No abstract

No abstract

Ephoron album was the dominant summer mayfly in shallow riffles in the agricultural zone of the Valley River, Manitoba, in 1982 and 1983. There was one generation per year; eggs deposited in August hatched in late May of the following year and nymphs developed rapidly during the summer months. The eggs required a cold period to promote hatching and hatching success of eggs treated in the laboratory at −2 °C for varying periods of time was positively correlated to the length of the exposure period. No eggs hatched following exposure to 4 or 10 °C. Production for 1982 was estimated by four methods for the production interval of only 72 days: the instantaneous growth rate method (1.32 ± 0.44 g fresh dry weight∙m−2∙year−1), the Allen curve method (1.32 g∙m−2∙year−1), the removal – summation method (1.43 ± 0.41 g∙m−2∙year−1), and the size–frequency method (1.48 ± 0.51 g∙m−2∙year−1). Confidence intervals (95%) were calculated using the method of C. C. Krueger and F. B. Martin for the size–frequency estimate of production and by bootstrapping for the removal–summation and instantaneous growth estimates.

AbstractObjectiveTo assess the nutritional quality of lunchtime food consumption among elementary-school children on Prince Edward Island according to the source of food consumed (homev. school).DesignStudents completed a lunchtime food record during an in-class survey. Dietary adequacy was assessed by comparing median micronutrient intakes with one-third of the Estimated Average Requirement; median macronutrient intakes were compared with the Acceptable Macronutrient Distribution Ranges. The Wilcoxon signed rank test was used to assess differences in nutrient intakes according to source of food consumed.SettingElementary schools in Prince Edward Island, Canada.SubjectsGrade 5 and 6 students (n1980).ResultsFoods purchased at school were higher in nutrient density for ten micronutrients (Ca, Mg, K, Zn, vitamin A, vitamin D, riboflavin, niacin, vitamin B6and vitamin B12) compared with packed lunch foods from home, which were higher in three micronutrients (Fe, vitamin C and folate). School lunches provided sufficient protein but were higher in sugar and fat than home lunches. Foods brought from home were higher in carbohydrates, fibre and Na than foods purchased at school.ConclusionsThe overall nutritional quality of lunches was poor, regardless of source. A significant proportion of foods consumed by the students came from home sources; these were lower nutritional quality and were higher in Na than foods offered at school. Findings suggest that improving the dietary habits of school-aged children will require a collaborative effort from multiple stakeholders, including parents.

1. Life history patterns and production of eight shredder-detritivore species were studied in relation to the detritus dynamics of a small acidic stream in England. Mean annual detritus inputs (direct and lateral sources combined) were approximately 400 g m )2 year )1 and showed significant seasonal and annual variation. 2. Detritus standing stock did not increase significantly during times of high input, reflecting low retention efficiency. However, the mean detritus standing stock was relatively large (108 g m )2 ) reflecting a slow decomposition rate typical of acid streams. 3. Four species were univoltine with highly synchronous patterns of emergence and recruitment (Leuctra inermis, Leuctra hippopus, Capnia vidua and Amphinemura sulcicollis). Two species were univoltine with extended patterns of emergence and recruitment (Nemoura cinerea, Potamophylax cingulatus). Leuctra nigra was apparently semivoltine, while Protonemura meyeri showed two successive cohorts in the second year of the study, suggesting either bivoltinism or cohort splitting. 3. Secondary production of the dominant shredders was 1.67 g m )2 year )1 in 1997 and 1.99 g m )2 year )1 in 1998, which is low compared with other small European streams. This was probably because of an impoverished invertebrate community and poor food quality associated with acid conditions. Food availability probably did not account for the low production as the detritus standing stock far exceeded the estimated shredder ingestion of 42-50 g m )2 year )1 . 4. Despite low overall shredder production, species-specific production was high, possibly because of competitive release in this species-poor acid stream. Periods of high production and growth showed no relationship with detritus availability but were closely related to life history.