Nutritional aspects of three species of marine fish larvae, herring Clupea harengus L., plaice Pleuronectes platessa L. and turbot, Scophthalmus maximus L. were examined. Larvae were fed three different diets all of which were derived from rotifers Brachionus plicatilis (O.F. Mtlller). These rotifers had been mass cultivated on baker's yeast and then enriched with baker's yeast, or with one of two unicellular algae, Isochrysis galbana Park or Nannochloropsis (Nannochloris) oculata (Droop) Hibberd. The biochemical changes that these enrichments conferred on the rotifer were examined. There was little difference in proximate and amino acid compositions. Dry weights, and calorific contents of the rotifers fluctuated according to the type, temperature and duration of enrichment, with the yeast enriched rotifers tending to weigh less (200-320 ng) than their algal counterparts (250-370ng). Major differences were found in the total fatty acid profiles of the rotifers. Yeast-enriched rotifers had no 18:3n-3 or 20:5n-3 and only trace amounts of 22:6n-3 fatty acids. The Nanrinochioropsis-enriched rotifers had substantial amounts of n-3 fatty acids though only of 20:5n-3 (11-14%), while rotifers enriched with Isochrysis had only trace amounts of 20:5n-3 (2-4%). All three species of fish responded similarly to the yeast enriched rotifer diet. Their growth, in terms of length and weight, was minimal and they never developed any fin ray elements. Both flatfishes developed a looped gut in the short growth duration on this diet and some turbot (20%) inflated their swim bladder. This retardation of growth was attributed to the lack of long chain highly unsaturated n-3 fatty acids (n-3 HUFA) in the diet. During one month feeding trials it was shown that herring and plaice were able to exploit both algal-enriched rotifer diets equally well. Turbot, on the other hand grew better, over 14 days, on rotifers enriched with lsochrysis compared with Nannochioropsis. The reaction of the different species was linked to the fatty acid profiles of the diet. Hence, turbot require a dietary input of 22:6n-3 while herring and plaice thrived equally well on diets containing only 20:n-3. Juvenile plaice consistently exhibited improved pigmentation when Isochrysis compared to Nannochloropsis were used as the rotifer enrichment. The effect was attributed to specific nutrients particular to algal chloroplasts, which need to be present in the diet of the larvae up to metamorphosis. Assessment of daily rations, employing the rotifer enriched with Isochrysis diet only, showed herring to reduce their food intake from 46 to 19% body dry weight/d between days 10-21 post hatch while turbot consumed between 34-169% body dry weight/d with no apparent age related effects. The gross growth efficiencies (Ki, Brett & Groves, 1979) for both species were seemingly unaffected by age related processes and fluctuated between 15-50% in turbot and 20-61% in herring according to fluctuations in daily food intake. Ingestion is further described for both species with a linear model that related food intake to larval weight. The weight-specific ingestion was found to be a constant 13% and 43% of body dry weight in herring and turbot respectively. The weight-specific ingestion and specific growth rate estimates were combined with other data available from the literature, revealing that larvae tend to consume food (in dry weight) at a level equivalent to approximately twice their daily dry weight increase.

Abstract The objective of this thesis is to study the biological effects of larvae of Aedes albopictus induced by ultrasound exposure. Ultrasound is widely used in medical and biological techniques, most of them are cell killing or tumor eliminating by high-intensity ultrasound. In order to analyse the influences of ultrasound biological effects in vivo, the larvae of mosquito, in this research, were exposed to continuous-wave ultrasound. Some preliminary observations were made with 0-day larvae. The oscillation of the trachea in larvae in response to the ultrasound radiation is simulated using Miller¡¦s cylindrical-bubble activation theory. Dimensions of tubes in the respiratory system of larvae were measured by microscope. The resonant frequency of the tracheae were calculated, and its range is about 0.6¡ã1.5 MHz. It was observed that the tracheae in 0-day larvae were ruptured by ultrasound exposure, and the larvae were dead in the duration of growth, some fourth instar larvae failed to mature into pupae. The maximum mosquito larvae mortality was with 1 MHz irradiation, and it¡¦s in good agreement with the resonant frequency calculated in this paper.

No description available.

Addiction to alcohol is a disease of changed behavior that is uniquely human in it's complexity. Because of this, researchers have strived to develop animal models of individual endophenotypes of alcoholism in hopes that the larger picture will eventually come into focus. Recent studies in Drosophila have shown that many complex alcohol-related behaviors are conserved in this genetic model system. The series of projects presented in this dissertation outline the first account of physiological ethanol dependence in Drosophila. We first show that Drosophila larvae are able to form conditioned associations between an aversive heat stimulus and an attractive odor. We then show that an acute, low-dose ethanol exposure disrupts this learning ability. Finally, we present data that demonstrate that larvae adapt to the presence of chronic ethanol to the point that they only perform normally in the learning assay when ethanol is present in the animal. We then propose that the major mechanism for this dependence involves ethanol regulating the acetylation level and therefore expression level of a large number of genes by inhibiting histone deacetylase enzymes. These experiments set the groundwork for the analysis of a network of genes, connected through interactions with histone deacetylase enzymes, that are involved in producing ethanol dependence. / text

Silver nanoparticles (AgNPs) have gained much popularity in consumer products due to their strong antimicrobial ability. The majority of research concerning the biological effects of AgNPs has been limited to humans, mammals and freshwater organisms. Marine organisms, especially invertebrates, have been studied to a lesser extent. The objective of this thesis was to understand the effects of AgNPs on the marine benthic invertebrates. Specifically, we focused on the acute and sub-lethal toxicity of two AgNPs (Oleic acid coated AgNP (OAgNP) and Polyvinylpyrrolidone coated AgNP (PAgNP)) on marine invertebrate larvae across three phyla (i.e. the barnacle Balanus amphitrite, the limpet Crepidula onyx and the polychaete Hydroides elegans) in terms of mortality, growth, development and metamorphosis. Bioaccumulation and biodistribution of silver, as well as apoptosis induction were also investigated. To distinguish the toxic effects derived from nano-silver and aqueous form of silver, larvae were also exposed to silver nitrate (SN) in parallel. In the acute toxicity test, larvae were exposed to OAgNPs and PAgNPs for 48 hours, and the concentration leading to 10 % mortality (〖LC〗_10) were determined and compared. The results indicated that B. amphitrite and H. elegans were more sensitive to OAgNPs (〖LC〗_10: 0.138 and 2.63 × 〖10〗^(-4) μμg L-1, respectively) than PAgNPs (〖LC〗_10: 0.502 and 0.317 μμg L^(-1), respectively). In contrast, C. onyx was more susceptible to PAgNPs (LC10: 38.5 μμg L^(-1)) than OAgNPs (〖LC〗_10: 467 μμg L^(-1)). Among the three taxonomic groups, C. onyx was most tolerant of AgNPs, following by B. amphitrite and H. elegans. The sub-lethal effect of AgNPs resulted in a significant retardation in growth and development, and the reduction of settlement rate of all three species tested. In particular, the settlement rate of H. elegans was significantly lower in AgNPs treatment than in SN treatment, suggesting that toxicity of AgNPs might not be solely evoked by the release of silver ion (Ag+) into the test solution. The three species took up and accumulated silver efficiently from all forms. Importantly, AgNP aggregates were found along the digestive tract of C. onyx and the TEM images further confirmed that AgNPs were able to move across the plasma membrane. In addition, TUNEL assay indicated that AgNPs could induce apoptosis in B. amphitrite and C. onyx. In view of the very low number of detected apoptotic cells and the random occurrence of cell death found, AgNP-induced apoptosis does not appear to be the major toxicity mechanism in causing delayed growth and settlement failure. Unlike the results revealed from acute toxicity test, surface coatings did not affect the sub-lethal toxicity of AgNPs. This research clearly demonstrated that AgNPs exerted toxic effects in a speciesspecific manner, and long-term exposure of AgNPs might allow bioaccumulation of silver, induce apoptosis, and affect growth, development and recruitment of marine invertebrates. This study also highlighted the possibility that toxicity of AgNPs might be mediated through toxic Ag+ as well as the novel modalities of AgNPs. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

No description available.

Populations (n = 25) of fourth instar Aedes aegypti were introduced into observation arenas that contained one of 5 types of substrates, and were sub-divided into 5 equal 1 cm horizontal zones. The larvae were videotaped to determine effects of food quality, food quantity, and nutrient deprivation on vertical distribution of larvae over time. At least two-thirds of the larvae consistently aggregated at the surface and on the bottom. The proportion depended on the nature of the substratum and was influenced by nutrient deprivation. In contrast, density of larvae in the 3 remaining zones was consistently low and was unaffected by either of these variables. Larvae were typically very active during a 15 minute period of acclimation upon introduction into the observation arena; subsequently, levels of activity declined. Most starved larvae in the presence of a high-quality food substrate fed to repletion faster than fed larvae, whereas in an arena devoid of food, they foraged on the bottom for a longer duration of time than the fed. With a substrate of a semi- or highly non-nutritive nature, foraging again appeared more intense among starved than fed individuals. Starved larvae consistently aggregated on the bottom, in contrast to fed individuals that became more evenly distributed between the surface and the bottom.

The thyroid hormone system plays a major role in larval development, growth, and metabolism in fish. Therefore, any anthropogenic alteration in thyroid function could have dramatic effects on individual fitness. In this study Lake Sturgeon, Acipenser fulvescens, larvae were exposed to a commercially used organophosphate pesticide, chlorpyrifos (0, 5, 500 and 2000ng/L), from hatch until the onset of exogenous feeding (~12 days at 14C). The presence of thyroid follicles was first observed at 6 days post hatch (dph). Molecular expression of thyroid receptor α (TRα) increased from 3 to 12dph and then decreased from 12 to 21dph. TRα expression was also significantly higher in brain, liver and muscle at 67dph when compared to TRβ. Of the circulating hormones only free-T3 was consistently measured in larval homogenates from all development time-points sampled. Exposure to chlorpyrifos had no effect on growth or thyroid follicle morphology during the course of the experiment.

The fungus Ascosphaera apis causes the disease chalk brood in larvae of the honey bee, Apis mellifera. Ascospores were recognised as the agents of disease, but the site of their germination to initiate infection had not been established. In this study larval surface cuticle was initially investigated as a possible site, but spores did not even activate here. Therefore, potential inhibitors of spore germination were studied, including water and chloroform washings of larval cuticle; 4 larval food constituents - pollen, honey, brood food, royal jelly; and a variety of medium-chain fatty acids a t concentrations of 1, 0.1 and 0. 01%. Royal jelly exhibited a severe inhibitory effect on all germination stages. Larvae were successfully infected by feeding them food Containing A. apis spores, both in vitro and in vivo. A histological study of infected larvae demonstrated germination of spores in the mid-gut lumen, followed by penetration of the peritrophic membrane and gut epithelium by developing hyphae; and subsequent invasion of larval tissues by mycelia. Various aspects of spore physiology were investigated. Spore activation and enlargement were shown to be independent of temperature within the ranges of 10 to 40°C and 25 to 40°C respectively, while germ-tube production was closely temperature related, only occurring between 25 and 37°C - with an optimum between 31 and 35°C . However, all 3 germination stages were found to be independent of environmental pH within the range of pH 5 to 7.8. Studies on the nutritional requirements for germination revealed the need for exogenous supplies of both a carbon and nitrogen source to support germ-tube production. The ‘spore-ball phenomenon’ was investigated and a supplementary amino acid source was identified . The etiology of chalk brood is discussed in the light of these findings.

Thesis (Ph.D.) - Carleton University, 2006. / Includes bibliographical references (p. 88-121). Also available in electronic format on the Internet.