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BIOLOGICAL CONTROL OF UV ATTENUATION: NATURAL SUNSCREEN IN A CHANGING WORLDJordan, Kristen 01 August 2014 (has links)
Chromophoric Dissolved Organic Matter (CDOM) is a substance produced by the planktonic community that naturally blocks biologically damaging, ultraviolet radiation (UV; wavelengths = 280 to 400 nm). While a variety of planktonic species produce CDOM, investigations into the quality and quantity of their CDOM production are few. The purpose of this study was to investigate the properties of CDOM produced by phytoplankton versus zooplankton. Typically, UV radiation breaks down CDOM. However, marine organisms sometimes produce CDOM that, when exposed to sunlight, increases its absorbance of UV radiation. The reasons for this anomaly and the source of this unusual CDOM are unclear. To test for distinctions among sources, filtered water samples from cultures of two marine phytoplankton, Gymnodinium sp. and Dunaliella sp., and a marine copepod, Tigriopus californicus were exposed to sunlight for intervals of 0, 0.5, 1, 2, and 4 hours. The maximal UVB radiation (wavelengths; λ = 280 to 320 nm) was 0.1699 J cm-2. Before and after sunlight exposures, CDOM sources were assessed by comparing absorbance spectra from 184 to 730 nm with detailed comparisons at wavelengths of 254, 305, 320, and 350 nm. Results are expressed as "absorption", which is the raw absorbance converted to the natural log. Before exposure to sunlight, CDOM from algal species had 5- to 8-times higher average absorption values across UV wavelengths than CDOM produced by Tigriopus. CDOM samples produced by phytoplankton were more susceptible to photochemical change than CDOM from Tigriopus. In response to sunlight, CDOM from Gymnodinium varied greatly, increasing in UV absorption in 2 out of 5 replicates but decreasing in absorption in the other replicates. In contrast, peak absorption at λ = 260 nm of CDOM from Dunaliella decreased directionally by an average of 76% in absorption and 75% in specific absorption, and this decrease in absorption was significant (p = 0.03). CDOM from Tigriopus significantly decreased in both absorption (all UV wavelengths, p < 0.01) and "specific absorption", which is absorption standardized per mg of dissolved organic carbon (λ = 320 nm; p < 0.03), but the magnitude of change was only 17%. Thus, photochemical responses of CDOM from the three planktonic sources demonstrated more, consistently less, and unchanged UV absorption. Phytoplankton biomass, which is greater than that of copepods at the next trophic level, likely produce more CDOM but because of greater variability in CDOM absorbance of UV both within and between algal sources, copepods may offer a more stable source of UV protection depending on sunlight exposure and their relative abundance. Definitive conclusions depend on future laboratory studies expanded to more planktonic organisms as well as in situ studies during oceanographic cruises to test the relative contributions of planktonic species.
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DNA-Feulgen Cytophotometric Determination of Genome Size for the Freshwater-Invading Copepod Eurytemora AffinisRasch, Ellen M., Lee, Carol Eunmi, Wyngaard, Grace A. 01 June 2004 (has links)
Variation in nuclear DNA content within some eukaryotic species is well documented, but causes and consequences of such variation remain unclear. Here we report genome size of an estuarine and salt-marsh calanoid copepod, Eurytemora affinis, which has recently invaded inland freshwater habitats independently and repeatedly in North America, Europe, and Asia. Adults and embryos of E. affinis from the St. Lawrence River drainage were examined for somatic cell DNA content and the presence or absence of embryonic chromatin diminution, using Feulgen-DNA cytophotometry to determine a diploid or 2C genome size of 0.6-0.7 pg DNA/cell. The majority of somatic cell nuclei, however, have twice this DNA content (1.3 pg/nucleus) in all of the adults examined and possibly represent a population of cells arrested at the G2 stage of the cell cycle or associated with some degree of endopolyploidy. Both suggestions contradict assumptions that DNA replication does not occur in adult tissues during the determinate growth characteristic of copepods. Absence of germ cell nuclei with markedly elevated DNA values, commonly found for species of cyclopoid copepods that show chromatin diminution, indicates that E. affinis lacks this trait. The small genome size and presumed absence of chromatin diminution increase the potential utility of E. affinis as a model for genomic studies on mechanisms of adaptation during freshwater invasions.
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The postembryonic development of fish copepod (Caligoida, Lernaeoceriformes) in pelagic snails (Janthina spp.)Ho, Ju-Shey January 1965 (has links)
Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / In all, 7587 copepods were recovered from 115 pelagic snails of two species, Janthina janthina (Linnaeus) and J. globosa Swainson, which had been collected from the West Indies,and Madagascar. They were found either free inside the mantle cavities or fixed on to the gill lamellae of the snails, and represent a complete series of the postembryonic developmental stages of a lernaeoceriform copepod.
Five stages were recognized. They are:
1. Free-swimming copepodid: 0.42-0.48 mm.
The body has an oblong cephalothorax and four free segments.
There are two pairs of well-developed biramous legs. The third pair is represented merely by a pair of spines on the second free segment. The third free segment represents the fourth thoracic segment and carries no legs. The last free segment carries a pair of caudal rami which bear 4 plumose setae and one short setule. The first antenna is indistinctly 4-segmented, with the formula 1, 1, 1, and 11 plus one aesthete; the two long setae on the terminal segment are bifurcate. The second antenna is 3-segmented, chelate and powerful. The mouth tube is of the usual form found in lernaeoceriform copepods, There is, however, a pair of spatulate labial palps which have not been described before in any known lernaeoceriform copepodids. The mandible is lanceolate, without teeth. The first maxilla is bipartite: a small exopod armed with a single seta and a large endopod tipped with two stout setae. The second maxilla is 3-segmented, with a falciform terminal segment bearing striations. Each ramus of the first two pairs of legs is 1-segmented; the first exopod: III,I,3; the first endopod: 7; the second exopod: II,I,3; and the second endopod: 6 [TRUNCATED]. / 2999-01-01
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Chromatin Diminution in 'Mesocyclops edax' (Crustacea, Copepoda): Similarity of the Pre- and Post-diminution Euchromatic Genomes.McKinnon, Christian 18 October 2012 (has links)
Chromatin diminution is defined as the elimination of DNA during the differentiation of early embryonic cells into pre-somatic cells. While it was first observed in the nematode Parascaris equorum, it also been identified in other parasitic nematodes, hagfish and copepods. In the copepod Mesocyclops edax, up to 90% of genomic DNA is eliminated during chromatin diminution. It was previously shown that the eliminated DNA contained highly repetitive heterochromatic sequences. Here, we digested pre- and post-diminution DNA with BamHI and produced small libraries of clones from each. Analyses revealed no decrease in low copy numbered sequences, such as transposable elements. Rather, both libraries are found to be surprisingly similar in all aspects analysed. Further comparison also demonstrated similarity of our libraries with the DNA sequences eliminated from Cyclops kolensis. Consequently, we suggest that M. edax eliminates portions of euchromatic DNA, in addition to the previously characterized satellite sequences.
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Chromatin Diminution in 'Mesocyclops edax' (Crustacea, Copepoda): Similarity of the Pre- and Post-diminution Euchromatic Genomes.McKinnon, Christian 18 October 2012 (has links)
Chromatin diminution is defined as the elimination of DNA during the differentiation of early embryonic cells into pre-somatic cells. While it was first observed in the nematode Parascaris equorum, it also been identified in other parasitic nematodes, hagfish and copepods. In the copepod Mesocyclops edax, up to 90% of genomic DNA is eliminated during chromatin diminution. It was previously shown that the eliminated DNA contained highly repetitive heterochromatic sequences. Here, we digested pre- and post-diminution DNA with BamHI and produced small libraries of clones from each. Analyses revealed no decrease in low copy numbered sequences, such as transposable elements. Rather, both libraries are found to be surprisingly similar in all aspects analysed. Further comparison also demonstrated similarity of our libraries with the DNA sequences eliminated from Cyclops kolensis. Consequently, we suggest that M. edax eliminates portions of euchromatic DNA, in addition to the previously characterized satellite sequences.
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Analysis of interactive patterns between copepods and ciliates using indicators and data mining techniquesHsu, Chih-Yung 14 August 2008 (has links)
Even zooplankton can not be utilized directly by human being; it is an important food source for numerous economical fishes. Zooplankton¡¦s predator-prey interactions can affect not only global carbon fixation, but also fisheries yields directly. Copepods and ciliates are the targets of the current study, which act as critical links between classical diatom-copepod-fish webs and microbial food webs. Analyzing their predator-prey interactions can help us understand more about marine food production.
The objective of this study is to investigate the differences in swimming behavior of copepods and ciliates under two environments, which are disturbances and no disturbances of predator-prey. We use five locomotive indicators (NGDR, turning rate, diffusion coefficient, kinetic energy and fractal dimension) to quantify swimming patterns. The trajectories of copepods in the undisturbed situation show circuitous, larger turning angle, and more diffusive behavior, which associate with a lower kinetic energy. The patterns of copepod movement with the presence of prey (ciliates) are contrary to the previous situation. The patterns of ciliates in the undisturbed situation are similar to those of copepods in undisturbed situation, except smaller turning angles. The trajectories of ciliates in terms of the turning and diffusive movement when predators (copepods) show up are different from those of copepods when preys (ciliates) are present. In addition to indicators, this study develops a new encoding scheme for accommodating the spatial-temporal information embedded in the original data. By analyzing the encoded data through some data mining techniques, the predator-prey interactive behaviors in the spatial scale can be easily perceived.
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Factors affecting meiofaunal colonization and assemblage structure in marine soft sedimentsBoeckner, Matthew J. Unknown Date
No description available.
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Development of bioassay approaches to evaluate the impacts of pollution on New Zealand estuaries using the marine copepod Quinquelaophonte sp.Stringer, Tristan James January 2012 (has links)
Worldwide, estuaries are under increasing pressure from numerous contaminants. There is a need to develop reliable bioassay methodologies to assess the effects of these stressors on estuary health. This thesis aimed to develop and validate toxicity tests in a New Zealand marine harpacticoid copepod species for use in monitoring and evaluating the effects of estuarine pollution. A survey and toxicological assessment of a range of native copepod species resulted in the selection of Quinquelaophonte sp. as the ideal bioassay species. This selection was based on a broad regional distribution, ease of culture and high reproductive rate in the laboratory, sexual dimorphism, and sensitivity to contaminants. To validate the bioassay, spiked sediments were used to expose Quinquelaophonte sp. to three reference compounds representing important categories of estuarine chemical stressors: zinc (a metal), atrazine (a pesticide), and phenanthrene (a polyaromatic hydrocarbon). A method for spiking sediments that Quinquelaophonte sp. inhabit was developed to ensure even contaminant distribution in sediments. Two sediment bioassays using lethal and sublethal endpoints were validated, one acute (96 h) and one chronic (14 d). These assays incorporated both lethal and sublethal endpoints, which included reproductive output and mobility. Acute-to-chronic ratios were calculated for use in environmental risk assessment and to provide insight into the mode of action of the reference contaminants. The chronic sediment bioassay was used to assess sediment quality in three estuaries across New Zealand: Napier, Christchurch and Invercargill. This validated the bioassay for use with naturally-contaminated field sediments with varying mixtures of pollutants and sediment types (coarse sandy to fine silty organic rich sediments). Quinquelaophonte sp. was also tested to assess whether it can be used to characterise multi–generation impacts. After four generations of exposure to zinc, there were changes in acute sensitivity, indicating this species possesses mechanisms for acclimating or adapting to toxic stressors. Sediment bioassays in Quinquelaophonte sp. were successfully developed and validated, offering significant promise as a tool for monitoring effects of pollution in New Zealand estuaries.
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Factors affecting meiofaunal colonization and assemblage structure in marine soft sedimentsBoeckner, Matthew J. 11 1900 (has links)
Meiofauna are an abundant, diverse and important component of the marine
biota, however, much of their ecology has been neglected. Despite their high densities,
meiofaunal abundance is often patchy. Meiofauna present in high numbers at one site
will often be less abundant in seemingly similar adjacent sites. What factors govern this
variability? How readily do these animals colonize new patches? How do various
biological and environmental factors affect meiofaunal colonization rate and resulting
assemblage structure?
The response of meiofauna to changes in abiotic factors, including sediment grain
size, depth, exposure and distance from the ocean floor, was quite variable. Often one
factor would affect certain taxa and not others. Even slight increases in depth resulted in
drastic declines of harpacticoid copepods while nematodes were unaffected. Meiofauna
were also fewer in sediments with large interstitial spaces. Some meiofauna were most
abundant in sediments placed closer to the ocean floor. Other taxa colonized distant
substrata as rapidly as they did substrate located closer to the ocean floor. This suggested
differences between taxa in their rates of active dispersal.
The effects of macrofauna on meiofauna have been debated. In particular, how do
clams affect the colonization and assemblage structure of meiofauna? Certain
characteristics of clams were isolated and evaluated: feeding behaviour, bioturbation
rate/depth and metabolic byproducts. Clams that caused the greatest meiofauna declines
were shallow burrowing deposit-feeders. Constant disturbance to the upper sediment by
these clams was likely responsible for meiofaunal impact. Conversely, suspensionfeeding
clams that passed quickly to deeper sediment and remained stationary had little
impact on meiofauna.
Finally, a survey of local marine nematodes added nine genera new to Canada
and 24 genera new to British Columbia. A review was also compiled that shows
nematodes and other meiofauna have been neglected for much of Canada. Although
these small and abundant animals are quick to colonize even distant habitats they are
quite sensitive to cues from the surrounding biotic and abiotic environment. This
sensitivity combined with their ease of collection make meiofauna a valuable asset to any
number of ecological investigations. / Ecology
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Chromatin Diminution in 'Mesocyclops edax' (Crustacea, Copepoda): Similarity of the Pre- and Post-diminution Euchromatic Genomes.McKinnon, Christian January 2012 (has links)
Chromatin diminution is defined as the elimination of DNA during the differentiation of early embryonic cells into pre-somatic cells. While it was first observed in the nematode Parascaris equorum, it also been identified in other parasitic nematodes, hagfish and copepods. In the copepod Mesocyclops edax, up to 90% of genomic DNA is eliminated during chromatin diminution. It was previously shown that the eliminated DNA contained highly repetitive heterochromatic sequences. Here, we digested pre- and post-diminution DNA with BamHI and produced small libraries of clones from each. Analyses revealed no decrease in low copy numbered sequences, such as transposable elements. Rather, both libraries are found to be surprisingly similar in all aspects analysed. Further comparison also demonstrated similarity of our libraries with the DNA sequences eliminated from Cyclops kolensis. Consequently, we suggest that M. edax eliminates portions of euchromatic DNA, in addition to the previously characterized satellite sequences.
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