Amphibians: suitable candidates for breeding-release programmes

Zoological parks are playing an increasingly important role in the management of threatened species through education, the maintenance of captive gene banks and the reintroduction of captive-bred animals into the wild. This paper discusses the suitability of amphibian species for reintroduction. The important features of amphibians for these programmes are highlighted, i.e., their high fecundity to allow rapid build-up of captive populations coupled with few behavioural problems with captive-bred animals, as well as the low cost of maintenance. The potential problems of inbreeding, poor retention of innate behavioural repertoires after multiple generation captive breeding, and the introduction of alien pathogens into wild populations are considered. Release programmes for two species, the Mallorcan midwife toad Alytes muletensis and the Puerto Rican crested toad Peltophryne lemur, are reviewed.     

Parasites of British Amphibians

Algal bioassays employing the test alga Selenastrum capricornutum Printz. are a relatively simple and reliable method of studying the effects of aquatic pollutants on plant growth in natural and waste waters. Details of algal bioassays based upon Liebig's ‘Law of the Minimum’ are described to enable students in schools and universities to assess the relative potential fertility of freshwater bodies, to evaluate the growth-promoting effects of nitrates and phosphates, to identify growth-limiting nutrients, and to determine the growth-inhibiting effects of toxic pollutants. Examples taken from students' investigations of Welsh river waters are cited in support.     

两栖动物的繁殖类型

根据多年对树蛙繁殖生态观察及参阅国内外有关两栖动物繁殖习性报告。综合报道两栖动物的繁殖类型。有助于理解两栖动物繁殖多样性及无羊膜动物向羊膜动物的演化。     

Immunological Tolerance in Amphibians

SYNOPSIS. A state of immunological tolerance, or specific unresponsivenessto foreign antigen, can be induced in amphibians by joiningtwo nonsibling embryos in parabiotic union. The induced toleranceis immunologically specific; the co-partners are tolerant ofeach other' santigens but do respond to unrelated antigens fromthird parties. The parabionts are blood-cell chimeras; eachcontains blood elements of the type proper to the other. Thedegree of chimerism wanes in the later life of the parabionts,which may be the consequence of the appearance of a new cloneof uninhibited reactive cells derived from the bone marrow. Tolerance to a particular antigen is interpreted as arisingby the deletion of the population of competent lymphocytes capableof responding to that antigen. The breakdown of tolerance occursthrough the emergence of a new population of antigen-reactivecells. In essence, a tolerant cell as a discrete entity doesnot exist.     

Effects of Ultraviolet Radiation on Amphibians: Field Experiments

SYNOPSIS. Numerous reports suggest that populations of amphibiansfrom a wide variety of locations are experiencing populationdeclines and/or range reductions. In some cases, unusually highegg mortality has been reported. Field experiments have beenused with increasing frequency to investigate ultraviolet radiationas one of the potential factors contributing to these declines.Results from field experiments illustrate that hatching successof eggs is hampered by ultraviolet radiation in a number ofspecies, while other species appear to be unaffected. Continuedmortality in early life-history stages may ultimately contributeto a population decline. Although UV-B radiation may not contributeto the population declines of all species, it may play a rolein the population decline of some species, especially thosethat lay eggs in open shallow water subjected to solar radiationand in those that have a poor ability to repair UV-induced DNAdamage.     

陕西周至老县城自然保护区两栖动物多样性调查

于2003年7月～8月和2004年5月对陕西周至老县城自然保护区进行两次实地考察,结合有关文献资料的报道结果,该地区有两栖动物8种,归隶2目、5科、8属,其中1种为未定种Scutiger sp.,与宁陕齿突蟾Scutiger ningshanensis相似,其代表的属和科在邻近的5个自然保护区目前均无发现与报道;与邻近的5个自然保护区的物种分布相似性比较表明,老县城自然保护区在两栖动物分布上与周至自然保护区更相近.     

Face lift

LEARNING OBJECTIVES: After reading this article, the participant should be able to: 1. Identify and describe the anatomy of and changes to the aging face, including changes in bone mass and structure and changes to the skin, tissue, and muscles. 2. Assess each individual's unique anatomy before embarking on face-lift surgery and incorporate various surgical techniques, including fat grafting and other corrective procedures in addition to shifting existing fat to a higher position on the face, into discussions with patients. 3. Identify risk factors and potential complications in prospective patients. 4. Describe the benefits and risks of various techniques. SUMMARY: The ability to surgically rejuvenate the aging face has progressed in parallel with plastic surgeons' understanding of facial anatomy. In turn, a more clear explanation now exists for the visible changes seen in the aging face. This article and its associated video content review the current understanding of facial anatomy as it relates to facial aging. The standard face-lift techniques are explained and their various features, both good and bad, are reviewed. The objective is for surgeons to make a better aesthetic diagnosis before embarking on face-lift surgery, and to have the ability to use the appropriate technique depending on the clinical situation.     

Circadian Rhythms in Amphibians and Reptiles: Ecological Implications

Circadian rhythms of amphibians and reptiles in the field and under semi-natural conditions and the underlying mechanisms, including the ways of entrainment to environmental cues and the oscillators driving the rhythms, have been reviewed. Studies on the behavioral rhythms in the field are meager in both amphibians and reptiles. In anuran amphibians, Xenopus adults showed more robust nocturnal locomotor activity than did tadpoles. This indicates the ecological significance of the differences in activity pattern shown by amphibians at different life stages, because differences between adults and young in the same environment may serve to isolate partially the young from the adults' cannibalism. In reptiles, free-running rhythms are more robust and continue for a longer time compared to amphibians. In both amphibians and reptiles, multi-photoreceptors are involved in photo-entrainment of circadian rhythms. The eyes, pineal complex and deep brain comprise a multi-oscillator system as well as a multi-photoreceptor system.     

Integrative Studies of Amphibians: From Molecules to Mating

SYNOPSIS. Studies of reproductive behavior in amphibians havebeen especially successful in synthesizing data produced frommolecular and physiological research with evolutionary parameters,such as measures of reproductive success. In particular, tworelatively new areas of amphibian research are highly amenableto synthetic studies. One area is the nature of chemical communicationby pheromone delivery in terrestrial salamanders. Male courtshippheromones, for example, are delivered to the female duringmating. These pheromones typically are received by the accessoryolfactory system and act (presumably via the hypothalamus) toincrease female receptivity. At an evolutionary level, pheromonedelivery can increase male courtship success and thus the likelihoodthat a given male will sire offspring. Variation in pheromonecomposition and effectiveness will permit us to trace the evolutionof the male pheromone on a phylogeny of related populationsand species. At a proximal level, salamander courtship pheromonesare being chemically analyzed in order to identify specificprotein components that affect female receptivity. It also willbe possible to determine whether chemical variation among malesis related to behavioral effectiveness. Thus, courtship pheromonedelivery is a behavior that has invited scrutiny from a combinationof evolutionary and mechanistic perspectives. The second researcharea that is gaining from a synthetic approach is the investigationof relationships between hormonal mechanisms and reproductivebehavior in field populations of anurans and salamanders. Amphibiansare an understudied group, and the area of hormone-behaviorrelationships is inspired by testable hypotheses based on studiesof other terrestrial vertebrates. The ability to correlate physiologicalmeasures with estimates of reproductive success identifies areasof amphibian research that will profit from continued attention.     

一种两栖动物年龄鉴定方法

采用金顶齿突蟾(10%福尔马林固定)为材料,对两栖类年龄鉴定方法进行了摸索.取其第2趾骨,通过长时间(24～36小时)流水冲洗、硬化、脱钙、脱水、透明、浸蜡、包埋、切片、贴片、脱蜡、复水、染色、脱水、透明、封片、镜检,观察其年轮,结果清晰.趾骨由内到外是骨髓腔、骨内膜﹑骨内板、骨外板和骨外膜,年轮在骨外板内.     

Paradise lost: Mitochondrial eve refuted

Being based solely on neontological data, all «unique parent» evolutionary hypotheses, of which «Mitochondrial Eve» is one, fall into the category ofscala naturae. Mathematical treatment of neontological data bases, using cladistic approaches does not confer the status of scientific hypotheses onto such scenarios. Apart from these fundamental problems, such hypotheses are flawed on a number of other bases, including the fact that there is a proportion of parental contribution to mitochondrial lineages, despite widely publicised statements that mithocondrial DNA in mammals is «strictly» maternally inherited. Other weaknesses of «unique mother» hypotheses on that their proponents endeavour to describe the evolution of diploid organisms on the basis of variability in extant haploid organelles, the evolution of which is delinked from that of the diploid organism. A further difficulty is that it is not possible to reconstruct interspecific relationships on the basis of intraspecific variability. There is a general ignorance among proponents of «unique mother» hypotheses regarding the distribution of biological variability on the surface of the globe, a fact which renders the molecular clock inaccurate, and which upsets the simplistic proposal that molecular diversity equates with time. «Unique mother» scenarios are also invalidated by the presence of shared chromosome and other polymorphisms in african great apes and humans at similar percentages in the different lineages, a fact which indicates that these evolving populations did not experience «bottlenecks». These and other difficulties effectively refute the «Mitochondrial Eve» hypothesis, which in any case much resembles creationism of a special kind, in which the offspring of a breeding pair are visualised as belonging to a species different from its parents. Such extreme examples of the punctuational mode of evolution are highly likely to be incorrect.