Vector competence of South African Culicoides species for bluetongue virus serotype 1 (BTV-1) with special reference to the effect of temperature on the rate of virus replication in C. imicola and C. bolitinos

Abstract. The oral susceptibility of 22 South African livestock associated Culicoides species to infection with bluetongue virus serotype 1 (BTV‐1) and its replication rate in C. imicola Kieffer and C. bolitinos Meiswinkel (Diptera: Ceratopogonidae) over a range of different incubation periods and temperatures are reported. Field‐collected Culicoides were fed on sheep blood containing 7.5 log₁₀TCID₅₀/mL of BTV‐1, and then held at constant different temperatures. Virus replication was measured over time by assaying individual flies in BHK‐21 cells using a microtitration procedure. Regardless of the incubation temperatures (10, 15, 18, 23.5 and 30°C) the mean virus titre/midge, infection rates (IR) and the proportion of infected females with transmission potential (TP = virus titre/midge ≥ 3 log₁₀ TCID₅₀) were found to be significantly higher in C. bolitinos than in C. imicola. Results from days 4–10 post‐infection (dpi), at 15–30°C, shows that the mean IR and TP values in C. bolitinos ranged from 36.7 to 87.8%, and from 8.4 to 87.7%, respectively; in C. imicola the respective values were 11.0–13.7% and 0–46.8%. In both species the highest IR was recorded at 25°C and the highest TP at 30°C. The time required for the development of TP in C. bolitinos ranged from 2 dpi at 25°C to 8 dpi at 15°C. In C. imicola it ranged from 4 dpi at 30°C to 10 dpi at 23.5°C; no individuals with TP were detected at 15°C. There was no evidence of virus replication in flies held at 10°C. When, at various points of incubation, individual flies were transferred from 10°C to 23.5°C and then assayed 4–10 days later, virus was recovered from both species. The mean virus titres/midge, and proportion of individuals with TP and IR, were again significantly higher in C. bolitinos than in C. imicola. Also the infection prevalence in C. magnus Colaço was higher than in C. imicola. Low infection prevalences were found in C. bedfordi Ingram & Macfie, C. leucostictus Kieffer, C. pycnostictus Ingram & Macfie, C. gulbenkiani Caeiro and C. milnei Austen. BTV‐1 was not detected in 14 other Culicoides species tested; however, some of these were tested in limited numbers. The present study indicates a multivector potential for BTV transmission in South Africa. In C. imicola and C. bolitinos the replication rates are distinct and are significantly influenced by temperature. These findings are discussed in relation to the epidemiology of bluetongue in South Africa.     

Filamentous freshwater macroalgae in South Africa — a literature review and perspective on the development and control of weed problems

Studies on freshwater filamentous algae have not been undertaken in South Africa for some thirty years. Early investigations were mainly of a taxonomic nature and ecological information is virtually non-existent. However, in the recent years the spread of urban settlement and increasing demand for both industrial and domestic water have highlighted the problems facing current water supplies. Irrigation systems in particular have suffered increasing interferences from filamentous algal blooms, mainly Cladophora glomerata. As nutrient loads have increased in impoundments and rivers, the presence of this alga has become more obvious, causing decreased water flow in canals and an escalation in costs associated with its control. Copper sulphate and predosing with commercial sulphuric acid to reduce pH are now the commonest control method in most of the irrigation systems. A synopsis of current conditions is presented and proposed avenues of research are discussed.     

IMPORTANCE OF PHYSICAL VARIABLES ON THE SEASONAL DYNAMICS OF EPILITHIC ALGAE IN A HIGHLY SHADED CANYON STREAM1

The seasonal abundance of epilithic algae was correlated with major physico-chemical parameters in a first-order, heavily shaded stream in northern Arizona. Diatoms made up over 85%, by numerical abundance, of the epilithon community Light energy, water temperature, and stream discharge were most highly correlated with seasonal abundance of epilithic diatom taxa when analyzed with stepwise multiple regression. None of the chemical variables measured in the study (NO₃-N, O-PO₄, SiO₂, including PH) was found to be significantly correlated with the seasonal community structure of epilithic diatoms. Total diatom cell densities showed a significant negative correlation to stream bed light energy. Likewise, total diatom cell densities along a transect in the stream bed showed a negative correlation to current velocity during those months when base flow was low and stable, and current velocity was ≤25 cm·sec-¹. Most diatom taxa had highest cell densities at temperatures < 16°C and at daily mean stream bed light levels < 400 μE·m^?2·s^?1. Highest cell densities of green algae occurred at temperatures between 6–16°C and at daily mean stream bed light levels of > 400 μE·m^?2·s^?1. Blue-green algae (cyanobacteria) grew best at the highest recorded water temperatures and daily mean stream bed light energy (16–20°C and 900–1200 μE·m^?2·s^?1). Abrupt increases in NO₃-N coincided with a brief pulse of Nostoc pruniforme colonies during June, and leaf drop from Alnus oblongifolia during October.     

The thermal physiology of Stenopelmus rufinasus and Neohydronomus affinis (Coleoptera: Curculionidae), two biological control agents for the invasive alien aquatic weeds,Azolla filiculoides and Pistia stratiotes in South Africa

Water lettuce, Pistia stratiotes, and red water fern, Azolla filiculoides, are floating aquatic macrophytes that have become problematic in South Africa. Two weevils, Neohydronomus affinis and Stenopelmus rufinasus, are successful biological control agents of these two species in South Africa. The aim of this study was to investigate the thermal requirements of these two species to explain their establishment patterns in the field. Laboratory results showed that both weevils are widely tolerant to cold and warm temperatures. The critical thermal minima (CT_min) of N. affinis was determined to be 5.58?±?0.31°C and the critical thermal maxima (CT_max) was 44.52?±?0.27°C, while the CT_min of S. rufinasus was 5.38?±?0.33°C and the CT_max?44.0?±?0.17°C. In addition, the lower lethal temperatures were ?9.85?±?0.06°C for N. affinis and ?6.85?±?0.13°C for S. rufinasus, and the upper lethal temperatures were 42.7?±?0.85°C for N. affinis and 41.9?±?2.52°C S. rufinasus. Using the reduced major axis regression method, the development for N. affinis was described using the formula y?=?12.976x?+?435.24, while the development of S. rufinasus was described by y?=?13.6x?+?222.45. These results showed that S. rufinasus develops twice as fast as N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. These results suggest that both species should not be limited by cold winter, nor warm summer temperatures, and should establish throughout the ranges of the weeds in South Africa.     

A new species of Crossidium (Pottiaceae,Bryophyta) from South Africa

Abstract

A new species of Crossidium (Pottiaceae, Bryophyta), C. karoo, is described for South Africa. It uniquely differs from congeners in tight encapsulation of the photosynthetic filaments by the clasping upper lamina.     

First record of a spiral form of Aulacoseira,A. ambigua f. japonica (F.Meister) Tuji & D.M.Williams,in South African fresh waters

Water quality and algal populations in the Vaal River Barrage Reservoir have been monitored extensively for many decades, because of its importance as a water source for the most densely populated area in South Africa. Although Aulacoseira granulata (Ehrenberg) Simonsen is frequently found and at it times dominates algal assemblages in the Barrage, Aulacoseira ambigua (F.Meister) Tuji & D.M.Williams has never before been recorded at this locality. During a countrywide proficiency-testing scheme for algae counting, coordinated by Rand Water, spiral-shaped diatom colonies with distinctly curved cells were detected during May 2015. Upon investigation, it was found that the spiral colonies were Aulacoseira ambigua f. japonica, its presence in the fresh waters of South Africa being recorded for the first time. Since their first appearance during May 2015, colonies of Aulacoseira ambigua f. japonica have been constantly present in the surface waters of the Barrage. Their presence at this site can be linked to increasing eutrophication in the Vaal River, because the spiral form is known to prefer eutrophic conditions. Centric diatoms rarely form spiral colonies and there is some confusion in the literature as to the identity of this particular form, therefore in this paper we discuss this taxon, its nomenclature and ecological significance.     

The species of the genus Micrambe Thomson 1863, from South Africa (Coleoptera: Cryptophagidae)

The 22 species of the genus Micrambe Thomson known from South Africa are analyzed and revised. Micrambe danielssoni sp. nov is described. Following a detailed study of the type material in different entomological collections, the status of two taxa is revised and two new synonymies are proposed: Micrambe kolbei Grouvelle 1908, syn. nov. for Micrambe minuta Grouvelle 1908, and Micrambe similis Bruce 1957, syn. nov. for Micrambe peringueyi Grouvelle 1908. A lectotypus is designated for one taxon: Micrambe capensis (Redtenbacher 1867). A key to all the species occurring in South Africa is presented.     

Responses of attached algal communities to termination of thermal pollution

Post-thermal recovery of attached algae in six artificial streams subjected to three years of thermal pollution was studied for 20 months. Vaucheria, which had been reduced or eliminated by elevated temperatures in some of the streams, returned to pre-thermal abundance within one month. Schizothrix, which had been greatly augmented by heating, decreased to pre-thermal abundance within two months. However, Schizothrix also demonstrated a decreasing tendency to reappear during the late summer at above normal levels, in the stream previously heated the most (12.5 ° C). The epilithic red algae, Rhodochorton and Tuomeya were absent for three years in the stream heated 12.5 ° C above ambient, but returned to pre-thermal levels in three and five months, respectively, when the heating was terminated.     

Eine neue tropische Unterart von Keratella cochlearis (Rotatoria)

A new subspecies of Keratella cochlearis, viz. Keratella cochlearis pachyacantka is described. It has been recorded from Africa and South America.     

Distribution of cancer mortality rates by province in South Africa

IntroductionCancer mortality rates are expected to increase in developing countries. Cancer mortality rates by province remain largely unreported in South Africa. This study described the 2014 age standardised cancer mortality rates by province in South Africa, to provide insight for strategic interventions and advocacy.Methods2014 deaths data were retrieved from Statistics South Africa. Deaths from cancer were extracted using 10th International Classification of Diseases (ICD) codes for cancer (C00-C97). Adjusted 2013 mid-year population estimates were used as a standard population. All rates were calculated per 100 000 individuals.ResultsNearly 38 000 (8%) of the total deaths in South Africa in 2014 were attributed to cancer. Western Cape Province had the highest age standardised cancer mortality rate in South Africa (118, 95% CI: 115–121 deaths per 100 000 individuals), followed by the Northern Cape (113, 95% CI: 107–119 per 100 000 individuals), with the lowest rate in Limpopo Province (47, 95% CI: 45–49 per 100 000). The age standardised cancer mortality rate for men (71, 95% CI: 70–72 per 100 000 individuals) was similar to women (69, 95% CI: 68–70 per 100 000). Lung cancer was a major driver of cancer death in men (13, 95% CI: 12.6–13.4 per 100 000). In women, cervical cancer was the leading cause of cancer death (13, 95% CI: 12.6–13.4 per 100 000 individuals).ConclusionThere is a need to further investigate the factors related to the differences in cancer mortality by province in South Africa. Raising awareness of risk factors and screening for cancer in the population along with improved access and quality of health care are also important.     

Regulation of body temperature in the white shark, Carcharodon carcharias

Stomach temperatures of three white sharks, Carcharodoncarcharias, (one reported previously and two new individuals) were intermittently recorded by acoustic telemetry at the South Farallon Islands, central California. Temperature profiles of the water column were obtained concurrently. Stomach temperatures were elevated over ambient water temperatures by as much as 14.3 °C. Stomach temperatures varied within a narrow range while ambient water temperature fluctuated over a much larger range, showing that this species regulates its body temperature. These data, in combination with previous work on the physiology and anatomy of white sharks, indicate that the white shark is endothermic. It appears that the heat retention system in lamnid sharks has allowed them to inhabit cold water and remain active predators of swift and agile prey. Accepted: 17 February 1997     

THE EFFECT OF CONSTANT TEMPERATURES ON THE HATCHING OF EGGS AND SURVIVAL OF THE FRESHWATER SNAIL BIOMPHALARIA GLABRATA (SAY)

SUMMARY

The incubation period and percentage hatching of eggs of pigmented and unpigmented Biomphalaria glabrata at constant temperatures were investigated in the range 14 °C to 34 °C. In order to determine the influence of extreme temperatures on adult snails, specimens of the same species were exposed to 0 °C and 40 °C for selected time periods. The results indicate that sustained temperatures below 16 °C and above 32 °C are detrimental to the development and hatching of B. glabrata embryos. The optimum temperatures for incubation period and hatching differ from each other. As far as temperature is concerned, this foreign snail species should be capable of successfully colonizing the warmer parts of southern Africa.     

Predicting the distribution of Eccritotarsus catarinensis, a natural enemy released on water hyacinth in South Africa

Water hyacinth [Eichhornia crassipes (Mart.) Solms (Pontederiaceae)] is the most damaging aquatic weed in South Africa, where five arthropod biological control agents have been released against it. The most recent introduction of Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) has failed to establish permanent populations at a number of sites in South Africa where water hyacinth is a problem. Cold winter temperatures at these sites are assumed to be the reason for these establishment failures. This assumption was tested by investigating the thermal physiology of the mirid, then incorporating these data into various predictive distribution models. Degree‐day models predict 3–14 generations per year at different localities in South Africa, and five generations at a Johannesburg site where the mirid failed to overwinter. The inability to develop sufficiently rapidly during winter months may hinder overwintering of this insect, which was predicted to develop through only one generation during the winter months of April to August in Johannesburg. A CLIMEX model also showed that cold stress limits the mirid's ability to overwinter in the interior of the country, while determination of the lower lethal limit (–3.5 °C) and critical thermal minimum (1.2 ± 1.17 °C) also indicated that extreme temperatures will limit establishment at certain sites. It is concluded that E. catarinensis is limited in its distribution in South Africa by low winter temperatures.     

The oral susceptibility of South African field populations of Culicoides to African horse sickness virus

Twenty‐two isolates of African horse sickness virus (AHSV), representing its distinct serotypes, geographical and historical origins, were fed to three populations of South African livestock‐associated Culicoides spp. (Diptera, Ceratopogonidae). Infective blood meals included 12 recent isolates, nine historical reference strains and one live attenuated vaccine strain serotype 7 (AHSV‐7) of the virus. Field‐collected midges were fed through a chicken‐skin membrane on sheep blood spiked with one of the viruses, which concentrations ranged from 5.4 to 8.8 log₁₀TCID₅₀/mL of blood. After 10 days incubation at 23.5°C, AHSV was isolated from 11 Culicoides species. Standard in vitro passaging of AHSV‐7, used for the preparation of live attenuated vaccine, did not reduce its ability to infect Culicoides species. Virus recovery rates in orally infected Culicoides midges differed significantly between species and populations, serotypes, isolates and seasons. Significant variations in oral susceptibility recorded in this study emphasize a complex inter‐relationship between virus and vector, which is further influenced by multiple intrinsic and extrinsic factors. As it is not possible to standardize all these factors under laboratory conditions, conclusive assessment of the role of field‐collected Culicoides midges in the transmission of orbiviruses remains problematic. Nevertheless, results of this study suggest the potential for multi‐vector transmission of AHSV virus in South Africa.     

LIGHT,TEMPERATURE AND PHOTOPERIOD AS FACTORS CONTROLLING REPRODUCTION IN ULOTHRIX ZONATA (ULVOPHYCEAE)1

In many lakes in the northern United States and Canada the filamentous green alga Ulothrix zonata (Weber and Mohr) Kütz grows abundantly in early spring in shallow waters. Asexual reproduction occurs by formation of quadriflagellate zoospores which disrupt, the integrity of the cells upon release causing the filament to disintegrate. Study of the effects of 100 different combinations of irradiance, temperature and photoperiod revealed that zoospore formation is favored by high temperatures near 20°C, high light levels of 520 μE·m^?2·s^?1 and photoperiods of either short day (8:16 h light-dark) or long day cycles (16:8 h light-dark). Zoospore formation is minimal under conditions of low temperature (5°C), low irradiance (32.5 μE·m^?2·s^?1) and neutral day-lengths (12:12 h light-dark). These observations explain the decline in U. zonata biomass when water temperatures rise above 10° C. The combined effect of rising water temperatures and increasing daylengths causes progressively more filaments to switch from vegetable growth to zoospore production resulting in an increasing loss of biomass.     

ITS1 sequences of type specimens of Gigartina and Sarcothalia and their significance for the classification of South African Gigartinaceae (Gigartinales,Rhodophyta)

Uncertainties about the identity of type specimens of red algae have frequently led to taxonomic and nomenclatural confusion. A procedure for extracting PCR-amplifiable DNA from formalin-fixed material and herbarium specimens was used to investigate the taxonomic status of several South African Gigartinaceae. We compared nucleotide sequences in the internal transcribed spacer 1 (ITS1) region in type specimens and other historically important collections presently referred to Gigartina bracteata, G. radula and G. stiriata. The following opinions are supported: (1) Fucus bracteatus S.G. Gmelin, Chondrodictyon capense Kützing and Iridaea clathrata Decaisne represent a single species of South African Gigartina (G. bracteata (S.G. Gmelin) Setchell & Gardner) in which the disintegration of tetrasporangial sori results in a reticulate thallus. (2) Mastocarpus polycarpus Kützing, M. incrassatus Kützing and Iridaea lapathifolia Kützing represent a single species of South African Gigartina (G. polycarpa (Kützing) Setchell & Gardner) that has often, but erroneously, been called G. radula (Esper) J. Agardh. (3) Mastocarpus verrucosus Kützing is a later heterotypic synonym of Iridaea papillosa Bory (Sarcothalia papillosa (Bory) Leister) and was based on material that probably came from southern South America rather than from South Africa, the provenance given by Kützing. (4) Fucus stiriatus Turner and Sphaerococcus burmannii C. Agardh represent a single species of South African Sarcothalia (S. stiriata (Turner) Leister).     

Seasonal changes in habitat preferences of two closely related millipede species

The habitat preferences of two closely related millipede species, Centrobolus richardii and C. fulgidus, were investigated on three different seral stages of a coastal dune forest successional sere north of Richards Bay, South Africa. Fixed‐width transects were used to survey millipedes in three habitats of different ages. Habitat preference occurred on both inter‐ and intra‐site levels and was influenced by season. A habitat shift was recorded for C. richardii, while C. fulgidus was dormant during the winter months, reflecting two different strategies used by these closely related species to meet their resource requirements. Successional changes previously reported are masked by these differential responses.     

Models of development for blowfly sister species Chrysomya chloropyga and Chrysomya putoria

Abstract Developmental curves for the sister species Chrysomya chloropyga (Wiedemann, 1818) and Chrysomya putoria (Wiedemann, 1830) (Diptera: Calliphoridae) were established at eight and 10 different constant temperatures, respectively, using developmental landmarks and body length as measures of age. The thermal summation constants (K) and developmental threshold (D₀) were calculated for five developmental landmarks using a previously described method. Isomorphen and isomegalen diagrams were also constructed for the purpose of estimating postmortem intervals (PMIs). Chrysomya chloropyga had an average developmental threshold value (D₀) of 10.91 °C (standard error [SE] = 0.94 °C, n = 5), significantly lower than that of C. putoria (13.42 °C, SE = 0.45 °C, n = 5) (paired t‐test: t = ? 4.63, d.f. = 8, P < 0.00). Similarly, K values for C. chloropyga were larger than those for C. putoria for all developmental events except onset of the wandering phase. These are the first data that can be used to calculate minimum PMIs and predict population growth of C. chloropyga and C. putoria in Africa; the data indicate that developmental data for one of these species cannot be used as surrogate data for the sister species.     

Thermal Acclimation of Respiration and Photosynthesis in the Marine Macroalga Gracilaria lemaneiformis (Gracilariales,Rhodophyta)

The responses of respiration and photosynthesis to temperature fluctuations in marine macroalgae have the potential to significantly affect coastal carbon fluxes and sequestration. In this study, the marine red macroalga Gracilaria lemaneiformis was cultured at three different temperatures (12, 19, and 26°C) and at high‐ and low‐nitrogen (N) availability, to investigate the acclimation potential of respiration and photosynthesis to temperature change. Measurements of respiratory and photosynthetic rates were made at five temperatures (7°C–33°C). An instantaneous change in temperature resulted in a change in the rates of respiration and photosynthesis, and the temperature sensitivities (i.e., the Q₁₀ value) for both the metabolic processes were lower in 26°C‐grown algae than 12°C‐ or 19°C‐grown algae. Both respiration and photosynthesis acclimated to long‐term changes in temperature, irrespective of the N availability under which the algae were grown; respiration displayed strong acclimation, whereas photosynthesis only exhibited a partial acclimation response to changing growth temperatures. The ratio of respiration to gross photosynthesis was higher in 12°C‐grown algae, but displayed little difference between the algae grown at 19°C and 26°C. We propose that it is unlikely that respiration in G. lemaneiformis would increase significantly with global warming, although photosynthesis would increase at moderately elevated temperatures.