Three-dimensional reconstruction of the tissue-specific multielemental distribution within Ceriodaphnia dubia via multimodal registration using laser ablation ICP-mass spectrometry and X-ray spectroscopic techniques

In this work, the three-dimensional elemental, distribution profile within the freshwater crustacean Ceriodaphnia dubia was constructed at a spatial resolution down to S mu m via a data, fusion approach employing state-of-the-art laser ablation inductively coupled plasma-time-of-flight mass spectrometry (LAICP-TOFMS) and laboratory-based absorption microcomputed tomography (mu-CT). C. dubia was exposed to elevated Cu, Ni, and Zn concentrations, chemically fixed, dehydrated, stained, and embedded, prior to mu-CT analysis. Subsequently, the sample was cut into 5 pm thin sections that were subjected to LA-ICPTOFMS imaging. Multimodal image registration was performed to spatially align the 2D LA-ICP-TOFMS images relative to the Corresponding slices of the 3D mu-CT reconstruction. Mass channels corresponding to the isotopes of a single element were merged to improve the signal-to-noise ratios within the elemental images. In order to aid the visual interpretation of the data, LA-ICP-TOEMS data wete projected onto the mu-CT voxels representing tissue. Additionally, the image resolution and elemental sensitivity were compared to those obtained with synchrotron radiation based 3D confocal mu-X-ray fluorescence imaging upon a chemically fixed and air-dried C. dubia specimen

Responses of Hyalella azteca and Ceridaphnia dubia to reservoir sediments following Chelated Copper Herbicide Applications

In response to nuisance growths of algae and vascular plants, such as dioecious hydrilla ( Hydrilla verticillata L.f. Royle), copper formulations have been applied in lakes and reservoirs for a number of years. Concerns have arisen regarding the long-term consequences of copper applications and those concerns have appropriately focused on sediment residues. In this study, we evaluated the toxicity of sediments from treated (for a decade) and untreated areas in Lake Murray, South Carolina and estimated the capacity of those sediments to bind additional copper. Two sentinel aquatic invertebrates, Hyalella azteca Saussure and Ceriodaphnia dubia Richard, were used to measure residual toxicity of treated and untreated sediments from the field and after laboratory amendments. (PDF has 5 pages.

Seasonal abundance of small cladocerans in Lake Mangakaware, Waikato, New Zealand

The seasonal changes in the dynamics and life histories of the Cladocera in Lake Mangakaware, North Island, New Zealand, were studied over 19 months by sampling at weekly or 2-weekly intervals. Lake Mangakaware is a 13.3 ha polymictic lake with high nutrient status, low Secchi disc transparencies, and an unstable thermal regime. The four planktonic cladoceran species (Bosmina longirostris, B. meridionalis, Ceriodaphnia pulchella, and C. dubia) exhibited disjunct population maxima. Only B. longirostris was perennially present. All species exhibited low fecundities and low lipid content, indicating that food resources were limited and that competitive interactions and resistance to starvation were probably important in determining species success. Increases in body size in cooler seasons were unrelated to clutch size, giving further support for the view that available food was limited. These results are consistent with previous experimental findings that subtle differences in life history can determine seasonal success and the outcome of competition between similar species

Late Miocene Soricidae (Mammalia) fauna from Tardosbánya (Western Hungary)

The Soricidae (Mamrnalia, Insectivora) elements of the rich and well preserved fossil vertebrate fauna from Tardosbánya limestone quarry (Western Hungary, Gerecse Mountains) are presented. Five species could have been identified from the material: Amblycoptus oligodon KORMOS 1926, Crusafontina konnosi (BACHMAYER& WILSON, 1970), Blarinella dubia (BACHMAYER and WILSON, 1970), Episoricuius gibberodon (PETÉNYI, 1864) and Paenelimnoecus repenningi (BACHMAYER & WILSON, 1970). The occurrence of Crusafantina, B. dubia and P. repenningi indicates that the age of the sarnple is Late Miocene. The morphometrical studies on C. konnosi, and the morphology and the low relative frequency of A. oligodon suggest that the fauna is correlative with the Turolian MN 12 Zone. The occurrence of A. oligodon, C. konnosi and E. gibberodon indicates well watered, forested environment

Invasion of a littoral cladoceran Sida crystallina into the pelagic zone of Christine Lake, NH and its potential impact on the phytoplankton community

This study evaluated the phytoplankton community and grazing influences of the zooplankton in oligotrophic Christine Lake, NH, by assessing the body size and clearance rates of the three dominant crustaceans: Sida crystallina (0.08 individuals L-1 ), Daphnia dubia (0.11 individuals L-1 ), and Leptodiaptomus sicilis (2.11 individuals L-1 ). Sida crystallina, typically a littoral cladoceran, was abundant throughout the water column in the open water, and contributed approximately 44% of the grazing in the pelagic zone. Phytoplankton abundance was examined to assess the potential impact S. crystallina might have on the phytoplankton in Christine lake. Aphanocapsa, the dominant phytoplankton in Christine Lake (relative abundance 68.54%), is a picocyanobacterium capable of forming colonies in the presence of planktonic grazers. Its ability to out-compete other phytoplankton due to differential grazing pressure suggests the appearance of the strong grazer S. crystallina may have contributed to the dominance of cyanobacteria in this oligotrophic lake

Which morphological characteristics are most influenced by the host matrix in downy mildews? : A case study in Pseudoperonospora cubensis

Before the advent of molecular phylogenetics, species concepts in the downy mildews, an economically important group of obligate biotrophic oomycete pathogens, have mostly been based upon host range and morphology. While molecular phylogenetic studies have confirmed a narrow host range for many downy mildew species, others, like Pseudoperonospora cubensis affect even different genera. Although often morphological differences were found for new, phylogenetically distinct species, uncertainty prevails regarding their host ranges, especially regarding related plants that have been reported as downy mildew hosts, but were not included in the phylogenetic studies. In these cases, the basis for deciding if the divergence in some morphological characters can be deemed sufficient for designation as separate species is uncertain, as observed morphological divergence could be due to different host matrices colonised. The broad host range of P. cubensis (ca. 60 host species) renders this pathogen an ideal model organism for the investigation of morphological variations in relation to the host matrix and to evaluate which characteristics are best indicators for conspecificity or distinctiveness. On the basis of twelve morphological characterisitcs and a set of twelve cucurbits from five different Cucurbitaceae tribes, including the two species, Cyclanthera pedata and Thladiantha dubia, hitherto not reported as hosts of P. cubensis, a significant influence of the host matrix on pathogen morphology was found. Given the high intraspecific variation of some characteristics, also their plasticity has to be taken into account. The implications for morphological species determination and the confidence limits of morphological characteristics are discussed. For species delimitations in Pseudoperonospora it is shown that the ratio of the height of the first ramification to the sporangiophore length, ratio of the longer to the shorter ultimate branchlet, and especially the length and width of sporangia, as well as, with some reservations, their ratio, are the most suitable characteristics for species delimitation

Are zooplankton invasions in constructed waters facilitated by simple communities?

The invasion of non-indigenous species is considered to be one of the leading causes of biodiversity loss globally. My research aimed to determine if constructed water bodies (e.g., water supply reservoirs, dams and ponds) were invaded by zooplankton with greater ease than natural water bodies, and whether this was due to a lower biodiversity, and therefore lower 'biotic resistance', in constructed water bodies. Sediment cores were collected from a cross-section of 46 lakes, ponds and reservoirs (23 natural and 23 constructed) throughout the North Island, New Zealand. Diapausing zooplankton eggs were separated from the sediments and hatched to assess species composition and richness. In addition, the distributions of non-indigenous zooplankton were examined to determine if they occurred more frequently in constructed water bodies than in natural ones. Species composition results showed that natural water body zooplankton communities appeared to consist mainly of a core group of truly planktonic species. However, the species assemblages of constructed water bodies were more varied, comprising of a number of littoral and benthic species, and a large number of species that were recorded from only a single water body. A canonical correspondence analysis indicated that Trophic Level Index explained a significant amount of variation in zooplankton community composition of natural waters (p = 0.002). Distance to nearest water body and number of water bodies within a 20 km radius explained significant amounts of variation in community composition of constructed water bodies (p = 0.040 and 0.038 respectively). Average species richness was slightly higher for natural water bodies than constructed water bodies (18.47 and 15.05 respectively), although overall there was a lot of variation for both natural and constructed water body datasets. A stepwise linear regression indicated that latitude and approximate maximum depth of water body were significant predictors of natural water body species richness (p = 0.002 and 0.016 respectively). However, no significant predictors of species richness were elucidated for constructed water bodies. The non-indigenous calanoid copepods Sinodiaptomus valkanovi and Boeckella minuta were only found in constructed water bodies. However, the non-indigenous cladoceran Daphnia galeata was recorded in both natural and constructed water bodies. The non-indigenous calanoid copepods are more likely to establish populations in constructed water bodies due to the absence of key species (i.e. native calanoid copepods), whose presence in natural waters seemingly provides 'biotic resistance'. The invasion success of D. galeata in constructed and natural waters may be attributed to the absence of a superior competitor, as native Daphnia populations, for example, are rare in the North Island. My results suggest that species richness may not be as important as species composition in influencing the ease with which non-indigenous species invade constructed water bodies. The core group of species found in natural water bodies are likely to be better adapted to pelagic conditions, and therefore better at resisting invaders, than the more varied constructed water body assemblages

TOXICITY OF PREDNISOLONE, DEXAMETHASONE AND THEIR PHOTOCHEMICAL DERIVATIVES ON AQUATIC ORGANISMS

Light exposure of aqueous suspensions of prednisolone and dexamethasone causes their partial phototransformation. The photoproducts, isolated by chromatographic techniques, have been identified by spectroscopic means. Prednisolone, dexamethasone and their photoproducts have been tested to evaluate their acute and chronic toxic effects on some freshwater chain organisms. The rotifer Brachionus calyciflorus and the crustaceans Thamnocephalus platyurus and Daphnia magna were chosen to perform acute toxicity tests, while the alga Pseudokircheneriella subcapitata (formerly known as Selenastrum capricornutum) and the crustacean Ceriodaphnia dubia to perform chronic tests. The photochemical derivatives are more toxic than the parent compounds. Generally low acute toxicity was found. Chronic exposure to this class of pharmaceuticals caused inhibition of growth population on the freshwater crustacean C. dubia while the alga P. subcapitata seems to be less affected by the presence of these drugs

Three new and remarkable species of mosses from China and the Philippines

Distichophyllum meizhii Tan & Lin and D. wanianum Tan & Lin (Hookeriaceae) collected from southwestern region of China are described as new to science. Also, Horikawaea redfearnii Tan & Lin is described as a new species based on collections from Hainan Island of China and Palawan Island of the Philippines. The sporophytic specimen of Horikawaea Nog. was collected for the first time and support a family placement in Pterobryaceae