No description available.

Habitat partitioning was studied in a community of passerine birds in the Virgin River Valley of southwestern Utah. Ten habitat structure variables were measured for each of 24 species of passerine birds and several multivariate statistical techniques were used to determine the extent of habitat partitioning. Ordinations of species distributions along known environmental gradients were constructed using Principal Component Analysis and Stepwise Discriminant Analysis. Stepwise Discriminant Analysis was also used to determine which habitat variables were important in species separation. It was found that percent canopy cover was the most important variable. Two hundred seventy six pairs of species were analyzed using Multivariant Analysis of Variance. Of these, 272 were found to inhabit significantly different parts of the environment. Qualitative analysis of the remaining four pairs also showed effective niche partitioning.

No description available.

No description available.

A phenological model of gypsy moth egg development is proposed that distinguishes three phases of egg development, prediapause, diapause and postdiapause. A technique of measuring respiration rates of individual eggs was developed and respiration rate was used as a physiological variable to distinguish the phases. The pattern of respiration rate provided strong evidence in support of three distinct developmental phases. Respiration rate developed embryos declined sharply as prediapause was entered and rose sharply when diapause was completed. When the effect of age on respiration rate was removed, temperature had a uniform effect on respiration rate throughout the egg stage. A 10°C decrease in temperature caused an approximate 0.4 fold decrease in respiration rate, indicating that eggs in diapause are as equally responsive to temperature as egg in a nondiapause phase. Developmental rate in prediapause was strongly temperature-dependent, and the relationship was described by a non-linear function. Prediapause duration was approximately 13 days at 31°C. The depletion of stored triglycerides was strongly linked to the completion of prediapause. Developmental rate in postdiapause was found to be temperature- and age-dependent. Developmental response to temperature was relatively weak and linear at the onset of postdiapause. As postdiapause advanced, the response became stronger and non-linear. The temperature- and age-dependent developmental response was fully described by the temperature-dependent developmental response at the onset of postdiapause, and by a temperature-dependent rate change parameter. / Ph. D.

M.S.

Master of Science

Respiration rates and changes in the amount of nutrients in queen-laid and worker-laid eggs of the honey bee, <I>Apis mellifera</I> L., were determined for the 3 days of embryonic development. Respiration was quantified by measuring the amount of CO₂ produced during 13 hr of artificial incubation at four temperature treatments: 28°C, 31°C, 34°C, 36°C (± 0.5°C). The amounts of lipids and carbohydrates were also quantified in the eggs of queens and laying workers on day 1, 2 and 3 using high performance thin layer chromatography. The mean respiration rate for fertilized and unfertilized eggs from queens was 0.1 ± 0.0 µL CO₂/hr/egg, the same as the mean respiration rate obtained for unfertilized eggs from laying workers. The results of carbohydrate analysis showed a total of 2.4 ± 0.6 µg/egg total sugars in the fertilized eggs of queens, an equivalent of 8.3% on a dry weight basis, while unfertilized eggs contained a total of 1.4 ± 0.4 µg/egg total sugars, equivalent of 6.3% on a dry weight basis. Total lipids, excluding fatty acids, were 10.7 ± 6.1 µg/egg (37.4%) for fertilized eggs and 8.4 ± 1.3 µg/egg (40.8%) for unfertilized eggs. The respiration rate at 34°C was 0.17 ± 0.01 µL CO₂/hr/egg on day 1, the same as day 1 at 36°C. Day 2 respiration rates were 0.13 ± 0.04 µL CO₂/hr/egg and 0.15 ± 0.01 µL CO₂/hr/egg, respectively. On day three, 0.22 ± 0.01 µL CO₂/hr/egg was recorded at 34°C and 0.24 0.01 µL CO₂/hr/egg at 36°C. At low temperatures of 28°C and 31°C, a respiration rate of 0.12 ± 0.01 µL CO₂/hr/egg was recorded on day 1, for eggs held at both temperatures. Day 2 results were 0.07 ± 0.01 µL CO₂/hr/egg at 28°C and 0.11 ± 0.01 µL CO₂/hr/egg at 31°C, while 0.07 ± 0.01 and 0.12 ± 0.01 µL CO₂/hr/egg, respectively, were measured on day 3. Mortality results, as indicated by pre-emergence embryos, showed that 75% developed at 34°C compared to 37.5% at 36°C. Low temperatures of 28°C had 12.5% developing to pre-emergence stage while 50% developed at 31°C. Respiratory results showed significant differences (p=0.05) between the different days of incubation and temperature treatments, respectively. No significant difference was observed between the fertilized eggs and unfertilized eggs from queens at the same temperature treatment. The comparison of unfertilized eggs from queens and those from laying workers also showed no significant difference. The regression (R²=0.65) was significant (P=0.05) when CO₂ output on all the days and temperature treatments were compared. The amount of nutrients in the eggs of queens and those of laying workers, were significantly different (P=0.05) depending on egg type and age. No significant difference was observed between the colonies headed by queens or those of laying workers. Although the queen-laid eggs showed a relatively higher mean value for carbohydrates than worker-laid eggs, the reverse was the case for lipids. On comparing the amount of nutrients per unit weight for queen-laid and worker-laid eggs, no significant differences were observed. From the results obtained, inferences were made about the natural differences between the eggs from queens, and those produced by laying workers. / Master of Science

Catfish aquaculture remains the largest sector of the U.S. aquaculture industry, grossing ~$447 million in sales in 2022. Producers are plagued by annual losses associated with the trematode Bolbophorus damnificus. Management focuses on controlling the snail intermediate hosts using copper sulfate. Herein, the effects of copper on larval stages of the trematode Drepanocephalus spathans and Austrodiplostomum compactum eggs were investigated. Results indicate copper treatments currently used to control snails are ineffective at precluding hatching of trematode eggs. Higher doses prevented trematode eggs from hatching, although these levels are likely impractical in a commercial setting. A second study investigated the effects of temperature on miracidia of D. spathans development and hatching. Eggs were collected from digesta of double-crested cormorants and stored at 4 °C until analysis. Data generated from these studies indicate D. spathans eggs hatch from 12–22 days after removal from cold storage to 26–30 °C, but hatching was not observed at temperatures <20 °C.

Thesis (M. Tech.(Environmental Health)) -- Central University of Technology Free State, 2005 / In developing countries such as South Africa commercial chicken farmers produce the majority of eggs, approximately 5.8kg of eggs per capita per annum. Despite this, many people, especially in rural and marginal-urban areas, still consume eggs produced by backyard systems. Backyard systems are characterised by fragmented and small-scale production units that require minimal management and chickens are often unhoused or poorly housed. In most cases, eggs from backyard systems are laid in nests in poor hygienic condition. Eggs are a cheap, readily available and a good source of animal protein and are consumed by the majority of the people in the community, including the young, the old and people with HIV/AIDS. With little information available regarding the microbiological quality of eggs produced by backyard chickens in Southern Africa, the risks posed by these eggs to consumers are unknown. In this study the microbiological quality of eggs from randomly selected household near Hennenman keeping backyard chickens was determined. The study was done over three seasons which included the cold-dry (May-July), mild-dry (October- February) and the warm-wet (August-September) seasons. The following organisms were isolated: Salmonella spp., Pseudomonas spp., Staphylococcus spp., Escherichia coli and Total Coliforms. Staphylococcus spp. was further characterised to species level. Most of the species were of human origin, with the exception of only two species, S. hyicus and S. lentus, which have previously been associated with chickens. Furthermore, questionnaires were administered to the backyard chicken keepers to assess their knowledge regarding chicken keeping and nest hygiene, the proper method of egg collection and storage, and the preparation of eggs. The decrease of vitamins and Staphylococcus spp. occurring during different preparation methods (scrambling, frying and boiling) was also determined. The results obtained showed that the eggshells were more contaminated than the egg contents. This had been expected as the eggshell is more in contact with the external environment than the egg contents are. Faecal contaminants (Salmonella spp., Escherichia coli and Total Coliforms) were present in both the eggshell and the egg contents during all seasons and this could be attributed to the infrequent cleaning of chicken nests as ascertained from the questionnaires. From the vitamin analysis it was observed that backyard-produced eggs had lower concentrations of vitamins A and E compared to commercially-produced eggs. When determining the best preparation method, causing the most degradation of Staphylococcus spp., while on the other hand preserving vitamins, it was found that scrambling was the best method, followed by the frying and boiling methods respectively.