Endangered species: Deciding which species to save

Many species face extinction because preservation organizations do not have the resources to mount all of the interventions that are needed. Decision analysis provides techniques that can help managers of these organizations to make judgments about which species they will attempt to rescue. A formal analysis of the choices available to the US Fish and Wildlife Services' endangered species program with regard toIsotria medeoloides illustrates how the difficulties of making preservation decisions can be lessened.I. medeoloides is perhaps the rarest orchid in the United States. Little is known of the species' biology and less about effective management. Yet unless a preservation effort is mounted, the species will continue to be threatened by habitat destruction and botanical collecting. The analysis employs formal probabalistic techniques to weigh the utility of possible intervention strategies, that is, their likelihood of achieving different amounts of increase in the longevity of the species, and to balance these gains against their costs. If similar decision analyses are performed on other endangered species, the technique can be used to choose among them, as well as among strategies for individual species.     

手性农药丁氟螨酯对斑马鱼胚胎的选择性发育毒性

近年来丁氟螨酯（CYF）对非靶标生物的发育毒性已成为一个值得关注的问题,但其对水生生物的对映选择性效应尚不清晰.为评估丁氟螨酯对斑马鱼胚胎的对映选择性毒性,通过96 h的暴露试验,研究了梯度浓度的丁氟螨酯消旋体及对映体对斑马鱼胚胎的急性毒性.此外,试验还研究了丁氟螨酯对斑马鱼胚胎孵化率、卵黄囊水肿、心包囊水肿和身体弯曲的影响.根据急性毒性结果可知,毒性大小为S-CYF > Rac-CYF > R-CYF,其中S-CYF的毒性是R-CYF的2.3倍.72 hpf,500 mg·L^-1的S-CYF可显著诱导胚胎产生卵黄囊水肿（YSE）、体轴弯曲（CB）等畸形效应（p<0.05）,而Rac-CYF降低了斑马鱼胚胎的孵化成功率.在本研究中发育毒性效应结果与急性毒性结果一致,均为S-CYF > Rac-CYF > R-CYF,表明丁氟螨酯对斑马鱼胚胎存在显著的对映选择性发育毒性,研究结果为丁氟螨酯的环境风险评估提供了理论依据.     

Mechanisms enabling sperm economy in blenniid fishes

Sperm competition, cost of spermatogenesis and spawning frequency are known to influence ejaculate expenditure. Accordingly, males, particularly those with high reproductive costs, are expected to have evolved mechanisms enabling them to prudently allocate sperm, such as the fractioning of ejaculate expenditure or the semi-cystic type of spermatogenesis, hypothesised to favour the production of small ejaculates. In this study, we investigate sperm competition risk, ejaculate size and mode of ejaculate release in seven polygynous blenniid fish where males provide sole paternal care of eggs. In addition, we estimated the relative size of the two parts composing the male gonad, the strictly testicular (testicular lobules or testis) and the glandular (testicular gland), as the development of the latter is indicative of the level of semi-cystic spermatogenesis. In all the examined species, eggs were laid one by one, and the sperm expenditure at mating, evaluated as the total number of sperm released per mating, was parcelled out in several successive ejaculations, allowing males to adjust the release of sperm to the duration of egg deposition. In accordance with sperm competition theory, species experiencing higher sperm competition risk allocated more in sperm, both considering ejaculate size and ejaculate expenditure per mating. An increase in sperm expenditure was paralleled by the development of the testis at the expense of the testicular gland. Smaller species, whose males do not face sperm competition risk and fecundity is low, produced smaller ejaculates and exhibited a more developed testicular gland, supporting the hypothesis that a semi-cystic type of spermatogenesis is a mechanism allowing sperm economy.     

Dimethylsulphide and ocean–atmosphere interactions

Dimethylsulphide (DMS) is a trace sulphur gas found in most atmospheric and surface water samples, which is derived from dimethylsulphonioproprionate (DMSP). Although it has been extensively studied over the last 50 years, its natural production, consumption and cycling are still not completely understood. Until recently, DMS was believed to originate mainly from marine waters, but later studies have shown that estuaries and lakes are also an important source of DMS. DMS also originates from terrestrial plants such as maize, wheat and lichen, but it is not fully understood why. DMS is believed to have an important impact on the global environment by influencing factors such as the acidity of the atmosphere, cloud condensation nuclei (CNN) and solar insolation. The impact that humans have on the cycling of DMS and on its environmental impact is not well understood either. DMS is affected by temporal and geographical factors, as well as physical factors such as salinity and wind speed, yet when studied under El Niño conditions which modify these physical factors in vivo, there was found to be no fluctuation in the concentration of DMS in the water column. This review outlines our current state of knowledge on DMS.     

Rate of change of bod for milk in natural sea water

As part of a project to determine the fate of contaminated milk in the marine environment (Elliott et al ., 2001), the Biochemical Oxygen Demand (BOD) of unprocessed natural milk in sea water was followed in standard BOD bottles and in an open system. The best estimate for the BOD was ¨ 170,000 r mg - l m 1 although measurable effects could still be seen with dilutions up to one in a million. If incubated in the light, simulating summer conditions, the algae produced oxygen and offset some of the loss through bacterial degradation thereby reducing any slump in oxygen. There was also a "nutrient effect" where the presence of milk increased the oxygen production at low concentrations in sea water. In an open system akin to a slick being dispersed, the change in BOD was exponential after an initial activation period. The length of this activation period was greater in more concentrated mixtures of milk and sea water. These results have been utilised in a model to determine the best strategy for disposing of contaminated milk (Elliott et al ., 2001).