Demography of the land snail Tikoconus (Tikoconus) costaricanus (Stylommatophora: Euconulidae) in tropical low montane and premontane forests, Costa Rica

Introduction: Ecology and natural history of neotropical land snails is almost unknown. Objetive: In this paper, I analyse the population dynamics of Tikoconus (Tikoconus) costaricanus Barrientos, an understory endemic euconulid. Methods: I compared T. costaricanus' demography patterns in tropical montane forests in central Costa Rica in three habitats with different restoration techniques: a mature forest, a secondary forest and a Cuppressus lusitanica plantation. I collected data in three month periods during a year. I analysed population size in relation with habitat, sampling date, leaf litter humidity, depth and quantity; and specimen size in relation with habitat and sampling date. I also kept some specimens in terraria and described part of their natural history. Results: The species is more abundant in mature forest (Ø = 0.174 ind/m2). The number of specimens in each habitat was constant throughout the year (Kruskall-Wallis = 2.0118, p = 0.57, NS) and hatching occurs in the middle and last months of the rainy season (Kruskall-Wallis = 17.3061, P = 0.00061, **). Number of specimens is related with leaf litter humidity (Spearman correlation, r = 0.3524, n = 232, P < 0.001, **), quantity (Spearman correlation, r = 0.3922, n = 232, P < 0.001, **) and depth (Spearman correlation, r = 0.2543, n = 232, P < 0.001, **). This relationship is explained by the high and stable humid environment provided by leaf litter. Some specimens migrate from foliage to leaf litter during the drier months. Eggs (Ø = 1mm) are laid on moss or soil and the young spend the first 2 or 3 weeks of their life on moss. Egg masses are small (Ø = 4 eggs), and shells look bubbly. Egg development time (20 days) was longer than in other tropical species. Adult pigmentation appears around two months after hatch. In the only case observed, egg laying began 5 months after hatching and the specimen lived 9 months. Conclusions: Restorations techniques should consider leaf litter features in order to protect endemic neotropical humid dependent diversity.

Introducción: La ecología y la historia natural de los moluscos terrestres neotropicales es casi desconocida. Objetivo: En este artículo analicé la dinámica poblacional de Tikoconus (Tikoconus) costaricanus Barrientos, una especie endémica que habita el sotobosque del centro de Costa Rica. Métodos: Comparé los patrones demográficos de la especie en un bosque tropical montano en tres hábitats con diferentes estrategias de restauración: un bosque maduro, un bosque secundario y una plantación de Cuppressus lucitanica. Recolecté datos en periodos de tres meses durante un año. Analicé el tamaño de la población en relación : hábitat, fecha de muestreo, humedad, profundidad y cantidad de la hojarasca. También analicé el tamaño de los especímenes en relación al hábitat y fecha de muestreo. Mantuve algunos especímenes en terrarios y describí parte de su historia natural. Resultados: La especie fue más abundante en el bosque maduro (Ø = 0.174 ind/m2). La cantidad de especímenes en cada hábitat fue constante a lo largo del año (Kruskall-Wallis= 2.0118, P = 0.57, NS) y la eclosión se presenta en la mitad y últimos meses de la estación lluviosa (Kruskall-Wallis = 17.3061, P = 0.00061, **). La cantidad de especímenes estuvo relacionada con la humedad del ambiente que provee la hojarasca. Durante los meses más secos algunos especímenes migran del follaje a la hojarasca. Los huevos (Ø = 1 mm) son depositados en el musgo y en el suelo y los jóvenes pasan las primeras 2 o 3 semanas de su vida en el musgo. Las masas de huevos son pequeñas (Ø = 4 huevos) y los huevos se ven como construidos de burbujas. El tiempo de desarrollo de los huevos (20 días) fue más prolongado que en otras especies tropicales. La pigmentación del adulto aparece alrededor de dos meses después de la eclosión. En el único caso observado la ovoposición empezó a los 5 meses después de la eclosión y el espécimen vivió hasta los 9 meses. Conclusiones: Las técnicas de restauración deben considerar las características de la hojarasca con el fin de proteger la biodiversidad neotropical endémica dependiente de la humedad del ambiente.

Study on Mechanism of Arsenic Tolerance in Duckweeds from Lead-Zinc Mine by Synchrotron Radiation X-ray Fluorescenceand X-ray Absorption Near Edge Structure Spectrometry / 分析化学

Aquatic plant duckweed can enrich high concentration of arsenic, it is thus used as the representative of phytofiltration.The mechanism of arsenic tolerance in duckweeds has received much concern.In this study, synchrotron radiation X-ray fluorescence (SRXRF) and X-ray absorption near edge structure (XANES) techniques were used to study the micro-distribution and speciation of arsenic in natural As-rich duckweed from lead-zinc mine.Two monolithic duckweeds, FP1 and FP2, were analyzed by micro SRXRF, setting single point scan time and spot size were 5 s, 70 μm×80 μm and 2 s, 100 μm×100 μm respectively.Six points of FP2 were selected and analyzed by micro XANES in energy range of 11.81-11.96 keV.Pressed-pellet duckweed was analyzed by bulk XANES in energy range of 11.67-12.27 keV.The result showed that As(Ⅲ) was the major speciation of duckweed from bulk XANES and micro-XANES data.SRXRF micro analysis showed that arsenic had significant vein distribution in duckweed, and was not spread into the photosynthetic mesophyll within certain concentration, which may reduce the leaf toxicity triggered by arsenic.This vein distribution may play a role in arsenic tolerance in duckweed.

Distribution and Speciation of Lead in Moss Collected from a Lead-Zinc Mining Area by Micro-X-Ray Fluorescence and X-Ray Absorption Near Edge Structure Analysis / 分析化学

Moss has high tolerance and accumulating capacity to heavy metal.In this study, the distribution of heavy metal elements in moss sampled from lead-zinc mine was analyzed by X-ray fluorescence spectrometry.The speciation of lead was analyzed by X-ray absorption near-edge spectroscopy.Research showed that the contents of Pb, Zn, Cd and As in the moss of the mining area were extremely high, and their maximum concentration were 1.06 mg/g , 1.23 mg/g, 30.5 μg/g, 13.2 μg/g, respectively.Besides, the shoots especially the new tissue of the moss were the major sites for accumulation and storage of heavy metals.The micro-distribution characteristics varied among Hypnum plumaeforme and Brachytheciumprocumbens, indicating the difference of different species of moss in absorption pathway, accumulation and tolerance mechanisms for heavy metal.Linear combination fitting results indicated that the main lead speciation in moss was lead phosphate (78%) and lead oxide (22%), which suggested that the precipitation of lead phosphate might be the main mechanism of tolerance for moss.

A Study on Distribution and Chemical Speciation of Lead in Corn Seed Germination by Synchrotron Radiation X-ray Fluorescence and Absorption near Edge Structure Spectrometry / 分析化学

Synchrotron radiation X-ray fluorescence analysis technology (SRXRF) can effectively reduce the detection limit for the determination of heavy metal elements, especially suitable for in situ nondestructive analysis of biological samples with low contents. By corn seed germination test, and combining with SRXRF technology, the effects of Pb on corn seed germination and Pb micro-distribution in the corn seed were studied. X-ray absorption near edge structure (XANES ) technique was used to analyze the Pb chemical speciation in different parts of corn seed. The above experiment was taken to understand the absorption and transformation mechanism of Pb by corn seeds. Results showed that germination rate, bud length and root length decreased with increased Pb contents. The analysis of variance showed that P-value of the germination rate, bud length and root elongation of corn seeds which were exposed to different concentration of Pb were 2. 0×10-3, 1. 4×10-4 and 2. 39×10-8, which were all less than 0. 01, therefore there were highly significant differences during these three indicators and the content of Pb. In addition, the inhibition effect on root growth was greater. SRXRF analysis results showed that Pb was mainly enriched in episperm and embryo, which would inhibit embryonic develop into bud and root. The Pb-LⅢ(13035 eV) XANES spectra of all samples include of root, shoot and the different part of seed were the same, they were the same speciation. Linear combination fitting results indicated that the lead phosphate chloride and lead stearate accounted for 74 . 3 %and 24. 2 % respectively, which suggested that the main Pb speciation of corn was lead phosphate chloride which deposited inside of corn, and a few combined with carboxylic to form the organic lead.

Reflection on the Micro-Distribution of Chinese Organ Transplants Resources / 中国医学伦理学

Great achievements have been made in Chinese organ transplant technology and development.However,the organ supply is far less than demand in current condition.Therefore,the distribution of organ transplantation resources has become a focus of attention,in which the micro-distribution of organ transplantation resources is of urgent importance.Due to the imperfect mechanism in current micro-allocation of organ transplants resources in China,a novel micro-allocation mechanism with better ethical justification and social recognition is to be established.