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Two methods of collection were employed in the investigation of the density, distribution, and movements of invertebrates inhabiting the Chara zone of lakes: (1) Chara samples were obtained at regular depth intervals over the Chara shoals with the aid of Scuba gear, partitioning the Chara stand into two approximately equal vertical halves - top half and bottom half; (2) a long-handled dipnet was used to sample the surface of the Chara stand and the waters above the stand. Sampling with the dipnet on a 24-hour basis provided data on the diel movements of organisms in the Chara zone. The density of the invertebrate populations was lowest in June due to the reduction of stocks over the winter months by predation and other causes of death. The high numbers in September were attributed to the results of early summer reproduction. Fluctuations in density over the summer months were traced to the changing interplay between hatching and emergence of various invertebrate groups. Eradication of fish from one of the lakes resulted in an increase in numbers of the major fish-food organisms, indicating predation by fish as an important factor controlling density of invertebrate stocks. The distribution of invertebrate organisms over the Chara shoal from shore to the limit of the vegetation offshore and vertically within the Chara bed itself was remarkably homogeneous. Minor differences in distribution of several invertebrate groups were demonstrated by statistical means. Daily vertical and horizontal movements of many of the organisms were shown to produce large density fluctuations on the Chara surface. / Science, Faculty of / Zoology, Department of / Graduate

A study of the secondary metabolism of two northeastern Pacific sponges and two Sri Lankan nudibranchs has led to the isolation of thirteen new and one previously known natural products. The structures of all of the compounds were determined by a combination of spectroscopic data analysis and chemical interconversions. A study of the chemistry of the northeastern Pacific sponge Hexadella sp. has resulted in the isolation of six new brominated alkaloids. Two of these, hexadellins A (77) and B (78), are derived from dibromotyrosine. The structures of compounds 77 and 78 were determined via their acetylated derivatives 79 and 80. Four compounds possessing novel bis(indole) structures have also been isolated. Topsentin B2 (74) was isolated as a mixture of two slowly interconverting tautomers, 74a and 74b. Methylation of 74 resulted in the production of trimethyltopsentin B2 (75); the structure of 75 was determined spectroscopically. The structures of dragmacidons A (81), B (82), and C (83) were determined by a combination of spectral data interpretation and chemical interconversions. Dragmacidon C (83) was originally incorrectly assigned as 88; the correct structure was determined based upon synthesis of the model compound 94. Compounds 77 and 78 possess antimicrobial activities. Compounds 74 and 81 show considerable cytotoxic and antineoplastic activities. Five new triterpene glycosides have been isolated from the northeastern Pacific sponge Xestospongia vanilla. The structures of isoxestovanin A (125), xestovanin C (127), dehydroxestovanin A (129), epi-dehydroxestovanin A (131), and dehydroxestovanin C (132) were all determined by a combination of spectral data interpretation and chemical interconversions. These compounds all contain the deoxy sugars L-rhamnose and D-fucose. Isoxestovanin A (125) possesses a new carbon skeleton and xestovanin C (127) and dehydroxestovanin C (132) possess linear trisaccharide fragments which have not been previously encountered in triterpene glycosides isolated from X. vanilla. The Sri Lankan nudibranch Chromodoris glenei has yielded the known compound 12-desacetoxyshahamin C (153) and the new metabolite shahamin K (155). Both compounds possess dendrillane diterpene skeletons. The compound chromodorolide B (156) was isolated from specimens of Chromodoris cavae. It is only the second known diterpene natural product possessing the chromodorane skeleton. / Science, Faculty of / Chemistry, Department of / Graduate

Squoxin, 1,1'-methylenedi-2-naphthol, is a pesticide developed to eradicate the northern squawfish, Ptychocheilus oregonensis. Investigations concerning the acute toxicity of the pesticide to aquatic invertebrates and an assessment of its fate in aquatic ecosystems are reported. Squoxin was found to be much less toxic to aquatic invertebrates than it was to squawfish. It was proposed that the toxicity of squoxin to aquatic invertebrates is inversely proportional to their adaptations to habitats having low levels of oxygen availability. The most sensitive invertebrate species tested was the blackfly larva, Simulium canadense, which is distributed in streams having high current velocity and abundant dissolved oxygen. These larvae exhibit an LC50 value of 60 ug/l in 48 hours. Chaoborus trivittatus larvae, known to tolerate anoxic conditions, were resistant to treatments up to 10 mg/1, exhibiting a maximum response of 30 percent in 96 hours. The degradation of Squoxin was monitored in surface waters of diverse origin. Degradation was most severe in water having a high pH and high alkalinity. Degradation was also found to occur due to the presence of dissolved organic compounds of high molecular weight. Freshwater bacteria did not exhibit any ability to utilize Squoxin as a carbon source in short term tests. A 100 ug/l Squoxin treatment depressed the natural heterotrophic activity of bacteria by nearly 25 percent based on studies of uptake of ¹⁴C-glucose over a 2 hour period. ¹⁴C-Squoxm residues initially adsorbed to phyto-plankton and organic sediment in simple laboratory microcosms. However, the residues steadily desorbed from these components and became increasingly soluble throughout the test period. Daphnia pulex and Hyalella azetca in the microcosms took up Squoxin rapidly in the first 24 hours after treatment. Uptake then levelled off and tissue concentration of Squoxin increased only at a very slow rate during the remainder of the test. Only small amounts of Squoxin were transferred to organisms feeding on contaminated food items when compared to the dose obtained from a contact exposure. C. trivittatus fed contaminated D. pulex retained only 6 percent of the ingested Squoxin residues. These residues, however, appeared to be retained for a longer period than tissue residues gained through a contact exposure. Invertebrates exhibited an ability to excrete Squoxin residues given time and an uncontaminated environment. D. pulex excreted over 90 percent of the toxicant in 96 hours; H. azteca required 275 hours. It was postulated that because of Squoxin's water solubility, low partition coefficient, rapid degradation, and the ability of a wide variety of organisms to excrete it, the toxicant would not be biologically magnified to a significant degree in aquatic ecosystems. / Science, Faculty of / Zoology, Department of / Graduate

This study was an attempt to evaluate the effects on ten Rocky Mountain streams from management activities on U.S. Forest Service lands. Macroinvertebrate and water chemistry data were collected. Data analysis methods included: three diversity indices, a numerical taxonomy system of multivariate statistical analysis, numbers and biomass per selected taxa, percent composition per order, and total numbers and biomass. None of the methods of analysis were found to be adequate if used alone, but by using a combination of dendograms, biomass, and numbers data in addition to the diversity indices (SCI and d) stream stress could be detected. Although organic water pollution generally did not reach levels of concern, other forms of stress, such as siltation and altered flows, became evident upon data analysis. In general, stream insect communities studied showed quick recovery from short-term stresses but definite negative responses to chronic stresses.

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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed on Feb. 6, 2007). PDF text: xii, 196 p. : ill., maps. UMI publication number: AAT 3220344. Includes bibliographical references. Also available in microfilm and microfiche format.