Host preference of a symbiotic flatworm in relation to the ecology of littoral snails

Some polyclads associate with other marine invertebrates such as gastropods, but how these associations evolve is not well understood. This study examined the relationships between a polyclad, Stylochoplana pusilla, and six species of snails in 10 eulittoral sites in Mutsu Bay, northern Japan, in 2010 and 2011. Of the six potential host snail species, Monodonta labio was present at all sites and the prevalence of S. pusilla in the snails’ mantle cavities overall was 82.6 %. Four other snail species occurred at five or six sites in comparable densities, but of these, only Chlorostoma turbinatum and Omphalius rusticus had S. pusilla in their mantle cavities (prevalence of 42.0 and 15.4 %). A congener of M. labio, Monodonta neritoides, occurred at only one site and had no S. pusilla. The mantle, which provides habitat space for S. pusilla, was proportionally the longest in M. labio. In laboratory experiments, the flatworms preferentially entered M. labio over other snail species with the same mantle length. Observed vertical distributions of snails in the littoral zone indicate that M. labio is present in the eulittoral at both high and low tides, while C. turbinatum and O. rusticus are usually found in the sublittoral. In an evolutionary sense, the relationship between S. pusilla and its host may have developed as a mechanism for the flatworm to avoid predation by living in the eulittoral and to avoid desiccation by establishing commensal relationships with certain snails.     

Gas-particle partitioning of PCDD/Fs in Nagoya urban air, Japan

Polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) in the atmosphere were sampled by a high-volume filter/sorbent air sampler at an urban (Nagoya, Japan) site from May 2000 to January 2001 under the average ambient temperatures ranging from 1 degrees C to 33 degrees C. The gas and particle phase concentrations of PCDD/Fs were measured and then the field gas-particle partitioning data were used to assess the Junge-Pankow adsorption model and the K(OA) absorption model. For both PCDDs and PCDFs, passable agreement was obtained between the measured and predicted particulate-band fraction (phi) values by the Junge-Pankow model, but the model tends to overpredict phi for all individual Cl4-8DD/F congeners, especially for the lower chlorinated congeners. On the other hand, good agreement was obtained between the measured and predicted log K(p) values by the K(OA) model for both PCDDs and PCDFs. However, the K(OA) absorption model did not fit the field data at low ambient temperature below 5 degrees C. The disagreement at low ambient temperatures was estimated to arise from the gas adsorption artifacts during the sampling. From the validation by the field measurement data in Nagoya urban air, it is found that the K(OA) absorption model is capable of predicting more accurately gas-particle partitioning of PCDD/Fs than the Junge-Pankow adsorption model.     

Photodegradation of pentachlorophenol and its degradation pathways predicted using density functional theory

The objectives of the present research were (i) to report the mass balance of chlorine during pentachlorophenol (PCP) photodegradation and (ii) to reveal the photodegradation pathway experimentally with a theoretical proof based on the density functional theory (DFT). The chlorine of PCP was completely mineralized to produce chloride ions after 24h of UV irradiation. As intermediates, 2,3,5,6-tetrachlorophenol, 2,3,4,6-tetrachlorophenol and 2,5-dichlorophenol were identified. At least 80% of the chlorine balance during PCP photodegradation was accounted by PCP, these intermediates, and chloride ions. A DFT calculation showed differences in the C-Cl bond dissociation energy level and the positions of respective PCP molecular and the PCP intermediates. The dechlorination intermediates predicted using the calculated C-Cl bond dissociation energy were consistent with those experimentally confirmed, indicating the feasibility of this theoretical method in predicting the dechlorination pathway.     

Analyses on phenological and morphological variations of mangrove forests along the southwest coast of Bangladesh

Drastic changes in river discharge and salinity levels are threatening the phenology and morphology of the coastal mangrove forests of the Sundarbans of Bangladesh. We have used AVHRR GIMMS (1985–2006) and MODIS (2005–2010) satellite Normalized Difference Vegetation Index (NDVI) data to identify the temporal variation of the phenology of the mangroves. Linear interpolation and Fourier-based adjustment were applied to remove noise from the NDVI time series. Then linear regression analysis on a single area (8 km ? 8 km) and a composite of 36 areas for three NDVI statistics the annual minimum, annual average, and annual maximum were performed--over the time periods 1985–1990, 1990–2000, 2000–2006 and 2005–2010 to identify possible functional changes in NDVI time series around the Sundarbans. Furthermore, we used fourteen LANDSAT images spanning the period 1989–2010 to estimate the spatiotemporal rate of shoreline changes over the three time periods 1989–2000, 2000–2006, and 2006–2010. A decreasing trend in the annual minimum NDVI was observed in most of the areas of the Sundarbans for the period 1990–2000. During the years 2000–2006, the trends of the three NDVI statistics became significantly positive, indicating an improvement of the mangrove phenology. In the period 2005–2010, a decreasing trend in all the NDVI variables was again dominant. The coast underwent rapid erosion from 1989–2000 and 2006–2010. However, the rate substantially declined between 2000 and 2006, when accretion was dominant. The advent of the upstream Farakka barrage caused a significant reduction in the Ganges-Gorai River discharge and increased the salinity in and around the Sundarbans. Our study concludes that this may be responsible for the degradation of mangrove phenology and accelerated erosion in the earlier and recent periods. In the interim, 2000–2006, improved river discharge and salinity levels due to the Ganges water sharing agreement (1996) and dredging of the Gorai River bed (1998–1999) enhanced the mangrove phenology and helped the coast to gain land.     

Sorption of alkylphenols on Ebro River sediments: comparing isotherms with field observations in river water and sediments

This study reports sorption isotherms of the endocrine disruptors nonylphenol (NP) and octylphenol (OP) in three sediment samples from the Ebro River basin (NE Spain), with organic carbon fractions (f_OC) ranging from 0.0035 to 0.082 g_OC g⁻¹. All isotherms were fitted to the Freundlich model with slightly nonlinear exponents ranging from 0.80 to 0.94. The solubility of the compounds as well as the organic carbon (OC) content had the strongest influences on the sorption behavior of these compounds. Comparison of the laboratory-spiked samples with the native contamination of NP of 45 water and concurrent sediment samples resulted in reasonable matches between both data sets, even though the lowest concentrations in the field were not completely reached in laboratory tests. This good agreement indicates that sorption laboratory data can be extrapolated to environmental levels and therefore the distribution of nonylphenol between sediments and water can be predicted with a precision of one order of magnitude. Furthermore, laboratory experiments with simultaneous loading of NP and OP revealed negligible competition for sorption sites at low concentrations.     

Spectroscopic analysis of NIR-dye sensitization in bulk heterojunction polymer solar cells

The photovoltaic conversion efficiency for near-infrared (NIR) sunlight is improved successfully by dye sensitization of bulk heterojunction polymer solar cells, in which the active layer was prepared by a ternary blend of poly(3-hexylthiophene), a fullerene derivative (1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene), and an NIR dye, silicon phthalocyanine bis(trihexylsilyl oxide). The mechanism of the NIR-dye sensitization is studied by femtosecond transient absorption spectroscopy.     

Spectroscopic Analysis of NIR-Dye Sensitization in Bulk Heterojunction Polymer Solar Cells

The photovoltaic conversion efficiency for near-infrared (NIR) sunlight is improved successfully by dye sensitization of bulk heterojunction polymer solar cells, in which the active layer was prepared by a ternary blend of poly(3-hexylthiophene), a fullerene derivative (1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene), and an NIR dye, silicon phthalocyanine bis(trihexylsilyl oxide). The mechanism of the NIR-dye sensitization is studied by femtosecond transient absorption spectroscopy.     

Correlation of low-volatile organic chlorine (LVOCl) and PCDD/Fs in various municipal waste incinerators (MWIs)

Medium- and low-volatile organic chlorine (M/LVOCl) and PCDD/Fs in flue gas from various municipal waste incinerators (MWIs) were monitored. The sample for M/LVOCl was collected in an adsorption tube which was thermally desorbed and the amount of chlorine was measured by atomic emission spectrometry (AES) detection using radiofrequency helium plasma. The helium plasma excited chlorine having an optical emission line of 837.6 nm was monitored. The MVOCl and LVOCl were organic chlorine groups whose boiling points (bp) ranged from 70-120 degrees C and 170-270 degrees C, respectively. The compounds having bp 120-170 degrees C were distributed in two tubes. LVOCl correlated well with PCDD/Fs (ng/Nm3, r=0.81) in a wide range of 0.01-100 ng/Nm3 of PCDD/Fs, while the correlation of LVOCl vs. TEQ was less related (r=0.69). These results agreed with the fact that LVOCl monitored the amount of organic chlorine without molecular structure information, which is critical to toxicity. Since the bp of LVOCl was not identical with that of PCDD/Fs, the regression was effected by the conditions of the gas treatment devices. Because most data of 2001 were collected just after the installation of PCDD/Fs in MWIs, the regression of 2001 was slightly different from that of 2002-2003. Eliminating these initial unsteady data, the regression of LVOCl vs. PCDD/Fs became better, giving r= 0.86. Besides having PCDD/Fs as surrogates, M/LVOCl is valuable as a versatile element-selective organic chlorine monitor to improve thermal process control.     

Perceived predation risk and mate defense jointly alter the outcome of territorial fights

Virtually all animal conflicts occur over access to mates or resources that affect survival, the two key components of fitness. In this paper, we report that predation risk and mate defense jointly affect the outcomes of contests between male sand crabs (Scopimera globosa) for burrows in which crabs mate and take shelter from predators. We observed the contests under three different conditions: (1) the natural condition of low predation risk and without the presence of a female; (2) the first experiment in which we imposed upon only intruding males the perception of predation risk—by digging them from their burrows, capturing and handling them, and placing them into other males’ burrows—to increase the value of the burrows for the intruders as shelter, and (3) the second experiment in which we repeated this treatment but increased the resource value of the burrow to the resident by placing a female in his burrow. The difference in body size between contestants was the main determinant of victory in all analyses. However, perceived predation risk also partly affected the outcomes of the fights: The motivated intruders were likely to win even when they were a little smaller than the residents. In addition, defense of a female had a significant effect on the outcomes of fights: The motivated residents won more fights than the motivated intruders, indicating that these two treatments caused asymmetric increases of the resource value. This is the first report of two external factors simultaneously raising resource value, affecting motivation of contestants, and altering the outcome of fights.