The occunence of temperature acclimation was investigated in a range of caddis species. A closed bottle method was used for the majority of the respiration experiments, a flow-through respirometer being designed for the remaining experiments. Temperature acclimation was demonstrated in eight out of twelve species studied. Increased ability to compensate was associated with increased ecological distribution. The hydropsychids were shown to have a greater ability to acclimate than polycentropodids with similar distributions. No relationship was apparent between the interspecific differences in the respiration rate and the distribution of the species. For some species maintenance at a warmer temperature for 4-5 weeks caused a decrease in the undulatory activity of the larvae when compared, at a constant temperature, with larvae maintained at a cooler temperature. For eight of the ten species for which both sets of data were obtained the metabolic and undulatory data were compatible. A relationship between undulatory activity and distribution was suggested. For two cased caddis species a positive correlation was demonstrated between the number of gills and the body weight. Maintenance at the warmer of two temperatures over a period including a moult caused an increase in the number of gills on larvae and pupae. Intraspecific differences were found in the number of gills on larvae from different field sites, the number increasing with increased stream temperature. No relationship was demonstrated between the oxygen consumption of the larvae and the number of gills. No evidence was obtained for a difference in metabolism following maintenance of larvae at fluctuating temperatures of differing amplitudes.Decreased undulatory activity was demonstrated in larvae of Hydropsyche contuberna7is maintained under conditions of greater temperature fluctuations. Field acclimatisation was demonstrated in two species, Sericostoma personatum and Potamophy7ax cingu7atus, larvae from the warmer sites having a lower respiration rate than larvae of the same species from cooler sites, when both were measured at the same temperature.

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 114-132). Description: xiii, 132 leaves : ill. (some col.), charts ; 29 cm. / Larvae of the limpets Lottia digitalis and LOffia asmi, as well as larvae of the flat abalone Halioits walallensis. develop into lecithotrophic veliger larvae and settle into benthic habitat after a breif planktonic stage. Larvae of 1. digitalis settled and metamorphosed upon rocky substrata, as well as the barnacle P. polymerus, collected from an adult habitat high in the rocky intertidal. In contrast, substrata from mid and low intertidal zones failed to induce settlement and metamorphosis in larvae of L. digitalis. These results suggest that recruitment into high intertidal habitat is driven by settlement rather than post settlement processes. New recruits within an adult habitat were most abundant low within the adult range and upon north-facing slopes of rocks. Larvae ofH walallensis that experienced a five-day extension of their competence period exhibited accelerated rates of metamorphosis, as well as accelerated juvenile growth rates, relative to larvae that were presented with settlement surfaces at initial competence.

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Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 102-110). Description: xiii, 110 leaves : ill. ; 29 cm.

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published_or_final_version / Biological Sciences / Master / Master of Philosophy

Filter-feeding black fly larvae in lake outlet streams convert suspended bacteria and algae into benthic biomass, available to fish. Positive correlations between larval abundance and both bacterioplankton and phytoplankton were significant at the p < 0.10 level among 5 outlet streams of varying trophic status in the Eastern Townships of Quebec, and either food type alone explained &sim;28% of the variance in larval abundance among streams (Chapter 1), suggesting bacterioplankton and phytoplankton to play similar roles in larval distribution. However, when larvae were removed from 3 of 6 oligotrophic outlet streams examined in the Mauricie region of Quebec, calculated ingestion rates revealed larvae to ingest roughly 20 times more phytoplankton carbon than bacterial carbon (Chapter 2). Phytoplankton ingestion rates were high enough to satisfy daily carbon requirements, but bacterivory was low (Chapter 2), indicating that bacterial biomass contributes little to black fly diets in most systems, and will be less useful than phytoplankton biomass when using food to predict larval distribution. The majority of bacteria in streams form a carbon link to fish through sediment food webs, rather than through black fly larvae.

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 52-58). Description: ix, 58 leaves : ill. ; 29 cm.

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