Sulfate-Reducing Bacteria in Gypsum Karst Lakes of Northern Lithuania

Microbiological studies were performed in three small gypsum karst lakes in northern Lithuania, most typical of the region. Samples were taken in different seasons of 2001. The conditions for microbial growth in the lakes are determined by elevated content of salts (from 0.5 to 2.0 g/l), dominated by SO ₄ ^2? and Ca²⁺ ions (up to 1.4 and 0.6 g/l, respectively). The elevated sulfate concentration is favorable for sulfate-reducing bacteria (SRBs). Summer and winter stratification gives rise to anaerobic water layers enriched in products of anaerobic degradation: H₂S and CH₄. The lakes under study contain abundant SRBs not only in bottom sediments (from 10³ to 10⁷ cells/dm³) but also in the water column (from 10² to 10⁶ cells/ml). The characteristic spatial and temporal variations in the rate of sulfate reduction were noted. The highest rates of this process were recorded in summer: 0.95–2.60 mg S^2?/dm³ per day in bottom sediments and up to 0.49 mg S^2?/l per day in the water column. The maximum values (up to 11.36 mg S^2?/dm³) were noted in areas where bottom sediments were enriched in plankton debris. Molecular analysis of conservative sequences of the gene for 16S rRNA in sulfate-reducing microorganisms grown on lactate allowed them to be identified as Desulfovibrio desulfuricans.     

中国洞穴甲壳动物多样性及其对洞穴环境的适应性

简要阐述了洞穴环境的研究现状以及洞穴动物的生态特征,初步探讨了中国洞穴甲壳动物的形成过程、多样性、地理分布以及对洞穴环境的适应性。截止到2008年10月,我国已记录的洞穴甲壳动物(主要指十足目虾类和端足目钩虾类)共有33种,分别隶属6科10属,主要分布在贵州省、广西省等喀斯特洞穴密集地区。洞穴甲壳动物由于长期生活在洞穴的黑暗带,食物匮乏,水温恒定,CO2浓度过高,且O2浓度相对较少的环境中,其在形态结构、消化系统、生理及行为等方面逐渐表现出与地表甲壳动物不同的适应性特征。如:眼缺失、体无色、触角和附肢显著增长、新陈代谢减慢、代谢率小,昼夜节律降低,不能调节体温,生活步调放慢,寿命长,发育周期长等。     

喀斯特石漠结皮细尖鳞叶藓的吸水机制及耐旱适应性

生物结皮是由隐花植物和相关土壤微小生物与表层土壤颗粒胶结而形成的复合体,与维管束植物覆盖一样,它是干旱区地表的重要覆盖类型。苔藓是荒漠植被演替过程中常见的一类先锋植物,同时也是生物结皮中生物量最大的2个类群之一。研究了结皮细尖鳞叶藓的吸水机制和耐旱适应性。结果表明:细尖鳞叶藓最大吸水量和持水率分别达到干重的9.74倍和700%以上,动力学总吸水过程的表观Km值和Vmax值分别为21.67g、10.42g·g-·1DW·min-1,外吸水过程为28.91g和8.56g·g-·1DW·min-1,内吸水过程为43.18g和1.76g·g-·1DW·min-1。可溶性糖含量从142.6mg·g-·1DW(CK)上升到344.3mg·g-·1DW,增长近2.4倍,而游离脯氨酸积累微弱。抗氧化酶SOD活性变化不明显,在0.04U·g-·1FW上下浮动;POD活性在PEG6000胁迫浓度在20%之前呈大幅度上升状态,以后趋于缓和,30%时达最高的131U·g-·1min-·1FW,增加近2倍;CAT活性的变化情况与POD变化趋势相同,但变化量较小。膜脂过氧化指标MDA先略有升高又逐步回落,说明细尖鳞叶藓抗氧化酶系统利用提高POD和CAT活性清除SOD在清除超氧阴离子自由基过程中产生的H2O2。因此,在喀斯特石漠化缺少土壤、极度干旱且保水能力弱的环境区域,结皮藓类植物以其特有的吸水特征、持水功能和抗旱机制等生态功能在石漠化治理、退化生态系统的恢复中具有十分重要的作用。     

Description of a new species of Phylloscopus warbler from Vietnam and Laos

A new species of Phylloscopus warbler, which we name Phylloscopus calciatilis Limestone Leaf Warbler, is described from central and northern Vietnam and central and northern Laos; it probably also breeds in southernmost China. In morphology, the new species is very similar to Sulphur-breasted Warbler Phylloscopus ricketti , but it is smaller with a proportionately larger bill and rounder wing. Its song and calls are diagnostic. Based on mitochondrial and nuclear DNA, the new species is most closely related to P. ricketti and Yellow-vented Warbler Phylloscopus cantator , and it is inferred to be sister to the latter. The mitochondrial divergences between these three species are at the low end of the variation found in other species of Phylloscopus and Seicercus warblers, but greater than in other taxa generally treated as subspecies. Possible introgressive hybridization between the new species and P. ricketti is discussed, but more data are needed to establish whether it does occur and, if it does, to what extent. The new species appears to have a restricted breeding range in limestone karst environments, where it is locally common and therefore not under any immediate threat. In view of the recognition of the new species, all previous records of P. ricketti sensu lato need to be re-evaluated.     

Activity following arousal in winter in North American vespertilionid bats

• 1 Many bat species hibernate to conserve energy during winter and like all hibernators they commonly arouse. During these arousals, some bats may undertake activities away from the hibernation site. Systematic ecological studies of the frequency and purpose of winter activity in temperate zone bats of North America are rare and much of the literature involves observations of single individuals or unmarked populations.
• 2 We review the available literature on winter activity among North American vespertilionid bats to highlight the paucity of data on this subject and to stimulate future research. Due to the lack of repeated, systematic studies on most North American species, the conclusions drawn are general or pertain only to parts of the geographical range of any species.
• 3 We suggest that winter activity is ubiquitous among temperate zone bats, but the degree and purpose of activity varies greatly between and within species. In general, cave‐dwelling bats tend to be relatively inactive compared with tree and foliage roosting bats during winter.
• 4 Cave‐dwelling and tree cavity‐dwelling species do not appear to feed, but they do drink and occasionally copulate during the hibernation period. Species that hibernate in foliage or leaf litter are the most active species during winter and may feed and drink throughout winter, although they probably do not copulate because of their solitary nature.
• 5 We encourage researchers to conduct studies on all aspects of winter activity for North American vespertilionids across wide latitudinal and altitudinal gradients. We suggest studies in the near future be focused on estimating the energetic costs and benefits of winter activity through determination of the frequency and intensity of winter feeding activity and more thorough examinations of movements within and among caves. Studies on common, wide‐ranging species have the potential to illuminate large‐scale patterns and differences and should be favoured over studies on rarer species.

     

Ultrastructure of the peduncular aesthetascs of Speleonectes tanumekes (Crustacea, Remipedia) in comparison with crustaceans from stressful environments

Abstract. Osmotic stress associated with the freshwater environment and desiccation stress associated with the terrestrial environment may have a shortening effect on the length of the innervation of crustacean aesthetascs. Physical stress of the littoral environment may have a similar effect on the length of the cuticular portion of aesthetascs. The aesthetascs of crustaceans that inhabit these environments share a similar ultrastructural feature, which may help animals cope with these environmental stresses. This ultrastructural feature, the position of the basal bodies proximal to the lumen of the aesthetasc, is absent from the aesthetascs of crustaceans that occur in the typical marine environment. Interestingly, the ultrastructural feature associated with these stressful habitats is present in the peduncular aesthetascs of the remipede Speleonectes tanumekes , even though the environmental stresses that may invoke the reduction of aesthetascs are absent in the marine-cave environment where this animal occurs. The importance of the sensitivity of aesthetascs for survival in this lightless environment may result in a selective pressure that favors basal bodies to be positioned proximal to the lumen of the aesthetasc.     

A carboniferous chondrichthyan assemblage from residues within a Triassic karst system at Cromhall quarry,Gloucestershire, England

Abstract. Sixteen different Lower Carboniferous (Tournaisian Courceyan to Chadian age, Mississippian) chondrichthyan teeth types have been extracted from Triassic erosional/aeolian fills in shallow karst systems found in the limestone quarry at Cromhall, Gloucestershire, England. These Carboniferous teeth have been found within a much larger assemblage of disarticulated bones and teeth belonging to small late Triassic terrestrial reptiles, for which Cromhall quarry is famous. The Carboniferous teeth are derived fossils, released during subaerial dissolution of the surrounding limestones. Owing to low specimen numbers and uncertainty of intraspecific character, 10 types of teeth are left in open nomenclature, although it is likely they represent new taxa. They belong to Jalodus, Ctenacanthiformes, Protacrodus, Orodus, Chomatodus, Petalodontidae, Euchondrocephali?, Helodus and Psephodus. A new genus and species, Cromhallia parvunda, of indeterminate phylogenetic relationships, is also erected. The assemblage includes also an identified suite comprising Thrinacodus ferox, Bransonella cf. nebraskensis and Stethacanthus cf. altonensis. The identification of all fish teeth found in the Cromhall assemblages as derived fossils from the Carboniferous removes any ambiguity regarding the fully terrestrial nature of the late Triassic fauna preserved in the residue‐bearing karst systems.     

Fish migrate underground: the example of Delminichthys adspersus (Cyprinidae)

Complex aquatic systems of karst harbour a rich but little‐investigated biodiversity. In Croatia and Bosnia–Herzegovina karst, temporal springs are inhabited by a group of minnow‐like fishes that retreat to the associated ground water during dry seasons and spend several months underground. The most abundant species in this group is Delminichthys adspersus (Heckel 1843), which also has the most fragmented distribution range. To determine the population composition and dispersal patterns, and to detect potential underground migration, a large genetic data set comprising 544 specimens of D. adspersus covering most of its distribution area was analysed. Analysis of mitochondrial cytochrome b sequences (～1000 bp) and eight microsatellite loci showed that D. adspersus comprises at least three subpopulations with gene flow occurring among them. Coalescent‐based analysis revealed a complex migration pattern, with several unidirectional dispersal paths, including between temporal springs that share no surface connection. The results of this study suggest the existence of recurrent underground migration of fish in a karst environment and demonstrate the complexity of its hydrological network. The findings are relevant to conservation strategies for endemic karst organisms and karst ecosystems as a whole.     

热带喀斯特森林常绿和落叶榕树的水力特征和水分关系与抗旱策略

以热带喀斯特地区的直脉榕(Ficus orthoneura)和豆果榕(F.pisocarpa)为实验材料,研究了常绿和落叶树木枝条和叶片的解剖结构特征、光合水分特征和耐旱性的差异,目的在于探讨不同生活型榕树适应干旱生境的策略.直脉榕和豆果榕的叶片都有两层栅栏组织、游离状的海绵组织和钟乳体等旱生结构,同时叶片角质层蒸腾速率(gmin)和气孔导度(gs)相对较低.但与落叶的豆果榕相比,常绿的直脉榕的枝条木质部失去50％传导率的水势(P50)和gmin更低,表现出更保守的水分利用策略.总体上,两种榕树都表现出了对喀斯特干旱生境的良好适应,但是它们的适应策略表现出一定的差别.豆果榕通过落叶度过旱期,而直脉榕在结构和功能上比豆果榕更耐旱.抗旱策略和水分利用策略的不同导致两种榕树的生态位分异,减少了彼此间的水分竞争,有利于它们在喀斯特生境中共存.     

喀斯特峰丛洼地不同森林表层土壤有机质的空间变异及成因

基于动态监测样地(200 m×40 m)的网格(10 m×10 m)取样,以农作区为对照,用地统计学方法研究了喀斯特峰丛洼地人工林、次生林和原生林3类典型森林生态系统表层土壤(0—15 cm)有机质的空间变异,通过主成分分析和相关分析,探讨了其生态学过程和机制。结果表明:喀斯特峰丛洼地土壤有机质很高,沿着农作区-人工林-次生林-原生林的恢复梯度,土壤有机质显著提高,变异系数逐步增大;农作区和3类森林土壤表层有机质均具有良好的空间自相关性;农作区试验半变异函数C0/(C0+C)值为26.5%,呈中等程度的空间相关性;3类森林的C0/(C0+C)值为9.0%—22.6%,呈强烈的空间相关性;农作区和人工林土壤有机质呈单峰分布,次生林呈凹型分布,原生林呈凸型分布;不同森林的主导因子不同,农作区的主导因子为主要土壤养分,人工林为地形和物种多样性,次生林为森林结构和物种多样性,原生林为地形和物种多样性,且同一因子在不同森林与土壤表层有机质的正负作用关系和相关程度也不同。因此,农作区和3类森林应根据其土壤表层有机质的空间变异及主要影响因子制定相应的固碳措施。