence of rhythmic activity within the developing central nervous system.     

Host density and ectoparasite avoidance in the common lizard (Lacerta vivipara)

Increased transmission of parasites and diseases is generally considered as a major cost of social life. In this study we tested the hypothesis regarding ectoparasites as a cost of living in crowded habitats in the common lizard (Lacerta vivipara). We used two approaches to explore this question. First, we tested if ectoparasite load and prevalence are positively correlated with host density in the field. Second, we experimentally tested if lizards avoid parasitized conspecifics. Contrary to expectation, we found that (1) ectoparasite load is negatively correlated with lizard density; (2) prevalence does not significantly increase with density; (3) unparasitized lizards do not avoid parasitized conspecifics but are attracted by them whatever their parasite load. These findings suggest that ectoparasites cannot be considered as a cost of living at high density in the common lizard, in spite of the potential negative impact mites may have on lizard fitness. Received: 18 August 1996 / Accepted: 7 February 1997     

Environmental maternal effects on locomotor performance in the common lizard (Lacerta vivipara)

Environmental (i.e. non-genetic) maternal effects have the potential to associate the environmental conditions faced by mothers during gestation or before egg laying with the phenotype of their offspring. For this reason, maternal effects may play a major role in determining offspring phenotype independently of the genotype of the individuals, and can thus be considered a mechanistic basis of phenotypic plasticity. Despite the ecological and evolutionary implications of environmental maternal effects, few studies have experimentally investigated this phenomenon in reptiles. Here we report the results of an experimental laboratory study on the effects of maternal feeding rate and density on offspring locomotor performance in the common lizard (Lacerta vivipara). Lacerta vivipara is a viviparous lizard, and viviparity enhances the probability of a maternal influence on offspring phenotype. We focused on a particular phenotypic trait, maximal sprint running speed, because this trait is thought to be selectively important in squamates. Sprint speed was a repeatable trait, and it varied significantly among families. Maternal feeding rate significantly affected sprint speed, whereas density had no effect on this trait. The effect of maternal feeding rate differed according to the sex of the offspring and their body size, resulting in significant two-way and three-way interactions among these factors. In other words, the maternal feeding rate changed the shape of the allometric relationship between speed and size, but differently for males and females. The complexity of such effects makes it extremely difficult to offer an adaptive interpretation, but emphasizes the role played by the environment in shaping phenotypes among generations.     

The respiratory metabolism of a lizard (Lacerta vivipara) in supercooled and frozen states

We investigated the respiratory metabolism of the overwintering lizard Lacerta vivipara while in either supercooled or frozen states. With a variable pressure and volume microrespirometer and a chromatograph, we show that the oxygen consumption of the supercooled animals showed a nonlinear relationship with temperature and an aerobic metabolism demand between 0.5 and -1.5 degrees C. A significant increase in the respiratory quotient (RQ) values indicated an increasing contribution by the anaerobic pathways with decreasing temperature. In the frozen state, two phases are easily detectable and are probably linked to the ice formation within the body. During the first 5-6 h, the animals showed an oxygen consumption of 3.52 +/- 0.28 microl. g(-1). h(-1) and a RQ value of 0.52 +/- 0.09. In contrast, after ice equilibrium, oxygen consumption decreased sharply (0.55 +/- 0.09 microl. g(-1). h(-1)) and the RQ values increased (2.49 +/- 0.65). The present study confirms the fact that supercooled invertebrates and vertebrates respond differently to subzero temperatures, in terms of aerobic metabolism, and it shows that aerobic metabolism persists under freezing conditions.     

Prenatal exposure to testosterone increases ectoparasite susceptibility in the common lizard (Lacerta vivipara)

High levels of testosterone can benefit individual fitness, for example by increasing growth rate or ornament size, which may result in increased reproductive success. However, testosterone induces costs, such as a suppressed immune system, thereby generating trade-offs between growth or mate acquisition, and immunity. In birds and reptiles, females allocate steroids to their eggs, which may be a mechanism whereby females can influence the phenotype of their offspring. To our knowledge, only the benefits of early androgen exposure have been experimentally investigated to date. However, to understand this phenomenon, the costs also need to be evaluated. We manipulated testosterone levels in eggs of the viviparous common lizard and monitored growth, endurance and post-parturient responses to ectoparasites of the offspring. Testosterone-treated individuals had significantly higher growth rates than controls, but suffered a significant decrease in growth rate when exposed to ticks, whereas the corresponding difference for controls was non-significant. There was no difference in observed parasite load or leucocyte count between manipulated and control offspring. Thus, our results suggest that high testosterone levels during embryonic development have detrimental effects on immune function resulting in reduced growth rate, and that this must be taken into consideration when evaluating the potential adaptive value of maternal androgen allocation to eggs.     

Extraembryonic membrane development in a reproductively bimodal lizard, Lacerta (Zootoca) vivipara

Reproductive mode has been remarkably labile among squamate reptiles and the evolutionary transition from oviparity to viviparity commonly has been accompanied by a shift in the pattern of embryonic nutrition. Structural specializations for placental transfer of nutrients during intrauterine gestation are highly diverse and many features of the extraembryonic membranes of viviparous species differ markedly from those of oviparous species. However, because of a high degree of evolutionary divergence between the species used for comparisons it is likely that the observed differences arose secondarily to the evolution of viviparity. We studied development of the extraembryonic membranes and placentation in the reproductively bimodal lizard Lacerta vivipara because the influence of reproductive mode on the structural/functional relationship between mothers and embryos can best be understood by studying the most recent evolutionary events. Lecithotrophic viviparity has evolved recently within this species and, although populations with different reproductive modes are allopatric, oviparous and viviparous forms interbreed in the laboratory and share many life history characteristics. In contrast to prior comparisons between oviparous and viviparous species, we found no differences in ontogeny or structure of the extraembryonic membranes between populations with different reproductive modes within L. vivipara. However, we did confirm conclusions from previous studies that the tertiary envelope of the egg, the eggshell, is much reduced in the viviparous population. These conclusions support a widely accepted model for the evolution of squamate placentation. We also found support for work published nearly 80 years ago that the pattern of development of the yolk sac of L. vivipara is unusual and that a function of a unique structure of squamate development, the yolk cleft, is hematopoiesis. The structure of the yolk sac splanchnopleure of L. vivipara is inconsistent with a commonly accepted model for amniote yolk sac function and we suggest that a long standing hypothesis that cells from the yolk cleft participate in yolk digestion requires further study.     

Density, social information, and space use in the common lizard (Lacerta vivipara)

Socially acquired information is widespread in the animal kingdom.Many individuals make behavioral decisions based on such socialinformation. In particular, individuals may decide to leaveor select their habitat based on social information. Few studieshave investigated the role of density-related information, apotential social cue about habitat quality in dispersal. Here,we tested for the possibility that the phenotype of intrudercommon lizards (Lacerta vivipara) may inadvertently carry informationabout their natal population density. We found that such informationuse is likely. The behavior of focal lizard was influenced bythe natal population density of the intruder it was interactingwith. This suggests that individuals may use the behavior ofothers to acquire appropriate information about surroundingsand to base spatial decisions on this information. Density-relatedinformation may then affect individual movement decisions andthus metapopulation dynamics.     

Storage lipids in the lizard Lacerta vivipara: a quantitative study

Lipids in various tissues of Lacerta vivipara were measured at three times of the year: immediately after hibernation, mid-season, and immediately prior to hibernation. Lipid deposits in the abdominal fat bodies and the caudal fat bands fluctuated seasonally, but at any time showed a marked positive allometry with body length and weight; the functional significance of this relationship is not known. Carcass lipid and liver weight were isometric with body length and weight.     

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.     

胎生蜥蜴断尾及再生的研究

对胎生蜥蜴的断尾及再生进行了统计和观察,结果表明：胎生蜥蜴幼体断尾率为28．26％,成体断尾率为45．45％。说明承受着很大的生存压力;断尾活动时间与断尾的长度及断尾部位有关;再生尾中有一节鳞片明显较其它鳞片长;再生尾明显较原尾生长速度快。     

Energie-Bilanz eines Poikilothermen(Lacerta vivipara)

Zusammenfassung 1. Die Energiebilanz eines Tieres ist quantitativ im wesentlichen durch seinen Wärmehaushalt bestimmt oder mindestens in Wärmeäquivalenten ausdrückbar.2. Der Energiewechsel beruht auf zwei Hauptgruppen von Prozessen: Stoffwechselprozessen im Körperinneren und Wärmeaustausch zwischen Tierkörper und Umwelt.3. In beiden Gruppen treten regulative und nicht regulative Vorgänge auf. Die Regulation beim Wärmeaustausch zwischen Tierkörper und Umwelt beruht auf entsprechenden Verhaltensweisen.4. Der Unterschied zwischen Homoiothermen und Poikilothermen liegt nicht darin, daß die Regulationsmöglichkeit der Körpertemperatur nur den ersteren vorbehalten wäre (beide zeigen eine gewisse — und nur eine gewisse — Regulationsmöglichkeit), sondern darin, daß die Energiebilanz der Poikilothermen zum wesentlichen Teil durch den Wärmeaustausch mit der Umwelt beherrscht wird und daher auch die Regulation der Körpertemperatur wirksam nur durch Verhaltensweisen — die den Wärmeaustausch in die gewünschte Richtung lenken — erreicht werden kann.5. Aus der Beherrschung der Energiebilanz durch den Wärmeaustausch mit der Umwelt folgt auch, daß die Regulationskapazität der Poikilothermen weit geringer ist als die der Homoiothermen — obwohl natürlich auch deren Regulationskapazität begrenzt ist.6. Ein weiterer charakteristischer Unterschied zwischen Homoiothermen und Poikilothermen liegt darin, daß bei den ersteren die Überforderung der Temperaturregulation meist katastrophal endet, bei den letzteren hingegen eine normale Reaktion auslöst, nämlich den Übergang zu einer mehr oder weniger inaktiven, mindestens nicht vollaktiven Lebensweise. Aus verschiedenen Anzeichen läßt sich sogar schließen, daß Poikilotherme ein ständiges Leben im Aktivitätstemperaturbereich nicht ertragen könnten.7. FürLacerta vivipara wird eine möglichst komplette Energiebilanz gegeben.

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Energy balance of a poikilothermic animal(lacerta vivipara)

The main differences between homoiothermic and poikilothermic animals are considered on the basis of information from literature and results obtained by the author. It is not the occurrence of thermoregulation per se which constitutes the main differences between representatives of these two groups, but rather the manner in which this thermoregulation is performed. Whereas homoiothermic animals regulate by means of metabolic processes and changes in behaviour, poikilothermic animals employ the latter mechanism almost exclusively. InLacerta vivipara the close relationship between thermal balance and environmental factors is demonstrated on the basis of experimental results and calculations.

     

Variation of reproductive traits in a population of the lizard Lacerta vivipara

Variation in reproductive traits (sexual maturity, clutch size, clutch weight, mean egg mass, newborn weight) was studied during a four year period in a population of the live-bearing lizard Lacerta vivipara . Sexual maturity was associated with attaining a minimum body size. Clutch size increased with female body length and litter weight increased with clutch size. A major component of the within year variation in these reproductive traits was attributable to female size. Analysis of successive clutches in individual females indicated that a significant fraction of the variation in litter size, adjusted for female length, was due to consistent differences between individuals. Newborn weight varied within and among litters, but no relations between hatchling mass or mean egg mass in a litter and other traits were detected.
Size-adjusted reproductive performances remained constant during the course of this study, even though environmental conditions (weather factors, food availability) varied annually. Observed among year variations in reproductive characteristics were attributable to differences in the body size distributions of the adult females.     

Effects of maternal parasite load on offspring life-history traits in the common lizard (Lacerta vivipara)

We studied the effect of maternal ectoparasite load (measured at parturition) on the life-history traits of the offspring of the host Lacerta vivipara, the European common lizard. The ectoparasite, a mite belonging to the family Laelapidae, had a detrimental effect on its host: parasite load was associated with increased host mortality, and was negatively correlated with host body mass. Parasite load was persistent over time, suggesting that parasite load can be predictable. Offspring of highly parasitised mothers had higher values of several fitness components early in life than offspring of parasite-free mothers or lightly infested mothers. This was expressed in terms of increased F₁ yearling growth rate, and reproductive investment at first reproduction (measured as F₂ hatchling mass). These results are interpreted as a host adaptation to attenuate the impact of parasites. Indeed, if high parasite loads arise from long exposure time to a constant population of parasites, and if the negative effects of parasites are additive over time, hosts could reduce the impact of parasites simply by investing more during the earlier stages of life. Naturally, having better performance early in life should lead to higher mortality rates and/or lower fecundity later in life.     

Stress and body condition as prenatal and postnatal determinants of dispersal in the common lizard (Lacerta vivipara)

Dispersal is a complex phenomenon affected by multiple factors. Among the factors that influence dispersal in the common lizard (Lacerta vivipara), poor maternal body condition and stress are known to decrease dispersal propensity of juveniles. But the effect of individual factors on dispersal could change when several of them act concurrently or at different developmental stages. Prenatal factors can affect clutch and/or juvenile characteristics that later affect dispersal. Postnatal influences are mainly exerted on juvenile dispersal behavior. We investigated the role of body condition and stress on dispersal at a prenatal and a postnatal stage. Stress was mimicked by experimentally increasing corticosterone levels in pregnant females and recently born juveniles. We considered (1). the influence of maternal body condition and prenatal corticosterone treatment on clutch, juvenile characteristics and on dispersal behavior and (2). the influence of juvenile body condition and postnatal corticosterone treatment on juvenile dispersal behavior. There was an interaction between maternal condition and prenatal corticosterone treatment on juvenile dispersal. Dispersal decreased with maternal corticosterone increase only in juveniles from the more corpulent females, while it increased with juvenile body condition. Good maternal body condition affected clutch and juvenile characteristics favoring dispersal, while elevation of corticosterone level (stress) exerted the opposite effect. Juvenile body condition favored dispersal, while there was no effect of postnatal corticosterone treatment on juvenile dispersal propensity.     

Mating order-dependent female mate choice in the polygynandrous common lizard Lacerta vivipara

Recent studies indicate that directional female mate choice and order-dependent female mate choice importantly contribute to non-random mating patterns. In species where females prefer larger sized males, disentangling different hypotheses leading to non-random mating patterns is especially difficult, given that male size usually correlates with behaviours that may lead to non-random mating (e.g. size-dependent emergence from hibernation, male fighting ability). Here we investigate female mate choice and order-dependent female mate choice in the polygynandrous common lizard (Lacerta vivipara). By sequentially presenting males in random order to females, we exclude non-random mating patterns potentially arising due to intra-sexual selection (e.g. male–male competition), trait-dependent encounter probabilities, trait-dependent conspicuousness, or trait-dependent emergence from hibernation. To test for order-dependent female mate choice we investigate whether the previous mating history affects female choice. We show that body size and body condition of the male with which a female mated for the first time were bigger and better, respectively, than the average body size and body condition of the rejected males. There was a negative correlation between body sizes of first and second copulating males. This indicates that female mate choice is dependent on the previous mating history and it shows that the female’s choice criteria are non-static, i.e. non-directional. Our study therefore suggests that context-dependent female mate choice may not only arise due to genotype-environment interactions, but also due to other female mating strategies, i.e. order-dependent mate choice. Thus context-dependent female mate choice might be more frequent than previously thought.     

Colour variation and alternative reproductive strategies in females of the common lizard Lacerta vivipara

Within-sex colour variation is a widespread phenomenon in animals that often plays a role in social selection. In males, colour variation is typically associated with the existence of alternative reproductive strategies. Despite ecological conditions theoretically favourable to the emergence of such alternative strategies in females, the social significance of colour variation in females has less commonly been addressed, relative to the attention given to male strategies. In a population of the common lizard, females display three classes of ventral colouration: pale yellow, orange and mixed. These ventral colours are stable through individual's life and maternally heritable. Females of different ventral colourations displayed different responses of clutch size, clutch hatching success and clutch sex-ratio to several individual and environmental parameters. Such reaction patterns might reflect alternative reproductive strategies in females. Spatial heterogeneity and presence of density- and frequency-dependent feedbacks in the environment could allow for the emergence of such alternative strategies in this population and the maintenance of colour variation in females.