The effects of low temperatures on metabolic rates in Anopheles quadriannulatus

A research submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg,in partial fulfilment of the requirements for the degree of Master of Science in Environmental Science, 2018The effects of low temperatures on the metabolic rates of Anopheles quadriannulatus were investigated by measuring the rate of carbon dioxide emission (VCO2) at different temperatures using a closed respirometry system. In general, the metabolic rates of A. quardiannulatus decreased with decreasing ambient temperatures. However, the decreases were not uniform over the temperature range of 30 °C and 10 °C. Mean VCO2 measured at 30 °C and sometimes at 25 °C, were statistically different from those measured at other temperatures. Surprisingly, at 15 °C and 10 °C, the mean VCO2 were statistically similar. It was found that metabolic rates of the mosquitoes were affected differently if a 5 °C reduction in temperature occurred at 30 °C and when it occurred at 15 °C. Thus, a 5 °C drop in temperature at 30 °C and 15 °C did not yield similar percentage decrease in metabolic rates. Age was found not to impact on the metabolism of mosquitoes except at 10 °C and 15 °C in blood fed mosquitoes (both mated and unmated). Lack of a correlation between age and metabolic rates in these mosquitoes was a result of constant body masses as mosquitoes aged. Mean VCO2 of four days old mosquitoes in different mating and feeding states were found to be significantly differently only at 10 °C. Mated and blood fed mosquitoes from this age group retained constant metabolic rates despite changes in temperature. The finding that A. quadriannulatus is not capable of significantly dropping its metabolic rates at low temperatures (15 °C-10 °C) is an indication that the species most probably lacks a physiological overwintering mechanism. Consequently, its survival and longevity is highly compromised during winter. Thus, it can be concluded that if adult A. quadriannulatus can overwinter in cooler parts of sub-Saharan regions, it does so using non-physiological mechanisms. Otherwise, this species and related members of Anopheles gambiae overwinters in developmental stages other than adulthood. In this way, these mosquitoes are able perpetuate their populations post winter season.XL201

Guidelines for restoring Lowland Sand Fynbos ecosystems

CITATION: Holmes, P.M., et al. 2022. Guidelines for restoring Lowland Sand Fynbos ecosystems. Stellenbosch: Stellenbosch Univesity, Department of Conservation Ecology and Entomology.The original publication is available at http://biodiversityadvisor.sanbi.org/planning-and-assessment/ecological-restoration/Lowland Sand Fynbos ecosystems are among the most threatened terrestrial systems in South Africa. Of the ten Sand Fynbos veld types, seven are Critically Endangered or Endangered according to the IUCN Red List of Ecosystems. They are all either poorly protected, or not protected at all in the conservation network. Sand Fynbos ecosystems harbour unique biodiversity, but owing to their lowland locations experience extensive losses to other land uses. Some natural pockets remain scattered within agricultural or urban developments. They are, however degraded due to invasive alien plants, inappropriate fire regimes or pollution and are an urgent priority to restore. National biodiversity targets aim for a minimum proportion of an ecosystem type to be retained in a natural or near-natural state. The minimum target for Sand Fynbos ecosystems is mostly 30% of the original extent – a target no longer attainable for several of these ecosystems, such as Cape Flats Sand Fynbos. For many of these precious systems, this means a necessary focus on their restoration. The purpose of these guidelines is to assist managers and landowners of degraded Sand Fynbos vegetation to restore biodiversity and contribute to the conservation of these threatened ecosystems. The guidelines outline appropriate methods to restore degraded Sand Fynbos ecosystems, based on the latest research and field trial outcomes.Hans Hoheisen Charitable TrustBiodiversity Management Branch, City of Cape TownSANBI - South African National Biodiversity InstituteHans Hoheisen Charitable TrustPublishers versio