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Female-biased population sex ratios in butterflies arise as a consequence of infection by maternally-transmitted endosymbionts that manipulate host sex ratio in order to maximize their transmission down the generations. A critical step toward understanding the host/male-killer relationship as well as the evolutionary consequences of male-killing is to provide accurate estimations for the population sex ratios in the host species. There are two ways to perform this: first, through counting the numbers of males and females in wild collections, and second, through the molecular screening of collected females for bacterial infection, using the PCR. In this paper, we compare the estimations of the two methods in the case of the queen butterfly Danaus chrysippus at Uganda and Sudan. We concluded that molecular screening is the most accurate approach to assess the population sex ratio. Moreover, a theoretical argument has been presented at the end of this article to explain why the bacterial prevalence approach avoids the inherent collection bias that is suffered by the sex ratio method.

Species with extremely female-biased sex ratios are expected to show alteration in the normal sex roles, as a response to male scarcity. The tropical butterfly Acraea encedon is known to be infected with a male-killing bacterium of the genus Wolbachia, which has led to severe sex ratio distortion in some populations where more than 95 % of wild females are infected with the male-killer. Thus, the aggregation of female A. encedon at resource-free landmarks has been interpreted as “female lekking” behaviour, a sex role-reversed form of lekking normally seen in males of many animals. For this paper, sites in Uganda where female-leks have previously been reported (in 1998) were revisited and surveyed for both sex ratio and bacterial prevalence, for 3 years (2005–2007). The hypothesis of sex role-reversal in A. encedon was evaluated in light of the field data obtained. The study concluded that the response of host populations to the gradual spread of the male-killer toward fixation occurs initially at the behavioural level, as sex role-reversal, and finally at the demographic level, by succumbing to extinction.

Many neurotoxic polypeptides (NPs) from venom of the scorpion Leiurus quinquestriatus (LqV) have been isolated and functionally characterized that were found to block voltage-activated ion channels in excitable tissues in both mammals and insects. This study aims to reveal the time-dependent alternations of these electrolytes in plasma that induced by (LqV) in vivo. Rabbits were injected subcutaneously with a sub-lethal dose of approximately 0.12 mg/km body weight of crude (LqV). Photometric techniques have been used to monitor changes in the concentrations of Na⁺, K⁺, and Ca⁺⁺ in plasma six times; the first sample considered as control, the other five samples were collected in 36 minutes interval (after LqV injection). Correlation and regression analysis have shown that potassium and Calcium concentration tended to decrease (r=-0.706) and (r=-0.586) respectively whereas, concentration of Sodium tended to increase (r=0.635). Percentage of concentration change from control showed highly significant fluctuation during the first two hours, sodium was highly decreased by -72.29% below control 36 minutes after injection, for potassium and calcium, concentrations were increased; after 72 minutes potassium raised by 173.76% above control, calcium highest reading observed after 36 minutes (44.03% above control). 108 minutes after injection, percentage of change from control for all the ions was very close to each other (30.54%, 26.31% & 31.67% above control for sodium, potassium and calcium respectively). 144 and 180 minutes after injection, less fluctuation was observed. Neurotoxic venom of this scorpion was found to change serum concentration of three fundamental electrolytes in nervous system biochemical mechanism. In addition this change may greatly affect toxin binding to ion channels as well as homeostatic balance. We suggest that, fatal symptoms due to scorpion stings are not only limited to direct interactions of PNs with VGSCs, but also toxin-affected neuro-chemical homeostasis could affect the behaviour of VGSCs.

The diversity of bird species is expected to vary with habitat type even at the smallest spatial scales. In this paper, we describe a preliminary survey conducted for the avifauna at two locations in Khartoum city, namely, Sunut forest and Tuti Island. The ecology of both sites is influenced by their proximity to the Nile River and thus they are characterized by dense vegetation cover. Moreover, the two sites lie very close to each other, implying that the climatic conditions are virtually identical. However, the two sites differ with respect to one major environmental respect, that is, the intensity of human influence. Tuti Island represents a man-made habitat and the vegetation at the site is mainly agricultural. On the other side, Sunut forest is a natural habitat and the vegetation cover at the site is dominated by the wild Acacia nilotica trees. The goal of the study is to compare the bird composition between the two sites in order to assess the effect of habitat type on the spatial variation in the abundance and diversity of birds. Overall, forty one species were recorded at the two sites during a five-month period: twenty four species at Sunut forest and thirty species at Tuti Island. Statistical investigation of avian diversity using Shannon index has detected a significant difference between the two sites, most likely due to variable human impact.

The aim of this study was to identify the endophytic fungi of the medicinal plant Kigelia africana (Lam) Benth. (Bignoniaceae) and to investigate their potential antimicrobial activity. Seven species of endophytic fungi were successfully isolated from K. Africana for the first time: including Cladosporium sp., Aspergillus flavus, Aspergillus sp., Curvularia lunata as well as three unknown species. The fungal extracts were assessed for antibacterial activity against three standard pathogenic bacterial strains: Bacillus subtilis, Staphylococcus aureus and Escherichia coli. Most of the extracts showed in vitro inhibition of bacterial growth. The phytochemical screening revealed the existence of a diverse group of secondary metabolites in the crude extracts of the endophytic fungi that resemble those in the host plant extracts.

In theory, the selective attacks by experienced predators are expected to drive aposematic prey species towards colour monomorphism because mutant individuals with divergent colour forms will not be recognized as distasteful and thus will be targeted by predators. The tropical butterfly Danaus chrysippus represents a notable exception to this rule since it is aposematic but shows extensive colour pattern polymorphism in the region of East and Central Africa. In this paper, we present a critical review of the various hypotheses that were suggested to explain the origin and maintenance of colour polymorphism in D. chrysippus. Three different approaches to this problem were revised and criticized: first, that polymorphism is a non-adaptive consequence of past geographic isolation that resulted in the formation of a hybrid zone, second, that polymorphism represents an evolutionary escape route when an aposematic colour form is heavily loaded by batesian mimics and third, that polymorphism is maintained because D. chrysippus is subjected to spatially and temporally variable Mullerian selection as a result of recurrent population extinctions in the mimetic Acraea species, driven by the spread of the male-killing Wolbachia bacterium. It has been argued that the three hypotheses are not mutually exclusive; alternatively, each hypothesis targets a distinct problem and exploits a distinct set of key observations. The study concluded that the final solution to the long standing problem of aposematic polymorphism in D. chrysippus might be achieved through the adoption of a pluralistic approach that integrates all the three hypotheses.

Due to their scientific value as bioindicators, assessment of ant diversity is an important target of biological diversity research, especially in regions where conservation threats are substantial. In this paper, we present a preliminary investigation of the ant fauna at Sunut forest which is a natural forest located in the middle of Khartoum city, the capital of Sudan. Due to its location, the habitat at Sunut forest is increasingly threatened by human activities. Our goal is to provide a database to serve as a guide for future management and conservation research taking place at this forest. During the study period (May, June and July 2012), ten species of ants were collected and classified. The ant collection contained species with different habitat preferences, indicating that the environment at Sunut forest is highly heterogeneous.

Within a forest, the spatial variation in leaf litter composition is expected to affect both the density and diversity of leaf litter insects. In this study, a comparison of insect community structure in the leaf litter has been conducted between three habitats at Amani Nature Reserve: Bamboo shrubs (Bambuseae), gum trees (Eucalyptus sp.) and camphor trees (Cinnamomum camphora). A total number of 1919 individuals were collected from pitfall traps and 658 species from quadrate plots. Collected specimens were found to represent 8 different orders: Blattodea, Coleoptera, Collembolan, Diptera, Hemiptera, Hymenopter, Orthoptera and Thysanura. Diptera had the highest abundance in the overall collection. Statistical analysis did not detect a significant difference in insect composition between the three leaf litter habitats. Likewise, the depth of litter material had no significant influence on insect composition. Furthermore, no significant difference in insect composition was detected between day and night collections. Overall, these results suggest that the community of leaf litter insects at Amani Nature Reserve is characterized by considerable stability against spatial and temporal environmental fluctuations.

Sex ratio distortion in the tropical butterfly Acraea encedana is caused by infection with a male-killing bacterium of the genus Wolbachia. Previous research on this species has reported extreme female bias, high bacterial prevalences, and full sex role reversal. In this paper, we provide an assessment for the dynamics of the male-killer, based on a survey for sex ratios and Wolbachia prevalences among wild populations of A. encedana in Uganda. The study reveals that Wolbachia infection showed considerable variation over both spatial and temporal scales.

Al-Sunut is a natural forest located in the centre of Khartoum state, the capital of Sudan. Due to its unique location, Sunut forest is severely stressed by human activities, especially construction. In this paper, we provide a survey for the biodiversity at Sunut Forest. Three animal groups were investigated for density and species diversity: Birds, Acacia nilotica associated arthropods and ground arthropods. The aim of the study was to provide the field data required for the design of adequate management and conservation plans and to draw the popular attention to the special value of Sunut forest. The study concluded that Sunut forest hosts considerable biological diversity, particularly of birds, as 87 species were recorded. Arthropod specimens that belong to 10 different orders were collected from A. nilotica trees. Likewise, specimens of ground arthropods collected from the forest represent 11 different orders.

Within the region of East and Central Africa, the aposematic butterfly D. chrysippus is characterized by unusual ecology, due to the co-occurrence of polymorphism, mimicry and sex ratio distortion. In this paper, we describe a survey conducted for D. chrysippus at Khartoum, based upon morphological and molecular investigations. The goal of the study was to determine whether Sudan is a part of the presumed hybrid zone of D. chrysippus in Africa, where the butterfly shows the unusual ecology. D. chrysippus was found to display considerable colour pattern polymorphism. Only one mimetic form, the batesian mimic, female Hypolimnas misippus was recorded. The population sex ratio of D. chrysippus did not show significant deviation from the 1:1 ratio. Molecular tests for the male-killing bacteria Spiroplasma yielded negative results. The study concluded that central Sudan belongs to the hybrid zone but lacks its characteristic ecology.

Within certain regions in East Africa, the butterfly Danaus chrysippus (L.) shows female-biased population sex ratio, because of the production by some females of all-female broods, as a result of infection by maternally inherited, male-killing bacterium of the genus Spiroplasma. In this study, we describe a 3-year field survey for the population dynamics of the male-killing Spiroplasma in D. chrysippus in four independent localities, namely Uganda, Ghana, Sudan and Madagascar. The prevalence of the bacterium was found to show extensive variations at multiple scales among different sites, in various countries, seasons and years. A novel, selection-based hypothesis was suggested to explain the high variability of male-killer prevalence over space and time, based on the existence of an adaptive link between larval food-plant density and the magnitude of resource reallocation fitness advantage for the male-killer.

Sex ratio distortion in the tropical butterfly Acraea encedana is caused by infection with a male-killing bacterium of the genus Wolbachia. Previous research on this species has reported extreme female bias, high bacterial prevalences, and full sex role reversal. In this paper, we provide an assessment for the dynamics of the male-killer, based on a survey for sex ratios and Wolbachia prevalences among wild populations of A. encedana in Uganda. The study reveals that Wolbachia infection showed considerable variation over both spatial and temporal scales.

Female-biased sex ratios occur in many insect species as a consequence of infection by maternally-inherited male-killing bacterial endosymbionts. In this paper, we revise the research conducted on the phenomenon of male-killing in African nymphalid butterflies, with special focus on the cases of Danaus chrysippus , Acraea encedon and Acraea encedana . The evolution of male-killing in each case was addressed, together with the phylogeny of male-killers that were identified from this group. Moreover, the potential impacts that male-killers might impose on the evolution of their butterfly hosts were thoroughly investigated. In the end of this review, we present a number of unanswered questions to be targeted by future research work on the male-killing in these butterflies.