Venomics survey of six myrmicine ants provides insights into the molecular and structural diversity of their peptide toxins.

Among ants, Myrmicinae represents the most speciose subfamily. The venom composition previously described for these social insects is extremely variable, with alkaloids predominant in some genera while, conversely, proteomics studies have revealed that some myrmicine ant venoms are peptide-rich. Using integrated transcriptomic and proteomic approaches, we characterized the venom peptidomes of six ants belonging to the different tribes of Myrmicinae. We identified a total of 79 myrmicitoxins precursors which can be classified into 38 peptide families according to their mature sequences. Myrmicine ant venom peptidomes showed heterogeneous compositions, with linear and disulfide-bonded monomers as well as dimeric toxins. Several peptide families were exclusive to a single venom whereas some were retrieved in multiple species. A hierarchical clustering analysis of precursor signal sequences led us to divide the myrmicitoxins precursors into eight families, including some that have already been described in other aculeate hymenoptera such as secapin-like peptides and voltage-gated sodium channel (NaV) toxins. Evolutionary and structural analyses of two representatives of these families highlighted variation and conserved patterns that might be crucial to explain myrmicine venom peptide functional adaptations to biological targets.

Description of Heteracris lecoqi Yetchom-Fondjo amp; Kekeunou sp. nov. and Heteracris hannai Wandji amp; Kekeunou sp. nov. and redescription of Heteracris guineensis (Krauss, 1890) (Orthoptera: Acrididae) with comments on its ecology in the Southern part of Cameroon.

The specimens studied were collected with sweep net and pitfall in the forests, agro-forests, herbaceous fallows, and crop fields of 14 localities in the southern part of Cameroon, from August 2015 to February 2018. The results show that Heteracris hannai sp. nov. and Heteracris lecoqi sp. nov. differ from previously known species of the same genus by the pattern of coloration and the details or shape of the phallic complex. H. lecoqi sp. nov. is characterized by light brownish body; male cercus with flattened, downcurved and obtuse apex; lophus strongly curved; interlophal space with V shape; apodeme of cingulum bow, convergent, with V-shape; valve of cingulum in lateral view longer than apical valve of penis; ramus in ventral view joined. H. hannai sp. nov. is distinct to other species by brown to grey body; male cercus with apex rounded, curved inside; lophus curved; interlophal space with U-shape; apodeme of cingulum thick, slightly parallel, with U shape; valve of cingulum in lateral view hardly longer than apical valve of penis; ramus in ventral view opened. The characteristics of H. guineensis are closer to H. hannai sp. nov. than to H. lecoqi sp. nov. H. lecoqi sp. nov. was collected only in the fallows while H. hannai sp. nov. was collected in the forests, agro-forests, fallows, and crop fields. Compared to H. guineensis, both new species are scarce in the natural vegetation and their distribution area is limited to two and four localities respectively for H. lecoqi sp. nov. and H. hannai sp. nov. All these three grasshopper's species were recorded as accidental species in all types of vegetation.

The Peptide Venom Composition of the Fierce Stinging Ant Tetraponera aethiops (Formicidae: Pseudomyrmecinae).

In the mutualisms involving certain pseudomyrmicine ants and different myrmecophytes (i.e., plants sheltering colonies of specialized "plant-ant" species in hollow structures), the ant venom contributes to the host plant biotic defenses by inducing the rapid paralysis of defoliating insects and causing intense pain to browsing mammals. Using integrated transcriptomic and proteomic approaches, we identified the venom peptidome of the plant-ant Tetraponera aethiops (Pseudomyrmecinae). The transcriptomic analysis of its venom glands revealed that 40% of the expressed contigs encoded only seven peptide precursors related to the ant venom peptides from the A-superfamily. Among the 12 peptide masses detected by liquid chromatography-mass spectrometry (LC-MS), nine mature peptide sequences were characterized and confirmed through proteomic analysis. These venom peptides, called pseudomyrmecitoxins (PSDTX), share amino acid sequence identities with myrmeciitoxins known for their dual offensive and defensive functions on both insects and mammals. Furthermore, we demonstrated through reduction/alkylation of the crude venom that four PSDTXs were homo- and heterodimeric. Thus, we provide the first insights into the defensive venom composition of the ant genus Tetraponera indicative of a streamlined peptidome.

A Checklist of Short-horned Grasshopper Species (Orthoptera: Caelifera) from Littoral Region of Cameroon with description of a new species of the genus Hemierianthus Saussure, 1903 (Orthoptera: Chorotypidae).

The Littoral Region of Cameroon is one of the most highly disturbed regions in Cameroon that remain poorly studied and where no investigation regarding the grasshopper fauna has been conducted. Hence a survey was conducted from August 2015 to November 2018 in 11 localities of this region. In each locality, grasshoppers were sampled in three vegetation types (forests, fallows and cultivated farms) using sweep nets sampling method. We collected in total 51 short-horned grasshopper species belonging to the families Acrididae, Chorotypidae, Euschmidtiidae, Pyrgomorphidae and Thericleidae. Among these species, 43 belong to Acrididae, 5 to Pyrgomorphidae and only one belongs to the Chorotypidae, Euschmidtiidae and Thericleidae respectively. The Chorotypidae species Hemierianthus mbongueensis Yetchom Xu sp.nov. is also described in this study. Twelve grasshopper species were widely distributed as they occurred in all study sites and 11 were recorded exclusively from one study site. This study showed that there is high species richness of short-horned grasshoppers in the Littoral Region of Cameroon. However, more sampling effort in different ecosystems of this region and other regions of Cameroon will certainly improve our understanding on grasshopper taxonomy, ecology and biogeography.

Melissotarsus ants are likely able to digest plant polysaccharides.

Melissotarsus ants have an extremely specialized set of behaviours. Both workers and gynes tunnel galleries in their host tree bark. Workers walk with their mesothoracic legs pointing upwards and tend Diaspididae hemiptera for their flesh. The ants use their forelegs to plug the galleries with silk that they secrete themselves. We hypothesised that the ants' energetic needs for nearly constant gallery digging could be satisfied through the absorption of host tree tissues; so, using basic techniques, we examined the digestive capacities of workers from two species. We show that workers are able to degrade oligosaccharides and heterosides as well as, to a lesser degree, polysaccharides. This is one of the rare reports on ants able to digest plant polysaccharides other than starch.

Thermotolerance adaptation to human-modified habitats occurs in the native range of the invasive ant Wasmannia auropunctata before long-distance dispersal.

Key evolutionary events associated with invasion success are traditionally thought to occur in the introduced, rather than the native range of species. In the invasive ant Wasmannia auropunctata, however, a shift in reproductive system has been demonstrated within the native range, from the sexual non-dominant populations of natural habitats to the clonal dominant populations of human-modified habitats. Because abiotic conditions of human- modified habitats are hotter and dryer, we performed lab experiments on workers from a set of native and introduced populations, to investigate whether these ecological and genetic transitions were accompanied by a change in thermotolerance and whether such changes occurred before establishment in the introduced range. Thermotolerance levels were higher in native populations from human-modified habitats than in native populations from natural habitats, but were similar in native and introduced populations from human-modified habitats. Differences in thermotolerance could not be accounted for by differences in body size. A scenario based on local adaptation in the native range before introduction in remote areas represents the most parsimonious hypothesis to account for the observed phenotypic pattern. These findings highlight the importance of human land use in explaining major contemporary evolutionary changes.

Genetic structure, nestmate recognition and behaviour of two cryptic species of the invasive big-headed ant Pheidole megacephala.

BACKGROUND: Biological invasions are recognized as a major cause of biodiversity decline and have considerable impact on the economy and human health. The African big-headed ant Pheidole megacephala is considered one of the world's most harmful invasive species. METHODOLOGY/PRINCIPAL FINDINGS: To better understand its ecological and demographic features, we combined behavioural (aggression tests), chemical (quantitative and qualitative analyses of cuticular lipids) and genetic (mitochondrial divergence and polymorphism of DNA microsatellite markers) data obtained for eight populations in Cameroon. Molecular data revealed two cryptic species of P. megacephala, one inhabiting urban areas and the other rainforests. Urban populations belong to the same phylogenetic group than those introduced in Australia and in other parts of the world. Behavioural analyses show that the eight populations sampled make up four mutually aggressive supercolonies. The maximum distance between nests from the same supercolony was 49 km and the closest distance between two nests belonging to two different supercolonies was 46 m. The genetic data and chemical analyses confirmed the behavioural tests as all of the nests were correctly assigned to their supercolony. Genetic diversity appears significantly greater in Africa than in introduced populations in Australia; by contrast, urban and Australian populations are characterized by a higher chemical diversity than rainforest ones. CONCLUSIONS/SIGNIFICANCE: Overall, our study shows that populations of P. megacephala in Cameroon adopt a unicolonial social structure, like invasive populations in Australia. However, the size of the supercolonies appears several orders of magnitude smaller in Africa. This implies competition between African supercolonies and explains why they persist over evolutionary time scales.

Initial behavior in colony fragments of an introduced population of the invasive ant Wasmannia auropunctata.

We investigated in the laboratory the initial behavior of propagules of the invasive ant Wasmannia auropunctata in Cameroon where it has been introduced. Both workers and queens at first feigned death (thanatosis), and then the workers slowly moved around the experimental arena; the queens did the same about 10seconds later. Each queen antennated selected workers that then aggregated together by grasping the hind leg of another ant with their mandibles. When encountering the queen again, the lead worker climbed up the queen's hind leg and onto her back, followed by some other individuals. The remaining workers followed the queen to a location in the experimental arena. When brood was present, the workers transferred it to this location. Orphaned workers did not aggregate, but gathered the brood together and took care of it. By permitting propagules to survive, these behaviors likely contribute to the success of W. auropunctata as an invader.

The raiding success of Pheidole megacephala on other ants in both its native and introduced ranges.

We studied the behaviour of the invasive African myrmicine ant, Pheidole megacephala, when confronted with colonies of other common ant species in Cameroon, a part of its native range, and in Mexico, where it has been introduced. P. megacephala raided the nests of the other ants in both cases. Eleven species out of 12 put up a rather strong resistance to raiding P. megacephala workers in Cameroon compared to only three species out of 11 in Mexico, where only colonies of Solenopsis geminata, Dorymyrmex pyramicus and Dolichoderus bispinosus resisted these raids. We conclude that P. megacephala's heightened ability to successfully raid colonies of competing ants may help explain its success and the decline of native ants in areas where it has been introduced.

The predatory behavior of Pheidole megacephala.

We studied the foraging and predatory behaviors of the invasive African myrmicine ant, Pheidole megacephala (F.) in its native range. Workers can singly capture a wide range of insects, including relatively large prey items. For still larger prey, they recruit at short range those nestmates situated within reach of an alarm pheromone and together spread-eagle the insect. These behaviors are complimented by a long-range recruitment (of nestmates remaining in the nest) based on prey size. P. megacephala scouts also use long-range recruitment when they detect the landmarks of termites and competing ant species, thus permitting them to avoid confronting these termites and ants solitarily.

The predatory behaviour of a tramp ant species in its native range.

Workers of the pest ant Paratrechina longicornis participate in a type of group hunting. Each individual forages with its long antennae wide open and moves quickly (6.3 cm/s) along an erratic path surrounded by nestmates behaving in the same way and within range of a recruiting pheromone. They detect prey by contact with successful workers singly capturing and retrieving small prey and seizing larger ones by an appendage. Then they recruit nestmates at short-range; all together they spread-eagle the prey and retrieve them whole.

Serum concentration of vitamins A and E and lipid in a rural population of north Cameroon.

BACKGROUND: Vitamin A deficiency is still a major health problem mostly affecting people in developing countries. It contributes to increased mortality and morbidity through current infection. In Cameroon, it is a public health problem mostly in the northern part where palm oil, which is a principal source of provitamin A in the south of the country, is not consumed. AIM: We carried out this research to discover the relationship between vitamins (A and E) and blood lipids in a normal rural population living in vitamin A-deficiency area. DESIGN: A cross-sectional study with 81 healthy volunteers (40 men and 41 women) aged 3-61 (mean 18.32 +/- 1.63) years and living in two neighboring villages (Doyan and Larao) in the northern part of Cameroon, where previous studies revealed a prevalence of vitamin A deficiency of 33.3%. METHODS: Serum concentrations of vitamins A and E were measured by fluorometric methods. Serum cholesterol and lipids were assayed by enzymatic methods. RESULTS: The mean +/- standard error for vitamin A and E were 15.09 +/- 0.82; 526.99 +/- 29.57 mug/100 ml, respectively. The concentrations of the serum parameters analyzed were similar for both sexes, whereas the atherogenic ration of cholesterol (ARC) was significantly (p < 0.036) higher in women. Serum lipids (total lipids, total cholesterol, low-density lipoprotein and phospholipids) correlated with vitamins A and E (p < 0.05). Vitamins A and E were highly correlated with each other (r = 0.42, p < 0.001). Age was positively associated with vitamin A (r = 0.42, p < 0.001) and vitamin E (r = 0.29, p < 0.01). Deficiency of vitamins A and E constitutes a public health problem with more than 56% of the subjects having low levels of these vitamins, while subjects tested had a low risk for cardiovascular diseases. CONCLUSION: In this population we noticed normal lipid levels and vitamin A deficiency probably resulting from diets poor in provitamin A.