High precision during food recruitment of experienced (reactivated) foragers in the stingless bee<Emphasis Type="Italic"> Scaptotrigona mexicana</Emphasis> (Apidae,Meliponini)

Several studies have examined the existence of recruitment communication mechanisms in stingless bees. However, the spatial accuracy of location-specific recruitment has not been examined. Moreover, the location-specific recruitment of reactivated foragers, i.e., foragers that have previously experienced the same food source at a different location and time, has not been explicitly examined. However, such foragers may also play a significant role in colony foraging, particularly in small colonies. Here we report that reactivated Scaptotrigona mexicana foragers can recruit with high precision to a specific food location. The recruitment precision of reactivated foragers was evaluated by placing control feeders to the left and the right of the training feeder (direction-precision tests) and between the nest and the training feeder and beyond it (distance-precision tests). Reactivated foragers arrived at the correct location with high precision: 98.44% arrived at the training feeder in the direction trials (five-feeder fan-shaped array, accuracy of at least ±6° of azimuth at 50 m from the nest), and 88.62% arrived at the training feeder in the distance trials (five-feeder linear array, accuracy of at least ±5 m or ±10% at 50 m from the nest). Thus, S. mexicana reactivated foragers can find the indicated food source at a specific distance and direction with high precision, higher than that shown by honeybees, Apis mellifera, which do not communicate food location at such close distances to the nest.     

First-trimester biochemical and molecular diagnoses using chorionic villi: High accuracy in the U.S. collaborative study

The accuracy of biochemical and molecular prenatal diagnoses using chorionic villi as the fetal source was assessed by seven centres participating in the NICHD collaborative study on the safety and accuracy of chorionic villus sampling (CVS) and amniocentesis. Of 601 pregnancies studied, biochemical methods were used to determine the diagnosis in 283 fetuses at risk for 35 different metabolic disorders. Fifteen different lysosomal storage diseases accounted for 81 per cent of the biochemical prenatal diagnoses performed, with 57 per cent of these pregnancies at risk for Tay-Sachs disease. No errors were made in the biochemical diagnoses that predicted affected or unaffected fetuses. However, the diagnoses of certain disorders (e.g., mucopolysacchariodosis type IH, metachromatic leukodystrophy, and Krabbe disease) occasionally required confirmatory studies in cultured amniocytes because the enzyme results were inconclusive in direct and/or cultured villi or due to the presence of a pseudodeficiency allele. Of these, only the diagnosis of a fetus at risk for Krabbe disease remained inconclusive after special studies to discriminate between mutant and pseudodeficiency alleles. Recombinant DNA techniques were used to predict the diagnosis of 318 fetuses at risk for 16 different disorders in which the defective disease gene could be detected either directly or by linkage analysis to a nearby polymorphic marker. Of these, 32 per cent were for haemoglobinopathies, 25 per cent for cystic fibrosis, 24 per cent for Duchenne or Becker muscular dystrophy, and 7 per cent for haemophilias. Pregnancies at risk for known disorders with specific molecular lesions (e.g., sickle cell disease) were accurately diagnosed in direct and/or cultured villi. Diagnoses requiring analyses with closely linked polymorphic markers were occasionally uninformative or inconclusive. Maternal contamination was not reported in any biochemical or molecular-based diagnosis. These studies document the high accuracy and rapidity of both biochemical and mutation-specific prenatal diagnoses with direct and cultured chorionic villi.     

市场、人口动态和沿海生态系统

我们的议题是从3个方面:生活、全球化和公共财产及其外在因素,通过关注环境资源和生态系统服务的价值,来讨论市场是如何影响沿海生态系统内人口和环境关系的.由于在考察市场是如何控制人口统计和环境结果时没有新的方法,所以我们建议通过综合观察沿岸和海洋的健康状态,并提出相应的见解,使问题的焦点集中在面临重大危机的沿岸生态系统上.     

Short-term variability in the photosynthetic activity of microphytobenthos as detected by measuring rapid light curves using variable fluorescence

Short-term variability in the photosynthetic activity of microphytobenthos assemblages was studied by measuring chlorophyll fluorescence rapid light curves (RLC), using pulse amplitude modulated (PAM) fluorometry. Measurements carried out on undisturbed samples under dark–light cycles revealed large diel oscillations in both the initial slope of the RLC () and in the maximum relative electron transport rate (ETR_m). Short-term variations in RLC parameters were also observed, closely following changes in incident photon irradiance (E). Increases in irradiance were followed by decreases in and increases in ETR_m, resulting in significant correlations between the light-saturation parameter E_k and E. These results were interpreted as resulting from the onset of reversible energy-dissipating, non-photochemical quenching mechanisms and of compensatory high light-induced activation of carbon metabolism activity. Short-term RLC variability was shown to result mainly from physiological causes and to be detectable only by using short (10–20 s) light steps during RLC construction. Dark-adapted samples kept under constant conditions exhibited apparently endogenous rhythms in RLC parameters and in the maximum quantum yield, F_v/F_m, coincident with vertical migratory movements occurring during subjective photoperiods. These fluctuations appeared to result from the interaction between migratory rhythms and the physiological responses, and from the endogenous activation of processes affecting both the efficiency of energy transfer from light-harvesting antennae to the photosystem II (PSII) reaction centres or from non-radiative pathways (F_v/F_m, ) and the reactions downstream of PSII (ETR_m).Communicated by M. Kühl, Helsingør