Suppression of sexual behavior in male Japanese medaka (Oryzias latipes) exposed to 17beta-estradiol

Mating pairs of Japanese medaka (Oryzias latipes) received 17beta-estradiol (E2; dose, 3 and 30 microg/g body weight daily) in their diet and E2-free diet (control) for two weeks. The effect on reproductive success was assessed in the mating pairs, and sexual and nonsexual behaviors in the male were quantified. The fecundities of the E2-treated groups were reduced significantly (p < 0.05) compared with those of control, and the sexual behaviors (following, dancing, floating, and crossing) of male fish in response to prostaglandin F2alpha (PG)-injected E2-unexposed females were suppressed dramatically. While the fertility of spawned eggs and the frequencies of the nonsexual behaviors of resting and swimming in a straight line performed by male were unchanged in E2-exposed groups. Therefore, sexual behavior in male may be linked with reproductive success in mating pair of madaka exposed to E2. This assay for sexual behavior using PG may provide a useful tool for assessing the effect of endocrine-disrupting chemicals.     

Are direct developers more locally adapted than planktonic developers?

The hypothesis that populations of direct developers exhibit greater geographic differentiation in life history features than populations of planktonic developers, was tested with two species of grazing snails of the genus Littorina from 1986 to 1987. Littorina sitkana (direct developer) and L. scutulata (planktonic developer) coexist on sun- and wave-sheltered beaches from Alaska to Oregon, USA. Seasonal patterns in growth, survival and reproduction were monitored for samples from four geographically separated populations of each species grown in population cages at a common site, Friday Harbor, Washington, USA. The environmental and population effects on growth in the two species were determined in a four-way reciprocal transplant experiment with the same populations. Both the direct and planktonic developers exhibited geographic differentiation in life history features. Differentiation in the direct developer occurred over distances shorter than 30 km, while differentiation in the planktonic developer occurred over the 500 km distance examined (greater than their larvae would likely travel).     

Caste-fate determination primarily occurs after adult emergence in a primitively eusocial paper wasp: significance of the photoperiod during the adult stage

Independent-founding paper wasps constitute a major group of primitively eusocial insects, and when caste-fate determination occurs in temperate species of these wasps, particularly regarding whether it occurs before or after emergence, remains unclear. No critical morphological differences occur between potential queens of the next generation (often called gynes) and workers in primitively eusocial insects. The gynes of temperate species are characterized by diapausing, and the nutrients available during the larval stage have often been believed to determine caste fate. Short days usually induce diapause in temperate nonsocial insects, although few investigations of the effects of day length on caste-fate determination in paper wasps have been conducted. By exposing individuals to different combinations of short and long days during the immature and adult stages, we show for the first time that short days during the adult stage (but not during the immature stage) facilitated caste-fate determination toward gynes in a paper wasp. Moreover, the decision to diapause partly depended on changes in the photoperiod during the pupal and adult stages. The size of the adult also affected caste-fate determination, with diapause more likely to occur in large adults, but this size effect did not occur when individuals were exposed to many short days during the pupal stage. In addition, all adults except for a small proportion of smaller individuals prepared for diapause under short days. These findings suggest that the photoperiod is a higher priority cue than adult size.     

Development of a novel hybrid microwave-heater reactor for paper-based waste treatment

It is necessary to develop a medical waste management system featuring nonburning treatment and safety functions for small medical institutions. In this article, the development of a waste management system without oxygen injection was achieved by means of hybrid heating using microwave energy and an electric heater. The shape of the microwave reactor was a rectangular parallelepiped with a volume of about 0.1 m³. In the experimental setup, microwave energy (2.45 GHz, about 800 W) was injected from the top of the reactor, while the heater (about 1 kW) was located at the bottom. Heat insulators were set into all the walls of the reactor. The gases generated in the system were vented through water and activated carbon. Five paper-based diapers with absorbed water were used as the waste sample. For the evaluation of performance, the reduction rate was defined as the ratio (in percent) of the weight before and after treatment. The reduction rate as a function of treatment time and the effect of the position of the waste in the reactor on the reduction rate and the uniformity of treatment were examined for about 3 kg of waste. It was found that the reduction rate reached as low as 4.2% at 3 h and then 3% after 8 h. The treated profile strongly depended on the position of the waste in the reactor. In particular, it was clarified that a metal cylindrical enclosure and a needle electrode played an important role in attaining uniform treatment of the waste.     

Improvement of permeability of waste sludge by mixing with slag or construction and demolition waste

To determine the allowable ratio of waste sludge required to ensure an aerobic zone in the landfill, we investigated sludge permeability, which involved mixing sludge, the major landfill waste in Japan, at different mixing ratios with other wastes (slag and construction and demolition waste (C&D)). We measured parameters of sample permeability and analyzed parameters that exert a large influence on oxygen penetration depth with a simulation model accounting for both diffusion and convection driven by temperature gradients. We also determined the critical volumetric contents in which gas and/or water permeability change significantly when sludge is mixed with sand or gravel. From the results of the simulations, gas permeability of the layer, the difference between inside and outside temperatures and the oxygen consumption rate exert a large influence on the resulting oxygen penetration depth. The allowable ratio of sludge required to ensure an aerobic zone in the landfill was determined by considering the balance of the above three parameters. By keeping volumetric sludge content to below 25%, air convection and oxygen penetration depth of several meters were achieved in the modeling.     

The environmental photolysis of perfluorooctanesulfonate,perfluorooctanoate, and related fluorochemicals

A field study on the photolysis of perfluoroalkyl substances (PFASs) was conducted at high altitudes in Mt. Mauna Kea (Hawaii, USA; 4200 m) and Mt. Tateyama (Toyama, Japan; 2500 m). Results of photolysis of PFASs in the field were further confirmed in laboratory studies. Perfluorooctanesulfonate (PFOS), which is perceived as a non-degradable chemical in the environment, can undergo photolysis. Long chain PFASs can be successively dealkylated to short chain compounds such as perfluorobutyric acid (PFBA) and perfluorobutane sulfonate (PFBS), but the short chain compounds were relatively more resistant to photodegradation. These results suggest that environmental levels of short chain PFASs would increase both due to their formation from photolysis of long chain PFASs and from direct releases. Earlier studies on photolysis of PFASs were focused on the formation of perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) from precursor compounds (such as fluorotelomer alcohols) under laboratory conditions. Our study suggests that PFSAs and PFCAs themselves can undergo photodegradation in the environment.     

Effects of acute γ-irradiation on community structure of the aquatic microbial microcosm

To characterise indirect effects of ionising radiation on aquatic microbial communities, effects of acute γ-irradiation were investigated in a microcosm consisting of populations of green algae (Chlorella sp. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.) as producer; a ciliate protozoan (Cyclidium glaucoma), rotifers (Lecane sp. and Philodina sp.) and an oligochaete (Aeolosoma hemprichi) as consumer; and more than four species of bacteria as decomposers. Population changes in the constituent organisms were observed over 160 days after irradiation. Prokaryotic community structure was also examined by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA. Principle response curve analysis revealed that the populations of the microcosm as a whole were not significantly affected at 100 Gy while they were adversely affected at 500-5000 Gy in a dose-dependent manner. However, some effects on each population, including each bacterial population detected by DGGE, did not depend on radiation doses, and some populations in the irradiated microcosm were larger than those of the control. These unexpected results are regarded as indirect effects through interspecies interactions, and possible mechanisms are proposed originating from population changes in other organisms co-existing in the microcosm. For example, some indirect effects on consumers and decomposers likely arose from interspecies competition within each trophic level. It is also likely that prey-predator relationships between producers and consumers caused some indirect effects on producers.     

Elevated water temperature reduces the acute toxicity of the widely used herbicide diuron to a green alga, Pseudokirchneriella subcapitata

In the actual environment, temperatures fluctuate drastically through season or global warming and are thought to affects risk of pollutants for aquatic biota; however, there is no report about the effect of water temperature on toxicity of widely used herbicide diuron to fresh water microalgae. The present research investigated inhibitory effect of diuron on growth and photosynthetic activity of a green alga Pseudokirchneriella subcapitata at five different temperatures (10, 15, 20, 25, and 30 °C) for 144 h of exposure. As a result, effective diuron concentrations at which a 50 % decrease in algal growth occurred was increased with increasing water temperature ranging from 9.2 to 20.1 μg L^–1 for 72 h and 9.4–28.5 μg L^–1 for 144 h. The photochemical efficiency of photosystem II (F _v/F _m ratio) was significantly reduced at all temperatures by diuron exposure at 32 μg L^–1 after 72 h. Inhibition rates was significantly increased with decreased water temperature (P?<?0.01). Intracellular H₂O₂ levels as an indicator of oxidative stress were also decreased with increasing temperature in both control and diuron treatment groups and were about 2.5 times higher in diuron treatment groups than that of controls (P?<?0.01). Our results suggest water temperatures may affect the toxicokinetics of diuron in freshwater and should therefore be considered in environmental risk assessment.     

Effect of polyethylene addition to coal on hydrogasification enhancement

Hydrogasification of a coal/polyethylene mixture was carried out using a low concentration of polyethylene in the samples with the aim of industrial application. Coal/polyethylene mixtures in the ratio of 90:10 and 75:25 were used in this study. A hydrogasification experiment was conducted using a unique batch reactor at 1073 K under a 7.1 MPa hydrogen atmosphere. The reaction time varied from 1 to 80 s. The results revealed a methane yield from the mixtures that was noticeably greater than the values calculated from experimental results obtained from coal and polyethylene respectively, assuming no mutual influences. A significant synergistic effect was observed even when the polyethylene content was as low as 10 %. It is suggested that there might be an advantage in hydrogasification processes if waste plastics are mixed with coal, such content being practically assumed.