桓仁林蛙蝌蚪胚后发育的初步观察

本文对桓仁林蛙蝌蚪胚后发育的过程和形态特征进行了观察、测量和描述,并与中国林蛙和昆嵛林蛙进行了比较.胚后发育可分为19期,对其后肢芽、趾、前肢的发育,唇齿的变化过程,口、鼻、眼的位置与形状,以及肛管与尾的变化等方面做了系统的描述.     

桓仁林蛙与东北林蛙蝌蚪的形态特征及比较

桓仁林蛙（Rana huanrenensis Liu,Zhang,＆ Liu,1993）为一种与东北林蛙（Rana dybowskii）同域分布的林蛙,但其分布区域较狭窄.通过对其蝌蚪的形态特征描述及测量相关的形态学量度并和东北林蛙比较,发现在体色、体型、尾部形态以及身体各部位量度比值等方面存在显著性差异.桓仁林蛙的蝌蚪外形与流水型的蝌蚪相类似,而东北林蛙的蝌蚪则属于典型的静水型蝌蚪.     

中国林蛙越冬死亡率的调查分析

中国林蛙（Rana chensinensis）越冬是林蛙人工养殖中的重要环节.在休眠期间林蛙死亡率高达31%,且以优良种蛙较多.利用自动控温水族箱模拟林蛙越冬,揭示这个阶段林蛙的生理机制,既具有理论意义,又可指导实践,减少种蛙的死亡.     

用三维图象量测卵裂前蛙卵膜分子的三维运动

两栖类卵第一次卵裂前,缩时电影显示出卵表面有收缩波。由于卵的体积未变,在收缩时卵的高度必然增加。Sawai(1978)利用棱镜侧面摄取了蝾螈卵轮廓的高度变化,证实了卵裂前卵最高处的高度确有增加。但这一方法不能测知整个卵表面各处的高度变化,而且仅是二维的。在林蛙卵上,我们用荧光漂白恢复技术发现第一次卵裂前卵表面分子有规律性的流动,推测这是卵球的张弛。为了进一步     

Behavioral responses of American toad and bullfrog tadpoles to the presence of cues from the invasive fish, Gambusia affinis

The introduction of non-native predators is thought to have important negative effects on native prey populations. The susceptibility of native prey to non-native or introduced predators may depend on their ability to respond appropriately to the presence of these non-native predators. We conducted a laboratory based behavioral experiment to examine the response of American toad (Bufo americanus) and bullfrog (Rana catesbeiana) tadpoles to the presence of cues from the introduced mosquitofish (Gambusia affinis), a potential tadpole predator. Neither the American toad tadpoles nor the bullfrog tadpoles responded behaviorally to the presence of mosquitofish cues. If tadpoles are unable to respond to the presence of mosquitofish cues appropriately, then their ability to avoid predation by mosquitofish may be compromised and this may contribute to the impacts of mosquitofish on some tadpole populations.     

Die Ontogenese der aminhaltigen Neuronensysteme im Gehirn von Rana temporaria

Zusammenfassung Vorkommen und Verteilung biogener Amine im Gehirn von Rana temporaria-Kaulquappen wurden fluoreszenzmikroskopisch untersucht. Catecholaminhaltige Perikaryen erscheinen ab Stadium 20 im Nucleus reticularis mesencephali, im Tuber cinereum und im Bulbus olfactorius, ab Stadium 22 in den Flügelplatten der Medulla oblongata und in der Area praeoptica. Ab Entwicklungsstufe 20 zeigen sich ventrolateral in Medulla oblongata und Mittelhirn, lateral vom Organon vasculosum hypothalami, im Bereich des medialen Vorderhirnbündels und im Striatum catecholaminhaltige Faseranschwellungen, ab Stadium 22 außerdem in der Eminentia mediana und dem Hypophysenzwischenlappen, in der Commissura transversa (bis zur Stufe 26), in der Commissura anterior (bis zur Stufe 26) und in der Pars ventrolateralis nuclei lateralis septi. Im Striatum ist von dieser Entwicklungsstufe an ein zweites Areal mit grün fluoreszierenden Varikositäten nachweisbar. Ab Stadium 26 finden sich auch in der Pars dorsolateralis des lateralen Septumkerns catecholaminhaltige Faseranschwellungen.Ab Entwicklungsstufe 22 sind 5-HT-haltige, gelb fluoreszierende Perikaryen im Nucleus raphes und in seiner Umgebung zu beobachten, gelb fluoreszierende Varikositäten im Nucleus interpeduncularis und zwischen medialem und lateralem Septumkern.

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Ontogeny of the amine-containing nerve cell systems in the brain of Rana temporaria

Summary The occurrence and distribution of biogenic amines in the brain of Rana temporaria tadpoles have been investigated with the fluorescence-microscope. From the embryonic developmental stage 20 onwards catecholamine-containing cell bodies are shown to be present in the nucleus reticularis mesencephali, the tuber cinereum and the olfactory bulb, and from stage 22 onwards also within the dorsolateral areas of the medulla oblongata and within the preoptic area. Catecholamine-containing enlargements of nerve fibres occur in the ventrolateral parts of the medulla oblongata and the midbrain, in an area lateral to the hypothalamic organon vasculosum, within the region of the medial forebrain bundle and within the striatum, in all stages following stage 20. These enlargements also occur in the median eminence and the pars intermedia of the hypophysis, in the commissura transversa (up to stage 26), in the commissura anterior (also up to stage 26) and in the pars ventrolateralis nuclei lateralis septi in all stages after 22. From the same stage onwards a second area of green fluorescent varicosities can be demonstrated within the striatum. After stage 26 catecholamine-containing enlargements of nerve fibres additionally are to be found in the dorsolateral part of the lateral septal nucleus.After appearing at stage 22 5-HT-containing, yellow fluorescent perikarya are to be observed within the nucleus raphes and its neighbourhood, and yellow fluorescent varicosities in the interpeduncular nucleus and in an area between the medial and the lateral septal nucleus.

Herrn Professor Dr. med. W. Bargmann zum 65. Geburtstag gewidmet.     

Cytoskeletons of retinal pigment epithelial cells: Interspecies differences of expression patterns indicate independence of cell function from the specific complement of cytoskeletal proteins

Summary In vertebrate tissue development a given cell differentiation pathway is usually associated with a pattern of expression of a specific set of cytoskeletal proteins, including different intermediate filament (IF) and junctional proteins, which is identical in diverse species. The retinal pigment epithelium (RPE) is a layer of polar cells that have very similar morphological features and practically identical functions in different vertebrate species. However, in biochemical and immunolocalization studies of the cytoskeletal proteins of these cells we have noted remarkable interspecies differences. While chicken RPE cells contain only IFs of the vimentin type and do not possess desmosomes and desmosomal proteins RPE cells of diverse amphibian (Rana ridibunda, Xenopus laevis) and mammalian (rat, guinea pig, rabbit, cow, human) species express cytokeratins 8 and 18 either as their sole IF proteins, or together with vimentin IFs as in guinea pig and a certain subpopulation of bovine RPE cells. Plakoglobin, a plaque protein common to desmosomes and the zonula adhaerens exists in RPE cells of all species, whereas desmoplakin and desmoglein have been identified only in RPE desmosomes of frogs and cows, including bovine RPE cell cultures in which cytokeratins have disappeared and vimentin IFs are the only IFs present. These challenging findings show that neither cytokeratin IFs nor desmosomes are necessary for the establishment and function of a polar epithelial cell layer and that the same basic cellular architecture can be achieved by different programs of expression of cytoskeletal proteins. The differences in the composition of the RPE cytoskeleton further indicate that, at least in this tissue, a specific program of expression of IF and desmosomal proteins is not related to the functions of the RPE cell, which are very similar in the various species.     

Evolutionary history of the northern leopard frog: reconstruction of phylogeny, phylogeography, and historical changes in population demography from mitochondrial DNA

This study uses a combined methodological approach including phylogenetic, phylogeographic, and demographic analyses to understand the evolutionary history of the northern leopard frog, Rana pipiens. We tested hypotheses concerning how (or if) known geological events and key features of the species biology influenced the contemporary geographic and genetic distribution of R. pipiens. We assayed mitochondrial DNA variation from 389 individuals within 35 populations located throughout the species range. Our a priori expectations for patterns and processes influencing the current genetic structure of R. pipiens were supported by the data. However, our analyses revealed specific aspects of R. pipiens evolutionary history that were unexpected. The phylogenetic analysis indicated that R. pipiens is split into populations containing discrete eastern or western haplotypes, with the Mississippi River and Great Lakes region dividing the geographic ranges. Nested clade analysis indicated that the biological process most often invoked to explain the pattern of haplotype position is restricted gene flow with isolation by distance. Demographic analyses showed evidence of both historical bottlenecks and population expansions. Surprisingly, the genetic evidence indicated that the western haplotypes had significantly reduced levels of genetic diversity relative to the eastern haplotypes and that major range expansions occurred in both regions well before the most recent glacial retreat. This study provides a detailed history of how a widespread terrestrial vertebrate responded to episodic Pleistocene glacial events in North America. Moreover, this study illustrates how complementary methods of data analysis can be used to disentangle recent and ancient effects on the genetic structure of a species.     

Osmotic and metabolic responses to dehydration and urea-loading in a dormant,terrestrially hibernating frog

Physiological responses to dehydration in amphibians are reasonably well documented, although little work has addressed this problem in hibernating animals. We investigated osmotic and metabolic responses to experimental manipulation of hydration state in the wood frog (Rana sylvatica), a terrestrial hibernator that encounters low environmental water potential during autumn and winter. In winter-conditioned frogs, plasma osmolality varied inversely with body water content (range 69–79%, fresh mass) primarily due to increases in sodium and chloride concentrations, as well as accumulation of glucose and urea. Decreased hydration was accompanied by a marked reduction in the resting rate of oxygen consumption, which was inversely correlated with plasma osmolality and urea concentration. In a separate experiment, resting rates of oxygen consumption in fully hydrated frogs receiving injections of saline or saline containing urea did not differ initially; however, upon dehydration, metabolic rates decreased sooner in the urea-loaded frogs than in control frogs. Our findings suggest an important role for urea, acting in concert with dehydration, in the metabolic regulation and energy conservation of hibernating R. sylvatica.