Larval development of the carrion-breeding flesh fly, Sarcophaga (Liosarcophaga) tibialis Macquart (Diptera: Sarcophagidae), at constant temperatures
- Authors: Villet, Martin H , MacKenzie, B , Muller, Wilhelmine J
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7091 , http://hdl.handle.net/10962/d1012422
- Description: Larvae of Sarcophaga (Liosarcophaga) tibialis Macquart were raised on chicken liver under six different constant temperatures. Maximum survival indicated an optimal developmental temperature of near 20°C, while trends in mortality, larval length and larval mass implied that the thermal window for successful development lay between 15°C and 30°C. Using a recently described method to estimate a simple thermal summation model, it was found that the timing of the end of the feeding phase could be estimated by a developmental zero (D0) of 5.2°C (S.E. = 1.21) and a thermal summation constant (K) of 106.4 d°C (S.E. = 8.31) and of the end of the wandering phase by D0 = 4.1°C (S.E. = 0.39) and K = 126.7 d°C (S.E. = 3.28). Published development times at constant temperatures were compiled for 19 other species of flesh flies, and the developmental constants were calculated for six species for which sufficient data were accumulated.
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- Date Issued: 2006
Finding the optimum: fluoridation of potable water in South Africa
- Authors: Muller, Wilhelmine J , Heath, R G M , Villet, Martin H
- Date: 1998
- Subjects: Water SA
- Language: English
- Type: Article
- Identifier: vital:6921 , http://hdl.handle.net/10962/d1011904
- Description: Since the South African Department of Health has tabled legislation to make fluoridation of public water supplies mandatory, the issue of whether fluoride is beneficial or harmful has, once again, become controversial in South Africa. We reviewed the literature, the experiences of fluoridation in overseas countries and the latest WHO recommendations, and have found that fluoride is desirable at certain levels, and undesirable above these. The following recommendations are made for optimum fluoride levels in South Africa's potable water: The decision to fluoridate a public water supply must be a community decision taken after public consultation. However, it can only be reached when the public is properly informed about the issue. Optimum levels of fluoride for human health range from 0.4 to 0.7 mg F/l, depending on the maximum mean annual temperature. The maximum level of 0.7 mg F/l should not be exceeded. Accordingly, it is recommended that in areas where natural fluoride concentrations in the drinking water exceed 0.7 mg F/l steps be taken to defluoridate the water. As an interim measure, a scale of temperature-adjusted optimum fluoride levels should be adopted in South Africa, rather than a single level covering the wide-ranging ambient temperatures (and corresponding consumption rates of drinking water) in the country. A sliding scale would mean that the community within a water supply region can determine its own fluoride consumption within the optimum range. Fluoridation should be considered only a short-term measure, until economic conditions are such that all South Africans have access to proper dental health care. The duration of fluoridation of a community water supply, and the level of fluoridation (within the optimum range of fluoride levels) should both be considered community decision. However, defluoridation should be a permanent necessity in those areas where the drinking water exceeds levels of 0.7 mg F/l.
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- Date Issued: 1998