No description available.

Rapid bioassessment (RBA) methods have largely been used for streams and rivers, with little development of equivalent methods to be used in lakes. This has restricted the assessment of lakes because traditional methods are time- and cost-intensive. Here I show that a newly designed RBA protocol can be used to monitor a wide range of boreal shield lakes effectively. Seventy per cent of lakes with over 25% of their shoreline developed with cottages were assessed as impacted using a multimetric index. This research has built on previous knowledge, placing new emphasis on standardizing sampling efforts by depth, habitat type (cobble sediments) and sample area in lakes. My recommendations provide water resource managers with methods that can be used as a screening tool to monitor a large group of lakes affected by a variety of stressors.

No description available.

No description available.

Limited understanding of the ecology of ground-dwelling invertebrates in Tasmania has hampered our ability to assess the adequacy of forest management. This thesis documents the distributions of ground-dwelling beetle assemblages in managed, wet eucalypt forests of southern Tasmania, and explores the response of beetles to ecological gradients caused by riparian influences near small streams (since retained riparian corridors are a major conservation tool), and edge effects from recently clearfelled logging coupes. Extensive pitfall trapping using replicated transects at four sites was employed to compare the beetle fauna between five habitats: young logging regeneration, the interior of upslope mature forest, the riparian-upslope transition in mature forest interior, and across coupe edges (both into upslope mature forest and into streamside reserves). Data screening ensured that the primary transect design, which employed traps positioned at unequal distances within transects, was unlikely to produce patterning in beetle distributions attributable to spatial autocorrelation or pitfall trap depletion. Beetles responded to riparian influences, showing subtle shifts in assemblage composition, and generally reduced abundance or species richness nearer to streams. However, site differences outweighed riparian effects. Beetles assemblage composition differed substantially between young logging regeneration and mature forest: several species were identified as indicators of each habitat. Beetles responded more strongly to edge effects than to riparian influences. Depth of edge influence extended ~ 22 m into unlogged non-riparian forest, but further into streamside reserve edges (up to ~ 65 m). Four beetle species, Choleva TFIC sp 01 (Leiodidae), Decilaus nigronotatus, D. lateralis and D. striatus (all Curculionidae), were indicators of mature forest interior. A second survey compared beetles between logging regeneration, upslope mature forest interior, mature forest interior riparian areas, and streamside reserves that had been logged on both sides, in five stands of each of the four habitats. Streamside reserves (average width 40 +/-6 m (+/- 95% CI) from reserve edge to stream) supported different beetle assemblages to unlogged areas, and were probably entirely edge-effected. These results suggest that current corridor provisions, which rely heavily on riparian reserves, may be inadequate to conserve beetles dependent on mature forest interior. Reserve corridors may need to be wider, and should more often be positioned upslope away from riparian areas. Alternatively, a mix of different types of reservation strategies (e.g. conserving some contiguous blocks of mature forest in lieu of widened corridors) needs to be developed to increase the probability that edge-sensitive and mature forest specialist taxa will be conserved.

Recent phylogenetic analyses have led to a re-evaluation of metazoan relationships, resulting in the grouping a number of invertebrates known as the spiralians. They include molluscs, and share highly conserved cleavage patterns, cell lineages and embryogenesis, but exhibit a wide diversity of adult body plans. This makes them an excellent group for studying the mechanisms by which changes to developmental programs give rise to evolution of new body plans. Spiralian cleavage results in an embryo that is divided into quadrants of tiered blastomeres designated A, B, C and D, which form the left, ventral, right and dorsal regions of the embryo respectively (Verdonk and van den Biggelaar, 1983). The establishment of the dorsoventral axis and the organization of the embryo are closely linked in molluscs and involve the specification of the dorsal, D-quadrant. In equally cleaving gastropods, one macromere at the 32-cell stage is induced by the overlying micromeres to become the D-quadrant macromere, 3D (van den Biggelaar and Guerrier 1979, Arnolds et al., 1983; Boring, 1989). The 3D macromere is required for the formation of the mesendoderm, a dorsoventral cleavage pattern and the specification and organization of the ectoderm (van den Biggelaar and Guerrier 1979, Boring 1989, Damen and Dictus 1994, 1996) This thesis investigates the molecular mechanisms of gastrulation in the gastropod mollusc Haliotis asinina. In particular it focuses on the role that the 3D macromere plays in regulating the development of the molluscan embryo. The induction of the 3D-macromere was inhibited by independent treatments: first by interrupting the MAPK signalling cascade using the inhibitor U0126; and second by preventing micromere-macromere interactions with the chemical monensin. Genetic markers for morphogenetic domains were used to assess the hypothesised roles of 3D in generating the mesendodermal lineage, inducing the surrounding ectodermal micromeres, establishing the dorsoventral axis, and regulating morphogenetic movement. Microarray analysis of treated embryos was conducted to determine the role that 3D induction plays in regulating gene expression during early development. Both U0126 and monensin treatments of H. asinina embryos yielded abnormal trochophores, similar to those of other gastropods whose normal development has been perturbed by inhibiting 3D specification (Arnolds et al., 1983; Boring, 1989; Damen and Dictus, 1996a; Kühtreiber et al., 1988; Lambert and Nagy, 2003; Martindale, 1986; Martindale et al., 1985; Raven, 1976; van den Biggelaar and Guerrier, 1979). Analysing these treatments revealed that MAPK is a crucial component of the 3D induction pathway in H. asinina, as found for Ilyanassa and Tectura (Lambert and Nagy, 2003; Lambert and Nagy, 2001), with its inhibition resulting in a loss of mesendodermal patterning. The induction of the 3D-macromere results in the establishment of a molluscan organiser, which is responsible for widespread gene activation during early development and is required for proper morphogenetic movements associated with gastrulation. There appears to be similarities in the inductive processes in gastrulation between vertebrates and gastropods. In particular the patterning of the midline and flanking neuroectoderm, which is induced to form neuronal tissue by underlying mesoderm. Inhibition of 3D induction prevented neurogenesis, supporting the hypothesis of a 3D-dependant inducer of the neuroectoderm, possibly the mesodermal bands (van den Biggelaar and Dictus, 2004). The establishment of the dorsoventral axis and patterning of the gastrulating gastropod appears more complex that previously suggested. It appears that the patterning of the gastropod is compartmentalised. The 3D macromere is required for the induction of quadrant identity and patterning of the pretrochal ectoderm, and preventing 3D induction results in a radialisation of gene expression patterns. In the posttrochal ectoderm preventing 3D induction does not prevent dorsoventral patterning in at least the vegetal ectoderm. This suggests that there is either 3D independent induction or regulatory processes involved in the axial patterning of the mollusc.

This thesis describes information obtained on the structure of 5-HT-containing neurons, on the mechanisms of transport of 5-HT and its precursors into and within neurons, on the nature of the blood supply to the CNS, and on the function of 5-HT-containing neurons within the CNS of Hellix pomatia. In particular data is obtained for the giant serotonin-containing neuron (GSG) in each cerebral ganglion. Dense-cored vesicles of mean diameter 100 nm are present in the perikarya and axon branches of the GSCs. Vesicles of similar appearance are present in the presumed presynaptic endings of the GSCs. Evidence is presented which suggests that such vesicles sequester 5-HT, The fine structure of presumed presynaptic endings making synaptic connections with the GSCs is described. Following exposure to tritiated 5-HT, electron microscope autoradiography showed that silver grains, often in very high concentrations, were located over certain fine axon branches thought to be nerve endings. These processes contained small dense-cored vesicles, which were morpliologically similar to those thought to sequester 5-HT to the perikarya of the GSCs. It is suggested that re-uptake into nerve endings is a mechanism of inactivation of 5-HT in the Following exposure to tritiated 5-HTP, silver grains were observed over the perkarya of the GSCs and other known 5-HT-contalning neurons. There was no indication that 5-HTP was taken up by nerve endings or by non-nervous structures. The accumulation of tritiated tryptophan was less specific; all the neuron perikarya took up this substance. The CMS of H. pomatla is supplied by branches of the anterior aorta. Capillaries from these branches open into a, blood space which is adjacent to, and continuous over the surface of the nervous tissue. Blood passes from this space through the epineural sheath into the body cavity sinuses. Three tissue layers separate the blood spaces from the nervous tissue. These are (i) a luminal endothelium, (ii) a connective tissue layer, and (iii) glial cells. The luminal endothelium and connective tissue are freely permeable to uncharged particles of 10 nm or less. Eloctrophysiological analysis showed that each GSC sends axon branches to muscles in the lips of the animal. Selective stimulation of the GSCs resulted in an increase of electrical activity recorded from these muscles, but no change in their length. This effect was mimicked by 5-HT applied to the muscles. It is suggested that the GSC has a facilitatory effect on the lip muscle potentials.

No description available.

Thesis (M. Sc. (Zoology)) -- University of the North, 1981 / Refer to the document

Procambarus clarkii hemocytes have been shown to bind to both LPS and a mannose containing neoglycoprotein conjugated to fluorescent probes. A decrease in the observed number of fluorescent hemocytes indirectly indicated that the binding of FITC-LPS to these cells is impaired by initial incubation with LPS. Prior treatment of hemocytes with horseradish peroxidase, a mannose rich glycoprotein, decreased their capacity to bind mannose. Mannan had no inhibitory effect on the binding of either ligand. Mixed hemocytes and hemocyte subpopulations separated by buoyant density were incubated with both ligands and revealed that a subpopulation of granular hemocytes bound both LPS and mannose. These results suggest the possible presence of two different pattern recognition cell surface receptors on this subpopulation of granular hemocytes from the red swamp crayfish, Procambarus clarkii, which may specifically recognize and bind to both LPS from gram-negative bacteria and to mannose containing glycoproteins found on microbial surfaces.