Catherine L. Sole

Stacking the odds: light pollution may shift the balance in an ancient predator–prey arms race

Bat Conservation International and the South African National Research Foundation (grant number 74604).

Common Host-Derived Chemicals Increase Catches of Disease-Transmitting Mosquitoes and Can Improve Early Warning Systems for Rift Valley Fever Virus

Rift Valley fever (RVF), a mosquito-borne zoonosis, is a major public health and veterinary problem in sub-Saharan Africa. Surveillance to monitor mosquito populations during the inter-epidemic period (IEP) and viral activity in these vectors is critical to informing public health decisions for early warning and control of the disease. Using a combination of field bioassays, electrophysiological and chemical analyses we demonstrated that skin-derived aldehydes (heptanal, octanal, nonanal, decanal) common to RVF virus (RVFV) hosts including sheep, cow, donkey, goat and human serve as potent attractants for RVFV mosquito vectors. Furthermore, a blend formulated from the four aldehydes and combined with CO2-baited CDC trap without a light bulb doubled to tripled trap captures compared to control traps baited with CO2 alone. Our results reveal that (a) because of the commonality of the host chemical signature required for attraction, the host-vector interaction appears to favor the mosquito vector allowing it to find and opportunistically feed on a wide range of mammalian hosts of the disease, and (b) the sensitivity, specificity and superiority of this trapping system offers the potential for its wider use in surveillance programs for RVFV mosquito vectors especially during the IEP.

Mimicry of queen Dufour's gland secretions by workers of Apis mellifera scutellata and A. m. capensis

Abstract. The development of the Dufours gland of workers of the two honey bee races Apis mellifera scutellata and A. m. capensis was measured. The Dufours glands of A. m. capensis workers were longer and increased in length more rapidly than the glands of workers of A. m. scutellata at comparable ages. Analysis of the Dufours gland secretions of workers and queens of both races revealed that there were caste and racial differences. Secretions of queenright A. m. scutellata workers were dominated by a series of long-chain hydrocarbons. In contrast the secretions of the A. m. capensis workers both under queenright and queenless conditions were a mixture of hydrocarbons and wax-type esters, as were those of queens. Multivariate analysis of the secretion profiles indicated that laying workers of both races mimic queens. The secretions of the A. m. capensis laying workers mimicked queen secretions most closely, enabling them to act as successful social parasites.

Phylogeny and biogeography of southern African spoon-winged lacewings (Neuroptera : Nemopteridae : Nemopterinae)

Nemopteridae are a charismatic family of lacewings characterised by uniquely extended hind wings. They are an ancient widespread group in the drier regions of the world. The family comprises two subfamilies, Crocinae (thread-wings) and Nemopterinae (spoon- and ribbon-wings). The present distribution of the family has been largely influenced by the vicariant events of plate tectonics, resulting in relict populations in some parts of the world and extensive evolutionary radiations in others, particularly southern Africa where the vast majority of the species are endemic to the Western and Northern Cape Provinces of South Africa. This study aimed to establish the validity of the 11 currently recognised genera and infer their biogeographic history using molecular sequence data from four gene regions. The hypothesis that the Cape nemopterines co-evolved with certain taxa in the Cape Floristic Region was also tested. Phylogenetic analysis supports seven of the 11 currently recognised genera. The crown age of the Nemopterinae is estimated to be at ca. 145.6 Mya, indicating that the group has been present since the late Jurassic. Most of the genera appear to have diversified during the middle Eocene and into the middle Miocene (ca. 44-11 Mya) with recent rapid radiation of several of the genera occurring during the late Miocene (ca. 6-4.5 Mya). While these data support an initial radiation with the Rushioideae (Aizoaceae) it is recommended that further study including observations and gut content be carried out.

Sheep Skin Odor Improves Trap Captures of Mosquito Vectors of Rift Valley Fever

In recent years, the East African region has seen an increase in arboviral diseases transmitted by blood-feeding arthropods. Effective surveillance to monitor and reduce incidence of these infections requires the use of appropriate vector sampling tools. Here, trapped skin volatiles on fur from sheep, a known preferred host of mosquito vectors of Rift Valley fever virus (RVFV), were used with a standard CDC light trap to improve catches of mosquito vectors. We tested the standard CDC light trap alone (L), and baited with (a) CO2 (LC), (b) animal volatiles (LF), and (c) CO2 plus animal volatiles (LCF) in two highly endemic areas for RVF in Kenya (Marigat and Ijara districts) from March–June and September–December 2010. The incidence rate ratios (IRR) that mosquito species chose traps baited with treatments (LCF, LC and LF) instead of the control (L) were estimated. Marigat was dominated by secondary vectors and host-seeking mosquitoes were 3–4 times more likely to enter LC and LCF traps [IRR = 3.1 and IRR = 3.8 respectively] than the L only trap. The LCF trap captured a greater number of mosquitoes than the LC trap (IRR = 1.23) although the difference was not significant. Analogous results were observed at Ijara, where species were dominated by key primary and primary RVFV vectors, with 1.6-, 6.5-, and 8.5-fold increases in trap captures recorded in LF, LC and LCF baited traps respectively, relative to the control. These catches all differed significantly from those trapped in L only. Further, there was a significant increase in trap captures in LCF compared to LC (IRR = 1.63). Mosquito species composition and trap counts differed between the RVF sites. However, within each site, catches differed in abundance only and no species preferences were noted in the different baited-traps. Identifying the attractive components present in these natural odors should lead to development of an effective odor-bait trapping system for population density-monitoring and result in improved RVF surveillance especially during the inter-epidemic period.

Origin of Madagascan Scarabaeini dung beetles (Coleoptera: Scarabaeidae): dispersal from Africa

Madagascar, the world’s fourth largest island, has a long history of isolation (160 million years) and a wide range of climates and ecosystems which have in turn resulted in high levels of endemism across diff erent taxonomic levels. Although Madagascar has a rich dung beetle fauna that belongs to various tribes only three species of the Scarabaeini are found there, namely Scarabaeus viettei , S. radama and S. sevoistra. Th ese three species are superfi cially quite distinctive and have, consequently, had a variable taxonomic history since the fi rst one was described in 1896. Th e morphological diff erences between these species resulted in them being placed in diff erent genera at diff erent times. However, currently, based on cladistic analyses, they are all classifi ed in the genus Scarabaeus . In this study, two of the species, S. viettei and S. radama , were included in a phylogenetic analysis based on two mitochondrial gene regions — cytochrome oxidase I (COI) and 16S rRNA — and a 247 morphological and behavioural dataset of 23 members of the Scarabaeinae. A Bayesian phylogram supports the monophyly of the genus Scarabaeus , with the two species from Madagascar appearing sister to three species of Scarabaeus from south-west Africa. Estimated times of divergence based on published mutation rates of 0.012 and 0.0075 for COI indicate that a shared African/Madagascan origin occurred around 15.18 or 24.15 million years ago, respectively. Th is study is another example in support of Madagascan fauna having an African origin with colonisation having occurred via dispersal as opposed to ancient vicariant events.

Field evaluation of natural human odours and the biogent-synthetic lure in trapping Aedes aegypti, vector of dengue and chikungunya viruses in Kenya

BackgroundMethods currently used in sampling adult Aedes aegypti, the main vector of dengue and chikungunya viruses are limited for effective surveillance of the vector and accurate determination of the extent of virus transmission during outbreaks and inter - epidemic periods. Here, we document the use of natural human skin odours in baited traps to improve sampling of adult Ae. aegypti in two different endemic areas of chikungunya and dengue in Kenya – Kilifi and Busia Counties. The chemistry of the volatiles released from human odours and the Biogent (BG)-commercial lure were also compared.MethodsCotton socks and T-shirts were used to obtain natural human skin volatiles from the feet and trunk of three volunteers (volunteers 1 and 2 in Kilifi and volunteers 2 and 3 in Busia). Using Latin square design, we compared the efficacies of BG sentinel traps baited with carbon dioxide plus (a) no bait, (b) human feet volatiles, (c) human trunk volatiles each against (c) a control (Biogent commercial lure) at the two sites. Coupled gas chromatography-mass spectrometry (GC-MS) was used to identify and compare candidate attractants released by the commercial lure and human odours.ResultsAe. aegypti captured in the trap baited with feet odours from volunteer 2 and trunk odours from the same volunteer were significantly higher than in the control trap in Busia and Kilifi respectively, [IRR = 5.63, 95% CI: 1.15 - 28.30, p = 0.030] and [IRR = 3.99, 95% CI: 0.95-16.69, p = 0.049]. At both sites, Ae. aegypti captures in traps baited with either the feet or trunk odours from volunteers 1 and 3 were not significantly different from the control. Major qualitative differences were observed between the chemical profiles of human odours and the commercial BG-lure. Aldehydes, fatty acids and ketones dominated human odour profiles, whereas the BG-lure released mainly hexanoic acid.ConclusionsOur results suggest that additional candidate attractants are present in human skin volatiles which can help to improve the efficacy of lures for trapping and surveillance of Ae. aegypti.

Body temperature patterns in two syntopic elephant shrew species during winter

We measured body temperature (T(b)) in free-ranging individuals of two species of elephant shrews, namely western rock elephant shrews (Elephantulus rupestris) and Cape rock elephant shrews (E. edwardii), during winter in a winter-rainfall region of western South Africa. These syntopic species have similar ecologies and morphologies and thus potential for large overlaps in diet and habitat use. Unexpectedly, they displayed different T(b) patterns. Western rock elephant shrews were heterothermic, with all individuals decreasing T(b) below 30°C on at least 34% of nights. The level of heterothermy expressed was similar to other species traditionally defined as daily heterotherms and was inversely related to T(a), as is commonly seen in small heterothermic endotherms. In contrast, Cape rock elephant shrews rarely allowed their T(b) to decrease below 30°C. The level of heterothermy was similar to species traditionally defined as homeotherms and there was no relationship between the level of heterothermy expressed and T(a). In both species, the minimum daily T(b) was recorded almost exclusively at night, often shortly before sunrise, although in some individuals minimum T(b) occasionally occurred during the day. The interspecific variation in T(b) patterns among Elephantulus species recorded to date reiterates the importance of ecological determinants of heterothermy that interact with factors such as body mass and phylogeny.

Trapping of Rift Valley Fever (RVF) vectors using Light Emitting Diode (LED) CDC traps in two arboviral disease hot spots in Kenya

BackgroundMosquitoes’ response to artificial lights including color has been exploited in trap designs for improved sampling of mosquito vectors. Earlier studies suggest that mosquitoes are attracted to specific wavelengths of light and thus the need to refine techniques to increase mosquito captures following the development of super-bright light-emitting diodes (LEDs) which emit narrow wavelengths of light or very specific colors. Therefore, we investigated if LEDs can be effective substitutes for incandescent lamps used in CDC light traps for mosquito surveillance, and if so, determine the best color for attraction of important Rift Valley Fever (RFV) vectors.MethodsThe efficiency of selected colored LED CDC light traps (red, green, blue, violet, combination of blue-green-red (BGR)) to sample RVF vectors was evaluated relative to incandescent light (as control) in a CDC light trap in two RVF hotspots (Marigat and Ijara districts) in Kenya. In field experiments, traps were baited with dry ice and captures evaluated for Aedes tricholabis, Ae. mcintoshi, Ae. ochraceus, Mansonia uniformis, Mn. africana and Culex pipiens, following Latin square design with days as replicates. Daily mosquito counts per treatment were analyzed using a generalized linear model with Negative Binomial error structure and log link using R. The incidence rate ratios (IRR) that mosquito species chose other treatments instead of the control, were estimated.ResultsSeasonal preference of Ae.mcintoshi and Ae. ochraceus at Ijara was evident with a bias towards BGR and blue traps respectively in one trapping period but this pattern waned during another period at same site with significantly low numbers recorded in all colored traps except blue relative to the control. Overall results showed that higher captures of all species were recorded in control traps compared to the other LED traps (IRR < 1) although only significantly different from red and violet.ConclusionBased on our trapping design and color, none of the LEDs outcompeted the standard incandescent light. The data however provides preliminary evidence that a preference might exist for some of these mosquito species based on observed differential attraction to these light colors requiring future studies to compare reflected versus transmitted light and the incorporation of colored light of varying intensities.

The gut microbiomes of two Pachysoma MacLeay desert dung beetle species (Coleoptera: Scarabaeidae: Scarabaeinae) feeding on different diets

Micro-organisms inhabiting animal guts benefit from a protected and nutrient-rich environment while assisting the host with digestion and nutrition. In this study we compare, for the first time, the bacterial and fungal gut communities of two species of the small desert dung beetle genus Pachysoma feeding on different diets: the detritivorous P. endroedyi and the dry-dung-feeding P. striatum. Whole-gut microbial communities from 5 individuals of each species were assessed using 454 pyrosequencing of the bacterial 16S rRNA gene and fungal ITS gene regions. The two bacterial communities were significantly different, with only 3.7% of operational taxonomic units shared, and displayed intra-specific variation. The number of bacterial phyla present within the guts of P. endroedyi and P. striatum individuals ranged from 6–11 and 4–7, respectively. Fungal phylotypes could only be detected within the gut of P. striatum. Although the role of host phylogeny in Pachysoma microbiome assembly remains unknown, evidence presented in this study suggests that host diet may be a deterministic factor.