Comparative demography of sympatric populations of Lacerta vivipara and Lacerta agilis

Summary A mark-recapture study was carried out in sympatric populations of Lacerta agilis and Lacerta vivipara in the Netherlands from 1976 to 1982. In most years the age structure of both populations was pyramidal. For both species life expectation of females was higher and on average they did live longer. Hence the sex ratio for adults deviated significantly from 1.0 in favour of females. Maximum age for Lacerta vivipara was 8 years (female) and for Lacerta agilis 12 years (male). The density of both species fluctuated around 100/ha. The biomass of Lacerta agilis was twice that of Lacerta vivipara. In Lacerta vivipara the 3rd and 4th calendar year class supplied 78% of total net reproduction; in Lacerta agilis the 4th, 5th, and 6th calendar year classes supplied 68%. In both populations the population replacement rate was 2. Population turnover time was 4.83 years for Lacerta agilis and 2.81 for Lacerta vivipara. The life history strategy of the Lacerta vivipara population is compared with six other European Lacertavivipara populations.     

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.     

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.

     

胎生蜥蜴的捕食行为及其食性分析

通过直接观察和胃容物分析对胎生蜥蜴（lacerta vivipara）的捕食行为和食性进行了研究。结果表明,胎生蜥蜴的捕食过程包括觅食、攻击前行为、攻击行为、猎物处死、吞食、食后清洁共6个主要步骤。在6～10月间,胎生蜥蜴的食谱中以昆虫和蜘蛛最多;不同月份的食物种类和数量不同;食物中以个体长为1～10mm食物数量频率最高;食物组成与生活环境中的无脊椎动物种类有极显著的相关。雌、雄体的食物生态位重叠度较高,而幼体和成体的食物生态位重叠度较低。     

胎生蜥泄殖系统的解剖

对胎生蜥Lacerta vivipara的排泄和生殖系统进行了解剖观察.胎生蜥的排泄系统由肾脏、输尿管和泄殖腔组成,左肾较右肾稍大,但在位置上没有明显差别;雄性生殖系统由精巢、输精管、附睾和半阴茎组成,左侧精巢位置较右侧稍接近身体前部且稍大;雌性生殖系统南卵巢和输卯管组成,左右卵巢在大小上无明显差别,但左侧卵巢比右侧卵巢略接近身体前部.对繁殖期和繁殖期后的生殖系统比较显示,生殖腺在繁殖期明显增大.胎生蜥的生殖系统与其他卵生和卵胎生类蜥蜴无明显差别.     

新疆产胎生蜥蜴染色体的研究

采用骨髓细胞制片法对分布在新疆阿勒泰地区的胎生蜥蜴Lacerta vivipara种群的染色体进行研究。结果表明,胎生蜥蜴的染色体全部为端着丝点,性别决定机制为Z1Z1Z2Z2/Z1Z2W型,雌雄染色体数目不同,雄性胎生蜥蜴二倍体染色体的数目为36,性染色体为Z1Z1Z2Z2型,染色体组型为2n=32+Z1Z1Z2Z2;雌性胎生蜥蜴二倍体染色体的数目为35,染色体组型为2n=32+Z1Z2W,性染色体为Z1Z2W型。从组型特征来看,新疆的胎生蜥蜴种群与欧洲中北部和俄罗斯地区的种群为同一大类群。     

Multiple origins of viviparity,or reversal from viviparity to oviparity? The European common lizard (Zootoca vivipara,Lacertidae) and the evolution of parity

The evolution of viviparity in squamates has been the focus of much scientific attention in previous years. In particular, the possibility of the transition from viviparity back to oviparity has been the subject of a vigorous debate. Some studies have suggested this reversal is more frequent than previously thought. However, none of them provide conclusive evidence. We investigated this problem by studying the phylogenetic relationships between oviparous and viviparous lineages of the reproductively bimodal lizard species Zootoca vivipara . Our results show that viviparous populations are not monophyletic, and that several evolutionary transitions in parity mode have occurred. The most parsimonious scenario involves a single origin of viviparity followed by a reversal back to oviparity. This is the first study with a strongly supported phylogenetic framework supporting a transition from viviparity to oviparity.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 1–11.     

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。     

Cytokines in the oviparity/viviparity transition: evidence of the interleukin-1 system in a species with reproductive bimodality, the lizard Lacerta vivipara

Placental viviparity is a reproductive strategy usually attributed to mammals. However, it is also present in other vertebrate species, e.g. in Squamate reptiles. Although the immunological mechanisms that allow the survival of the semi-allogenic embryo in maternal tissues are still largely unknown, cytokines seem to play an important role in mammalian reproduction. Previous studies in our laboratory showed that interleukin-1 (IL-1), a cytokine associated with implantation in mice, is also expressed at the materno-fetal interface of placental viviparous Squamates. In this study, we used the model of Lacerta vivipara, which exhibits reproductive bimodality, that is, the coexistence of oviparous and viviparous populations. By means of immunohistochemistry and anti-human antibodies, we showed that uterine tissues of L. vivipara (seven oviparous and six viviparous animals) expressed the two IL-1 isoforms, IL-1alpha and IL-1beta, and the type I IL-1 receptor (IL-1R tI) both at the pre-ovulatory stage and during gestation, with no significant difference between oviparous and viviparous females. In L. vivipara, as in most oviparous Squamates, an important phase of embryonic development takes place in the mother's oviduct, before egg-laying. Moreover, although thinner than in oviparous females, an eggshell membrane persists throughout gestation in viviparous females also, which develop a very simple type of placenta. The data suggest that immunological mechanisms that allow the survival of the semi-allogenic embryo in maternal tissues are independent of the timing or intimacy of contact between maternal and fetal tissues.     

Development of Regenerative Ability in the Lizard, Lacerta vivipara

Among animals which regenerate, it is usually observed thatyounger forms show greater powers than older ones. It becamepossible to investigate this correlation in lizards after thedevelopment of a culturing technique for the eggs of ovoviviparousreptiles (Panigel, 1956). Moffat and Bellairs (1964) amputatedthe tails of lizard embryos at various stages and examined themat hatching. Only the embryos amputated at near-hatching stagesshowed any regeneration. However, subsequent experiments onthe younger stages have shown that most of the embryos becomeconstricted and even amputated by the healing amniotic and allantoicmembranes. This younger group was therefore re-examined forregenerative ability under conditions where the formation ofconstrictions could be controlled. The results showed that smallasymmetrical outgrowths sometimes arise from a fraction of thestump area. These unusual regenerates were never seen to growlonger than one millimeter, or to differentiate cartilage ormuscle. The results suggest that normal regeneration is a processwhich cannot be elicited until a certain degree of maturityof the tail tissues has been attained, and that it is not necessarilybetter in young individuals or in tissues which are less welldifferentiated.     

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 contribution of phenotypic plasticity to adaptation in Lacerta vivipara

Correlation between intraspecific phenotypic variability and variation of environmental conditions could reflect adaptation. Different phenotypes may result from differential expression of a genotype in different environments (phenotypic plasticity) or from expression of different genotypes (genetic diversity). Populations of Lacerta vivipara exhibit larger adult body length, lower age at maturity, higher fecundity, and smaller neonatal size in humid habitats compared to dry habitats. We conducted reciprocal transplants of juvenile L. vivipara to test for the genetic or plastic origin of this variation. We captured gravid females from four populations that differed in the relative humidity of their habitats, and during the last 2 to 4 weeks of gestation, we manipulated heat and water availability under laboratory conditions. Juveniles were released into the different populations and families were divided to compare growth rate and survival of half-sibs in two environments. Growth rate and survival were assessed using capture-recapture techniques. Growth rate was plastic in response to postnatal conditions and did not differ between populations of origin. Survival differed between populations of origin, partially because of differences in neonatal body length. The response of juvenile body length and body condition to selection in the different habitats was affected by the population of origin. This result cannot be simply interpreted in terms of adaptation; however, phenotypic plasticity of fecundity or juvenile size most probably resulted in adaptive reproductive strategies. Adaptation to the habitat by means of genetic specialization was not detected. Further investigation is needed to discriminate between genetic and long-term maternal effects.     

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.     

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.     

小兴安岭北部胎生蜥蜴春季的栖息生境

分别于2005年5-7月和2006年5月在黑龙江省孙吴县境内方圆15 km的范围内采用样线法对胎生蜥蜴(Lacerta vivipara)春季的栖息生境进行了初步研究.通过对胎生蜥蜴栖息生境中的15个生境因子进行的频次百分比分析可以看出,在小兴安岭北部胎生蜥蜴春季的最适栖息生境是处于山体半阴半阳坡的中、下坡位,且坡度平缓的蒙古栎(Quercus mongolica).黑桦(Betula davurica)林中,林间落叶层较厚,具有适中的湿度和光照强度,且土质疏松,人为和天敌的干扰小.结果表明,胎生蜥蜴在春季一般选择具有良好的食物与隐蔽条件,以及能够提供充足热量的栖息生境,这是该物种对高纬度低温环境的一种适应.     

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.     

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.