Relationships between RNA content and egg production rate in Acartia bifilosa (Copepoda, Calanoida) of different spatial and temporal origin

To evaluate factors regulating RNA content (RNA, μg RNA female⁻¹) – egg production rate (EPR, eggs female⁻¹ day⁻¹) relationship and to develop a model for in situ egg production rate estimates for Acartia bifilosa, we (1) measured EPR and RNA in females sampled at geographically distant areas at varying temperature (T, °C), (2) determined environmental (station, season, and T), endogenous (prosome length (PL), mm and EPR) variables that influence RNA levels, and (3) explored a set of multiple regression models to predict EPR from RNA, PL, station, season, and T. Egg production experiments were carried out in spring and summer 2005 in the Gulf of Finland and in the western part of the northern Baltic proper. We found that up to 88% of the RNA variation could be explained by variations in PL, EPR, and season/T. In explaining the RNA variability, PL played a major role followed in order of importance by EPR and season/T. Further, PL, RNA, and season/T explained up to 53% of the variation in EPR, nearly half of which is explained by RNA alone. The effect of spatial origin was never significant, suggesting that the derived relationships are general for A. bifilosa inhabiting northern Baltic proper. An erratum to this article is available at .     

不同林龄马尾松（Pinus massoniana）人工林碳氮磷分配格局及化学计量特征

为了解长江上游低山丘陵区马尾松（Pinus massoniana）人工林生态系统的C、N、P分配格局及化学计量特征,本文采用时空互代的方法,在宜宾高县来复林区选取三种不同林龄（5年生幼龄林、14年生中龄林、39年生成熟林）,但立地条件相近、样地情况基本一致的马尾松（Pinus massoniana）人工林作为研究对象,对马尾松针叶、凋落物及土壤中的C、N、P含量及 w（C）？w（N）？w（P）化学计量特征进行测定和分析。结果表明,（1）C、N、P 含量均表现为针叶〉凋落物〉土壤,且在三个库之间差异显著;（2）林龄对针叶、凋落物、土壤的 C、N、P 及 w（C）？w（N）、w（C）？w（P）计量比均有显著影响。（3）土壤 C、N、P含量在成熟林中最高;针叶和凋落物的C含量在成熟林中最低,N、P含量则在中龄林中最高。（4）随林龄增加马尾松对N、P的利用效率降低,针叶、凋落物及土壤的w（C）？w（N）与 w（C）？w（P）均表现为下降。（5）马尾松针叶w（N）？w（P）比值在14.37~15.53之间,说明该地区马尾松人工林受N和P的共同限制,但林龄对N、P养分限制的影响不显著。为提高该区马尾松人工林的生产力,建议在人工林的抚育管理中要适当增加N肥和P肥,同时也可在马尾松人工林引入豆科固氮植物以提高地力。该研究将马尾松针叶、凋落物及土壤结合起来探究随林龄增长C、N、P养分元素的分配格局及化学计量特征的变化,有助于全面、系统地揭示马尾松人工林生态系统的养分循环,对指导马尾松人工林生产,调节和改善林木生长环境,提高系统的养分利用效率及林地生产力具有重要意义。     

Climate, habitat, and species interactions at different scales determine the structure of a Neotropical bat community

Climate, habitat, and species interactions are factors that control community properties (e.g., species richness, abundance) across various spatial scales. Usually, researchers study how a few properties are affected by one factor in isolation and at one scale. Hence, there are few multi-scale studies testing how multiple controlling factors simultaneously affect community properties at different scales. We ask whether climate, habitat structure, or insect resources at each of three spatial scales explains most of the variation in six community properties and which theory best explains the distribution of selected community properties across a rainfall gradient. We studied a Neotropical insectivorous bat ensemble in the Isthmus of Panama with acoustic monitoring techniques. Using climatological data, habitat surveys, and insect captures in a hierarchical sampling design we determined how much variation of the community properties was explained by the three factors employing two approaches for variance partitioning. Our results revealed that most of the variation in species richness, total abundance, and feeding activity occurred at the smallest spatial scale and was explained by habitat structure. In contrast, climate at large scales explained most of the variation in individual species' abundances. Although each species had an idiosyncratic response to the gradient, species richness peaked at intermediate levels of precipitation, whereas total abundance was very similar across sites, suggesting density compensation. All community properties responded in a different manner to the factor and scale under consideration.     

The implications of planting mode on cadmium uptake and remobilization in rice: Field experiments across growth stages

•Direct seeding (DS) method led to more distributed Cd in aerial parts of rice. •The Cd content was significantly higher in brown rice with planting mode of DS. •Using DS lessened the Fe plaque covering the root surface in all growth stages. •Transplantation mode should be considered as a priority in Cd-contaminated areas. Global rice production practices have gradually changed from a reliance on transplanting to direct seeding. Yet how this shift may alter cadmium (Cd) accumulation in rice is poorly known. Here we conducted field experiments with two rice genotypes cultivars that were planted using three methods: via direct seeding (DS), seedling throwing (ST), and manual transplanting (MT). Rice samples were collected during four growth stages. The formation and distribution of iron plaque were analyzed using DCB (dithionite-citrate-bicarbonate) extractions and observed under micro-XRF (micro X-ray fluorescence). The results revealed that, in each growth stage, DS rice was more apt to harbor Cd distributed in the plant’s aerial parts, and the Cd concentration of brown rice from DS was 21.8%–43.3% significantly higher than those from ST and MT at maturity stage (p<0.05). During the vegetative stages, the Cd uptake percentage was higher in DS than MT rice, and those plants arising from the DS method were capable of absorbing more Cd earlier in their growth and development. Conversely, using DS decreased the amount of iron plaque covering the root surface in every growth stage, especially in the critical period of Cd accumulation, such that the roots’ middle areas were distinguished by a near-complete absence of iron plaque, thus weakening its role as an effective barrier to Cd uptake from soil. Collectively, this study demonstrated that implementing the DS mode of planting will increase Cd’s distribution in the aboveground parts of rice, and heightening the risk of Cd contamination in grain.     

Responses to threat by female bobucks,<Emphasis Type="Italic"> Trichosurus caninus</Emphasis>, during different stages of offspring development

The costs of reproduction are widely recognised as a major selective force in the evolution of various behavioural and life-history characteristics. In particular, the behaviour of reproductively active animals is likely to change when breeding increases risk of predation. We investigated the effect of an experimentally derived threat on the vigilance and escape behaviour of female Trichosurus caninus with and without dependent offspring and at different stages of offspring development. Females with offspring showed a heightened response to the threat in comparison to females without offspring. In addition, females with offspring displayed a stronger response at earlier stages of their offsprings development.Communicated by P. Bednekoff     

The effect of low concentrations of phenol and ammonia on egg production rates,fecal pellet production and egg viability of the calanoid copepod Acartia clausi

Estimates of daily fecundity, hatching success and fecal pellet production are reported for Acartia clausi females exposed for 10 d to low levels of phenol and ammonia. Copepods were collected in 1991 and 1992 from a southern coastal area of the Mar Grande of Taranto (southern Italy). A reduction in egg numbers and fecal pellet production was observed for females after 8 d of exposure to 500 g l^-1 phenol concentration. Ammonia (120 g l^-1) produced a significant increment in egg production, but hatching success was reduced by about 50% after nine exposure days. A. clausi was more sensitive to ammonia than phenol at high concentrations (24-h LC₅₀ phenol-32.26 mg l^-1; 24-h LC₅₀ ammonia=0.91 mg l^-1). At low concentrations, only long-term exposure to phenol determined a reduction in fecundity.     

水稻不同生育期土壤砷形态分布特征及其生物有效性研究

采用田间原位试验和Tessier连续提取方法,在水稻（Oryza sativa L.）不同生育期研究了重金属复合污染高、中、低3个水平下的土壤砷的形态分布特征及其生物有效性。结果表明：在水稻不同生育期中,土壤各种形态的砷质量分数均表现为高污染水平土壤〉中等污染水平土壤〉低污染水平土壤;土壤中砷在水稻整个生育期均以残留态为主,占90%以上,交换态砷所占比例最低,不到0.5%;不同形态砷之间大都显著正相关,但是两种有效性较高的砷形态（交换态和碳酸盐结合态）与有机态砷之间的相关性较差;土壤砷的生物有效性表现为高污染水平土壤〉中等污染水平土壤〉低污染水平土壤,且随着水稻生育期的延长,土壤砷的生物有效性逐渐升高。     

The structure and sensitivity of the eye of different life history stages of the ontogenetic migrator Gnathophausia ingens

The structure and ultrastructure of the photoreceptors of several life history stages of the ontogenetically migrating lophogastrid crustacean Gnathophausia ingens were examined. The younger instars of this species live in a much brighter light field than the older instars, and this difference is reflected in differences in their visual systems. The shallowest free living individuals (instars 3 and 4) possess a superposition eye with almost no clear zone, which minimizes the light shared between ommatidia and reduces the sensitivity of the eye. A progression to superposition optics with a large clear zone, usually associated with night-active or deep-living species, occurs as the animals move deeper in the water column. Regional differences within the eye are also evident, with a largely nonexistent clear zone in the dorsal region and a large clear zone in the ventral region in the eyes of instar 5 animals, the first instar to move to deeper depths. The deepest living instars (10–12) possess superposition optics with a large clear zone throughout the eye, and are significantly more sensitive to light than the younger, shallower instars.     

海南儋州不同林龄橡胶林土壤碳和全氮特征

为研究热带人工林巴西橡胶树(Hevea brasiliensis)生态系统不同林龄土壤碳、全氮特征,对热带地区种植橡胶及其更新进行生态效益评估,文章分析了海南儋州地区幼林早期(2龄)、幼林晚期(7龄)、开割树(16龄)和老龄即将更新树(30龄)4种不同林龄的橡胶林土壤碳、氮质量分数垂直分布特征.结果如下,(1)不同林龄橡胶林胶园土壤有机碳质量分数存在极显著差异,其大小排列顺序为幼林晚期(7龄)>老龄即将更新树(30龄)>幼林早期(2龄)>开割树(16龄),各土壤层次土壤有机碳质量分数的空间垂直分布大体随着土层的深人而降低,其垂直分布的变异系数由大到小排列顺序为7龄幼林晚期(37.54%)>16龄开割树(26.48%)>30龄老龄即将更新树(24.44%)>2龄幼林早期(18.99%);(2)不同林龄橡胶林胶园土壤全氮质量分数存在显著差异,其大小排列顺序为幼林晚期(7龄)>幼林早期(2龄)>老龄即将更新树(30龄)>开割树(16龄),各土壤层次土壤全氮质量分数的空间垂直分布大体随着土层的深入而降低,其垂直分布的变异系数由大到小排列顺序为16龄开割树(34.32%)>7龄幼林晚期(30.98%)>30龄老龄即将更新树(21.09%)>2龄幼林早期(14.37%);(3)不同林龄胶林土壤碳氮(C/N)比存在极显著差异,其大小排列顺序为开割树(16龄)>老龄即将更新树(30龄)>幼林晚期(7龄)>幼林早期(2龄),各胶林土壤有机碳质量分数与土壤全氮质量分数之间均存在极显著线性正相关关系(R2≥0.5839,p<0.01).本研究可为研究热带土地利用与覆盖变化对全球碳循环及橡胶林生长碳氮耦合提供基础数据,为我国热区进行天然橡胶种植提供理论依据.     

Effects of ultraviolet radiation on different life cycle stages of the south Pacific kelps, Lessonia nigrescens and Lessonia trabeculata (Laminariales, Phaeophyceae)

The effects of exposure to ultraviolet radiation (UVR), 280–400 nm, in different life histories and development stages of the kelps, Lessonia nigrescens and L. trabeculata, collected in the south-east Pacific coast (30°S) were evaluated in the laboratory. Germination and viability (motile zoospores, settled spores), diameter of the primary cell of the gametophytes, percentage of female gametophytes, fertility and sporophytes production were measured after exposure to three radiation treatments (PAR; PAR + UVA; PAR + UVA + UVB). The effects of UVR in young sporophytes (diploid stage) were evaluated as changes in maximal quantum yield of chlorophyll fluorescence of photosystem II (PSII) (F _v/F _m). A significant decrease in all variables was observed for the treatment that included UVB (PAR + UVA + UVB) after 2 and 4 h of exposure, in relation to the control. The motile spores were more sensitive to UVR exposure compared to settled spores and gametophytes, suggesting that along with an increase in ontogenetic development; there is an increase in the tolerance to UVR. In addition, it was observed that early stages of the intertidal L. nigrescens were more tolerant to UVR compared to the subtidal L. trabeculata. These results allow initially to infer that UVR may be regarded as an important environmental factor influencing the upper limit of distribution of these species, mainly through its detrimental effects on the early stages of the life cycle.     

Robustness in life history of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) across large scales: effects of spatially and temporally induced variability on population growth

Understanding the demography and function of biotope-forming seaweed species is of great importance for the conservation of the target species itself, as well as its associated organisms. The brown seaweed Ascophyllum nodosum is fundamental for the functioning of coastal marine ecosystems in the North Atlantic. In this study, we use a data-based size-classified matrix model to investigate the temporal and spatial variability in demography, and the environment-specific stochastic sensitivity and elasticity, of two A. nodosum populations, one in western Sweden and one on the Isle of Man in the Irish Sea. A significant difference between the two populations was that the Swedish population had comparably low and more variable stochastic population growth rate (λ _s). This pattern was partly explained by the relatively high and varying mortality rates during extreme ice-years in Sweden, and by the lower survival of small individuals during all years. There were also fewer large individuals in Sweden due to lower transitions to the larger size-classes and higher probability of shrinkage. Sensitivities were analogous in the two populations, and showed a high selection pressure for increased individual growth. Elasticities were also similar, with the exception that survival of the smallest individuals (i.e., transition a _1,1), had a higher elasticity on the Isle of Man. Overall, the stochastic growth rate (λ _s) was most sensitive to proportional changes in loop- (i.e., survival within size-class) and, to some extent, growth-transitions in both study areas. These results show that structurally and demographically diverging A. nodosum populations may be similarly sensitive to changes in vital rates. This, in turn, indicates a plastic life history of A. nodosum that may cope with large environmental variability. The results further suggest that environmental change affecting the survival or growth of the larger, reproductive A. nodosum individuals could have severe and regional effects on the abundance and biomass of this species, with potential negative effects on the biodiversity of the associated communities.     

Descriptions and durations of premolt setal stages in female Dungeness crabs,<Emphasis Type="Italic"> Cancer magister</Emphasis>

For crustaceans with a well-defined annual molting season, such as adult female Dungeness crabs (Cancer magister Dana), setal molt staging can, in principle, be used to predict molting destiny of individual crabs. Size-specific predictions of molting probability could, in turn, be useful for estimating mortalities due to molting. Female Dungeness crabs were collected January–March 1997 at depths of 10–30 m off the California coast, USA (41°N). Intermolt stage A₁–C₄ and premolt stages D₀, D₁, D₁, D₁ and D₂ were described based on features of the branchial epipod. Laboratory experiments suggested that stage D₁ was the earliest stage beyond which eventual molting was inevitable so that molting destiny could be determined. Estimated mean number of days from the beginning of stage D₁ to molting was 85. Estimated individual stage durations, based on laboratory experiments, were 24, 51, –4, 18, and 20 days, respectively, for stages D₀, D₁, D₁, D₁, and >D₂. The estimated –4 days for stage D₁ suggests that this stage must be very brief and raises a question of its utility in designation of molt stages. Molt staging of three field samples, 300–600 crabs in each, collected prior to the 1997 annual molting season, indicated an increase in the size and frequency of crabs staged D₁ or later as the time to molt approached, although crabs of 150 mm carapace width and larger showed few signs of molt preparation. Because the duration of the molting season (approximately 120 days) for adult female C. magister in northern California exceeds the estimated maximum duration of reliable prediction of molting destiny (85 days), it does not appear that molt staging can be used to predict molting destiny in this population. However, the procedures that we have used in this paper for application to female C. magister might be used with success for other crustaceans if the duration of stages D₁ to molting exceeds the duration of the molting season, and furthermore may be used for describing temporal molting trends.Communicated by J.P. Grassle, New Brunswick     

The cost of parental care and egg cannibalism in the river bullhead,Cottus gobio L. (Pisces,Cottidae)

Summary Male river bullheads guard and care for egg masses during a single brood cycle every breeding season. A study of two bullhead populations demonstrated that nesting males show a strong reduction in food intake rate and that their physical condition deteriorates during parental care. The estimated weight loss for the average guarding male was 18.8% in one population and 13.5% in the other. This could in part be responsible for the peak of male mortality observed during the second part of the breeding season. A high incidence of egg cannibalism was observed in males guarding eggs. Analysis of the developmental stage of individual egg masses demonstrated that heterocannibalism is very rare in this species and that the observed rate of egg cannibalism is mainly due to guarding males preying upon their own eggs (filial cannibalism). In both populations the frequency of filial cannibalism was negatively correlated with the male's chance of getting other food items. The probability of a male cannibalizing its own eggs was also significantly influenced by the time elapsed since the beginning of parental care. The observed limited cannibalism of progeny in the river bullhead cannot be explained as a male's strategy for obtaining energy to be used in subsequent brood cycles, as suggested for other fishes which show filial cannibalism. Rather, it can be interpreted as a behaviour aimed at avoiding the risk of dying of starvation before the eggs hatch. The observed criteria of female mate choice, i.e. a preference for males in good physical condition and for males that already have eggs in their nests, are consistent with the prediction of Rohwer's filial cannibalism theory, although other hypotheses cannot be excluded.     

不同生育期镉胁迫对两种水稻的生长、镉吸收及糙米镉含量的影响

采用分阶段加镉水培试验,对杂交水稻“威优1126”和常规水稻“浙辐802”不同生育期对Cd胁迫的生长反应及其对Cd吸收、积累与分配特性进行了比较研究。结果表明,水稻对Cd胁迫的反应因生育期不同而异,幼穗分化之前(前期),镉毒害主要表现为降低光合生产力;幼穗分化至抽穗期(中期)主要抑制幼穗的分化与发育过程;抽穗之后(后期)主要阻碍碳水化合物和NP养分向穗部迁移和转化。从对产量形成影响来看,幼穗分化—抽穗期是水稻对Cd胁迫反应最敏感时期。水稻吸Cd速率为中期>后期>前期。糙米中Cd的含量受水稻植株吸收Cd的总量和茎叶Cd向籽粒转移效率的双重影响。杂交稻对Cd的吸收能力与常规水稻相近,但Cd在地上部分累积的比例比常规水稻高4.9%~21.8%,籽粒部分的镉与茎叶部分镉的比例比常规稻高49%~95%,糙米Cd含量比常规稻高33%~72%。从减产效应和对稻米卫生品质损害来看,杂交水稻对环境Cd污染比常规水稻更加敏感。     

The breeding biology of two sympatric species of tropical intertidal hermit crabs,Clibanarius chapini and C. senegalensis

A one-year study of breeding in the two intertidal hermit crabs Clibanarius chapini Schmitt and C. senegalensis Chevreux and Bouvier showed that both species maintain a high reproductive activity throughout the year. Brief low reproductive activities, found in both species, occurred in different months: C. chapini in November, C. senegalensis in May. While these drops cannot be attributed to any recognisable environmental factor, it is suggested that such pattern may result from competition between the two species. Sex-ratio studies indicated slightly more females than males in both species. The maximal size attained by males of both species is considerably greater than that of the females; in C. senegalensis this is very marked. It is suggested that it may be selectively advantageous for a female to attain a smaller maximal size since her brood must also be accomodated within the shell. As expected for continuously breeding species, recruitment of young into the population is also continuous.     

离子强度、pH对土壤胶体释放、分配沉积行为的影响

采用重力沉降法,根据司笃克斯(Stokes,1945)定律结合分速离心法提取两种粒径等级的自然土壤胶体样品.利用美国EPA批处理实验方法,进行一系列实验室静态吸附、解吸实验,并获取相应的动力学解离/沉积曲线以及热力学等温平衡解吸/吸附曲线.通过对土壤胶体释放/沉积速率、解离效率和解吸因数等行为因子的定量解析,描述自然土壤胶体的释放、稳定、沉积/分配动力学和热力学行为,考察土壤水溶液pH/离子强度、胶体粒径因素对土壤胶体释放、分配沉积行为的影响.实验结果表明,环境溶液pH的增大及离子强度的减小对土壤胶体的稳定和释放起促进作用,但对胶体向土壤颗粒中的沉积过程是不利的.pH和离子强度条件能够改变土壤胶体表面带电荷状态,改变土壤胶体与土壤介质表面吸附排斥作用力的大小,提高或降低土壤胶体与介质表面的碰撞接触效率,从而表现出土壤胶体在土壤介质中的沉积分配行为上的变化.粒径大小对土壤胶体的释放沉积行为影响明显.大粒径土壤胶体颗粒较小粒径颗粒更容易向土壤介质表面分配沉积.由此可知,土壤介质对土壤胶体持有和吸附的能力是与胶体颗粒粒径大小密切相关的,这主要是因为颗粒粒径大小能够有效的影响胶体颗粒与介质表面间的反应能量.土壤胶体沉积分配动力学曲线揭示,土壤胶体向土壤介质的分配过程是一个动态变化过程,土壤介质对土壤胶体的持留吸纳能力随时间而逐渐减弱.分配系数被证实是表征和分析土壤胶体沉积分配过程受环境物理化学因素影响的有效过程因子.