Spiroplasma infection causes either early or late male killing in <Emphasis Type="Italic">Drosophila</Emphasis>, depending on maternal host age

Symbiont-induced male-killing phenotypes have been found in a variety of insects. Conventionally, these phenotypes have been divided into two categories according to the timing of action: early male killing at embryonic stages and late male killing at late larval stages. In Drosophila species, endosymbiotic bacteria of the genus Spiroplasma have been known to cause early male killing. Here, we report that a spiroplasma strain normally causing early male killing also induces late male killing depending on the maternal host age: male-specific mortality of larvae and pupae was more frequently observed in the offspring of young females. As the lowest spiroplasma density and occasional male production were also associated with newly emerged females, we proposed the density-dependent hypothesis for the expression of early and late male-killing phenotypes. Our finding suggested that (1) early and late male-killing phenotypes can be caused by the same symbiont and probably by the same mechanism; (2) late male killing may occur as an attenuated expression of early male killing; (3) expression of early and late male-killing phenotypes may be dependent on the symbiont density, and thus, could potentially be affected by the host immunity and regulation; and (4) early male killing and late male killing could be alternative strategies adopted by microbial reproductive manipulators.     

Triterpene saponin hemi-biosynthesis of a leaf beetle’s (<Emphasis Type="Italic">Platyphora kollari</Emphasis>) defensive secretion

The adults of the leaf beetle Platyphora kollari (Chrysomelidae) are able to metabolise the oleanane triterpene β-amyrin (1) into the glycoside 3-O-β-d-glucopyranosyl-(1→4)-β-d-glucuronopyranosyl-hederagenin (2) that is stored in their defensive glands. The aim of this study was to test the hypothesis that oleanolic acid (3) is an intermediate in the conversion of 1 into 2 and to check whether the sequestration of pentacyclic triterpenes is selective in favour of β-amyrin (1). To this end, adults of P. kollari were fed with Ipomoea batatas leaf disks painted with a solution of [2,2,3-²H₃]oleanolic acid or [2,2,3-²H₃]α-amyrin and the secretion of their defensive glands analysed by HPLC–ESIMS. The data presented in this work indicated that the first step of the transformation of β-amyrin (1) into the sequestered glycoside 2 is its oxidation into oleanolic acid (3) and that this conversion is selective but not specific in favour of β-amyrin (1).     

Head injuries in child pedestrian accidents--in-depth case analysis and reconstructions

OBJECTIVE: The aim of this study was to investigate head injuries, injury risks, and corresponding tolerance levels of children in car-to--child pedestrian collisions. METHODS: An in-depth accident analysis was carried out based on 23 accident cases involving child pedestrians. These cases were collected with detailed information about pedestrians, cars, and road environments. All 23 accidents were reconstructed using the MADYMO program with mathematical models of passenger cars and child pedestrians developed at Chalmers University of Technology. The contact properties of the car models were derived from the European New Car Assessment Program (EuroNCAP) subsystem tests. RESULTS: The accident analysis demonstrated that the head was the most frequently and severely injured body part of child pedestrians. Most accidents occurred at impact speeds lower than 40 km/h and 98% of the child pedestrians were impacted from the lateral direction. The initial postures of children at the moment of impact were identified. Nearly half (47%) of the children were running, which was remarkable compared with the situation of adult pedestrians. From accident reconstructions it was found that head impact conditions and injury severities were dependent on the shape and stiffness of the car front, impact velocity, and stature of the child pedestrian. Head injury criteria and corresponding tolerance levels were analyzed and discussed by correlating the calculated injury parameters with the injury outcomes in the accidents. CONCLUSIONS: Reducing head injuries should be set as a priority in the protection of child pedestrians. HIC is an important injury criterion for predicting the risks of head injuries in child pedestrian accidents. The tolerance level of head injuries can have a considerable variation due to individual differences of the child pedestrians. By setting a suitable speed limit and improving the design of car front, the head injury severities of child pedestrians can be reduced.     

Experience,but not distance,influences the recruitment precision in the stingless bee <Emphasis Type="Italic">Scaptotrigona mexicana</Emphasis>

Recruitment precision, i.e. the proportion of recruits that reach an advertised food source, is a crucial adaptation of social bees to their environment. Studies with honeybees showed that recruitment precision is not a fixed feature, but it may be enhanced by factors like experience and distance. However, little is known regarding the recruitment precision of stingless bees. Hence, in this study, we examined the effects of experience and spatial distance on the precision of the food communication system of the stingless bee Scaptotrigona mexicana. We conducted the experiments by training bees to a three-dimensional artificial patch at several distances from the colony. We recorded the choices of individual recruited foragers, either being newcomers (foragers without experience with the advertised food source) or experienced (foragers that had previously visited the feeder). We found that the average precision of newcomers (95.6 ± 2.61%) was significantly higher than that of experienced bees (80.2 ± 1.12%). While this might seem counter-intuitive on first sight, this “loss” of precision can be explained by the tendency of experienced recruits to explore nearby areas to find new rewarding food sources after they had initially learned the exact location of the food source. Increasing the distance from the colony had no significant effect on the precision of the foraging bees. Thus, our data show that experience, but not the distance of the food source, affected the patch precision of S. mexicana foragers.     

The end of the fat dodo? A new mass estimate for <Emphasis Type="Italic">Raphus cucullatus</Emphasis>

A new mass estimate for the dodo (Raphus cucullatus), based on the lengths of the femur, tibiotarsus and tarsometatarsus, is attempted. The obtained mean mass is 10.2 kg, which is less than previous estimates based on other methods, which ranged from 10.6 to 21.1 kg, and much lower than the 50 lbs reported by a seventeenth-century eyewitness. The new estimated mass, which is similar to that of a large wild turkey, seems more realistic than previous ones and supports the hypothesis that contemporary illustrations of extremely fat dodos were either exaggerations, or based on overfed specimens. Pictures of “fat” dodos may also have been based on individuals exhibiting a display behaviour with puffed out feathers.     

Natural and man-made organobromine compounds in marine biota from Central Norway

Brominated organic pollutants were found in selected samples of mollusk tissue, fish liver, as well as in the eggs and livers of shag from three sites in Central Norway. More than 80 organobromines were identified owing to the defined isotope ratio acquired by GC/ECNI-MS. However, only a few peaks could be assigned to anthropogenic brominated flame retardants (polybrominated diphenyl ethers). Most of the organobromine compounds detected were unknown or halogenated natural products. The known halogenated natural products MHC-1 and TBA were abundant in all samples and usually between equally abundant, and up to 50 fold more concentrated than the major polybrominated diphenyl ether congener BDE 47. The halogenated natural products BC-2 (2-MeO-BDE 68) and BC-3 (6'-MeO-BDE 47), were on level with BDE 100 which was the second most abundant BDE congener in many samples. The previously identified natural polybrominated hexahydroxanthene derivatives (PBHDs) were detected for the first time in bird eggs. Being major contaminants in bird eggs, PBHDs were only present at low levels in bird liver from nestlings originating from the same clutch. Such differences were detected for several other major contaminants. One unknown tetrabromo compound particularly abundant in mussels from Munkholmen was studied by GC/MS and the molecular ion was detected at m/z 446. The abundance of the most important unknown compounds did not correlate with BDEs and they most likely represent halogenated natural products. This study supports that halogenated natural products have to be treated as serious contaminants of marine coastal waters. Our data suggest that their abundance is highest in habitats along the shoreline. Thorough examination of these compounds in environmental samples is an important task.     

Presence, biotransformation and effects of sulfophenylcarboxylic acids in the benthic fish Solea senegalensis

The presence of linear alkylbenzene sulfonates (LAS) and their degradation intermediates, sulfophenylcarboxylic acids (SPCs), with concentrations up to 100 ppb has been found in surface waters taken from the estuary of the river Guadalete (Cádiz, SW of Spain). Higher concentrations were found at the sampling site located adjacent to the discharge outlet of a wastewater treatment plant (WWTP). The concentrations decreased downstream to a few ppb as a result of dilution, sorption, and degradation processes, which were taking place along the estuary. Once the presence of both xenobiotics was confirmed in the environment, an in vivo assay was conducted to study their biotransformation and effects in the benthic fish Solea senegalensis. A flow-through system was employed, consisting of an exposure phase (120 h) with environmental levels of the surfactant (200, 500 and 800 microg/L of 2?C(10)LAS), followed by a depuration stage (72 h). The generation of SPCs has been quantified during these phases in both water and fish, with LAS biotransformation shown in all cases. The antioxidant enzymes catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), the phase II enzyme glutathione S-transferase (GST), and the phase III acid and alkaline phosphatases (AcP, ALP) were also estimated and utilized as biomarkers.     

Impact of dredging in a shallow coastal lagoon: Microtox Basic Solid-Phase Test, trace metals and Corophium bioassay

The aim of this work was to measure survival of the amphipod Corophium insidiosum and luminescence inhibition in the marine bacterium Vibrio fisheri on surface sediment samples collected from a shallow coastal lagoon (Pialassa Baiona, northern Adriatic Italian coast) before execution of dredging operations to deepen the main inner channel of the lagoon and restore the water circulation. Trace metal (Cd, Cu, Cr, Hg, Ni, Pb) concentrations, grain size and organic carbon matter content as loss of ignition were also measured. Toxicity testing with V. fisheri was carried out according to the Microtox Basic Solid-Phase Test (BSPT) protocol. The preliminary outcomes of this work show that: (a) the investigated area can be categorised as moderately degraded; (b) there is no evident spatial pattern in sediment toxicity and trace metal concentrations; (c) Microtox responses are not biased by sediment characteristics such as silt, clay and organic matter content.     

Transport and fate of mercury under different hydrologic regimes in polluted stream in mining area

Seepage from Hg mine wastes and calcines contains high concentrations of mercury (Hg). Hg pollution is a major environmental problem in areas with abandoned mercury mines and retorting units. This study evaluates factors, especially the hydrological and sedimentary variables, governing temporal and spatial variation in levels and state of mercury in streams impacted by Hg contaminated runo . Samples were taken during di erent flow regimes in theWanshan Hg mining area in Guizhou Province, China. In its headwaters the sampled streams/rivers pass by several mine wastes and calcines with high concentration of Hg. Seepage causes serious Hg contamination to the downstream area. Concentrations of Hg in water samples showed significant seasonal variations. Periods of higher flow showed high concentrations of total Hg (THg) in water due to more particles being re-suspended and transported. The concentrations of major anions (e.g., Cl??, F??, NO3?? and SO4 2??) were lower during higher flow due to dilution. Due to both sedimentation of particles and dilution from tributaries the concentration of THg decreased from 2100 ng/L to background levels (< 50 ng/L) within 10 km distance downstream. Sedimentation is the main reason for the fast decrease of the concentration, it accounts for 69% and 60% for higher flow and lower flow regimes respectively in the upper part of the stream. Speciation calculation of the dissolved Hg fraction (DHg) (using Visual MINTEQ) showed that Hg(OH)2 associated with dissolved organic matter is the main form of Hg in dissolved phase in surface waters in Wanshan (over 95%).     

生物炭添加和灌溉对温室番茄地土壤反硝化损失的影响

生物炭添加和灌溉是番茄地常用的田间管理措施,然而其对反硝化的影响还不清楚.本研究种植试验设置3个灌溉量水平分别为估算作物生育期需水量ET0的50%(W50%)、75%(W75%)、100%(W100%)和3个生物炭添加水平分别为B0(折合纯碳,0)、B25(折合纯碳,25 t·hm-2)、B50(折合纯碳,50 t·hm-2),在2014年和2015年番茄收获后,每个试验小区采集具有代表性的土样进行室内培养试验,采用乙炔抑制法来研究土壤的反硝化损失和不加乙炔研究N_2O的排放量.结果表明生物炭和灌溉量显著改变了土壤的理化性质.与B0相比,添加生物炭能够提高土壤全碳、全氮含量和pH值,降低铵态氮、硝态氮含量,而灌水量降低了土壤中全氮和全碳的含量.因此,与B0/W50%相比,B25/W75%和B50/W100%处理显著减少了反硝化损失量(P0.05).生物炭和灌溉量的交互作用对土壤无机氮含量和反硝化损失的影响均达到显著水平(P0.05),且对硝态氮的影响表现为灌溉量生物炭添加量两者交互作用,对铵态氮的影响表现为生物炭添加量灌溉量两者交互作用,对反硝化损失的影响表现为灌溉量生物炭添加量两者交互作用.反硝化损失量与土壤中无机氮含量、(CO_2-C)矿化量与N_2O排放量均呈正相关关系.不同生物炭添加量和灌溉量处理后明显影响了N_2O/DN(P0.05),培养结束时,各处理下的N_2O累积排放量/DN累积排放量差异较大,介于0.31%~1.88%.