Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis--Groningen. / Includes bibliographical references (p. 125-128).

Feeding habits of two coexisting species of Chaoborus, C.trivittatus and C.americanus, were investigated in lake and in laboratory experiments, and by an extensive survey of larval crop contents. The field study showed that C.trivittatus has a two year life cycle, migrates dielly during the summer season down to 20 m, and is the more abundant of the two Chaoborus species. C.americanus has a one year life cycle and migrates at most over a distance of only 5 m. Seasonal abundance and distribution of most plankton types found in Eunice Lake were monitored during 1971 and 1972. Zooplankton had a low standing crop and were mostly found above 6 m. Zooplankton size and swimming velocity and size of larval head parts were measured in the laboratory and, together with the above data on vertical distribution, were used to evaluate the availability of zooplankton as prey for Chaoborus. The lake and laboratory experiments showed that rates of larval feeding and digestion increase significantly with temperature. Temperature, however, does not seem to affect feeding rate of the 4th instar C.trivittatus larvae. Feeding rates increase with larval age and vary with prey type and density. From analysis of chaoborid crop contents, diet differences were found among all instars of the two species, and these were related to prey size, abundance, and distribution. The calculated percent of prey standing crop that the Chaoborus in Eunice Lake could potentially remove ranged from a minimum of 3% for nauplii to a maximum of 20% for Diaptomus kenai. Seasonal changes in Choaborus instar composition and in zooplankton species composition result in reduced predation on any single zooplankton group. The observed diet of Chaoborus larvae in Eunice Lake was shown to be closely related to the morphology of Chaoborus and their prey and to the relative distribution of predator and prey. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 216-231).

This study documents dynamic changes in the mean abundance and body size of arthropods in an ephemeral pond over the course of a summer in order to understand the nature of interactions that shape this community, and to assess the risks posed by exposure to cercariae of the entomopathogenic digenean, Plagiorchis elegans, a potential control agent for larval mosquitoes. Chironomids were the most abundant, comprising almost two-thirds of all arthropods collected; they were followed by chaoborids, the most abundant predator. Other arthropods, in decreasing order of abundance, were the ephemerids, isopods, amphipods, odonates, dytiscids, and hemipterans. Infections were found only in chironomids and were extremely rare and of low intensity, conceivably due to predation of chaoborids on cercariae and may have protected the community from exposure to these parasites. Findings are discussed in terms of using entomopathogenic digeneans as agents in the biological control of mosquitoes.

No description available.

Lake sediments contain the remains of midge communities that may be used as biological proxies for inferring past environmental changes. Freshwater midges, including Chironomidae and Chaoboridae, from two alpine tarns (Pyramid Lake and Bullwinkle Lake) in the Cassiar Mountains of northern British Columbia were used to estimate Holocene palaeotemperature changes, and more specifically, to test for the presence of the Milankovitch thermal maximum, an early Holocene warm interval coinciding with peak Holocene summer solar insolation. Mean July air temperatures were reconstructed using midge-inference models developed via weighted averaging-partial least squares (WA-PLS) regression. Cold-tolerant midge taxa dominate the stratigraphies from both Pyramid and Bullwinkle Lakes; however, warm-adapted species are more common in Bullwinkle Lake. Early Holocene warming is apparent at both lakes, however it is unclear whether this is indicative of the Milankovitch thermal maximum. A decrease in temperature occurs from 8,700-7,900 cal. yr BP at Pyramid Lake, around the same time that the 8,200 cal. yr BP cooling event occurred in the northern hemisphere. During the middle Holocene, records from Pyramid Lake indicate an overall decrease in temperature, with a short period of warmer temperatures that peak at 5,100 cal. yr BP. Temperatures fluctuate little during this time at Bullwinkle Lake. A short warming phase is apparent at both lakes during the late Holocene. July temperatures are highest at 2,000 cal. yr BP (10.5°C) in Pyramid Lake and at 1,200 cal. yr BP (13°C) in Bullwinkle Lake. Thereafter, temperatures return to what they were before the warming occurred, and at Bullwinkle Lake, vary little throughout the remainder of the Holocene.

Lake sediments contain the remains of midge communities that may be used as biological proxies for inferring past environmental changes. Freshwater midges, including Chironomidae and Chaoboridae, from two alpine tarns (Pyramid Lake and Bullwinkle Lake) in the Cassiar Mountains of northern British Columbia were used to estimate Holocene palaeotemperature changes, and more specifically, to test for the presence of the Milankovitch thermal maximum, an early Holocene warm interval coinciding with peak Holocene summer solar insolation. Mean July air temperatures were reconstructed using midge-inference models developed via weighted averaging-partial least squares (WA-PLS) regression. Cold-tolerant midge taxa dominate the stratigraphies from both Pyramid and Bullwinkle Lakes; however, warm-adapted species are more common in Bullwinkle Lake. Early Holocene warming is apparent at both lakes, however it is unclear whether this is indicative of the Milankovitch thermal maximum. A decrease in temperature occurs from 8,700-7,900 cal. yr BP at Pyramid Lake, around the same time that the 8,200 cal. yr BP cooling event occurred in the northern hemisphere. During the middle Holocene, records from Pyramid Lake indicate an overall decrease in temperature, with a short period of warmer temperatures that peak at 5,100 cal. yr BP. Temperatures fluctuate little during this time at Bullwinkle Lake. A short warming phase is apparent at both lakes during the late Holocene. July temperatures are highest at 2,000 cal. yr BP (10.5°C) in Pyramid Lake and at 1,200 cal. yr BP (13°C) in Bullwinkle Lake. Thereafter, temperatures return to what they were before the warming occurred, and at Bullwinkle Lake, vary little throughout the remainder of the Holocene.

Lake sediments contain the remains of midge communities that may be used as biological proxies for inferring past environmental changes. Freshwater midges, including Chironomidae and Chaoboridae, from two alpine tarns (Pyramid Lake and Bullwinkle Lake) in the Cassiar Mountains of northern British Columbia were used to estimate Holocene palaeotemperature changes, and more specifically, to test for the presence of the Milankovitch thermal maximum, an early Holocene warm interval coinciding with peak Holocene summer solar insolation. Mean July air temperatures were reconstructed using midge-inference models developed via weighted averaging-partial least squares (WA-PLS) regression. Cold-tolerant midge taxa dominate the stratigraphies from both Pyramid and Bullwinkle Lakes; however, warm-adapted species are more common in Bullwinkle Lake. Early Holocene warming is apparent at both lakes, however it is unclear whether this is indicative of the Milankovitch thermal maximum. A decrease in temperature occurs from 8,700-7,900 cal. yr BP at Pyramid Lake, around the same time that the 8,200 cal. yr BP cooling event occurred in the northern hemisphere. During the middle Holocene, records from Pyramid Lake indicate an overall decrease in temperature, with a short period of warmer temperatures that peak at 5,100 cal. yr BP. Temperatures fluctuate little during this time at Bullwinkle Lake. A short warming phase is apparent at both lakes during the late Holocene. July temperatures are highest at 2,000 cal. yr BP (10.5°C) in Pyramid Lake and at 1,200 cal. yr BP (13°C) in Bullwinkle Lake. Thereafter, temperatures return to what they were before the warming occurred, and at Bullwinkle Lake, vary little throughout the remainder of the Holocene. / Irving K. Barber School of Arts and Sciences (Okanagan) / Earth and Environmental Sciences, Department of (Okanagan) / Graduate