Sweaty skin: an invitation to bite?

Anopheles gambiae sensu stricto and Aedes aegypti have a preference for human blood, which determines their importance as vectors of pathogens responsible for human diseases. Volatile organic chemicals are the principal cues by which humans are being located. Human sweat contains components that are attractive to anthropophilic mosquito species, and variation in sweat composition causes differential attractiveness to mosquitoes within and between individuals and also between humans and other mammals. Characteristics of skin glands and skin microbiota define the odorous organic compounds emitted by sweat, thereby the degree of attractiveness of the host to mosquitoes. Carboxylic acids in particular appear to characterize humans. Thus sweat-associated human volatiles are probably the primary determinant factor in the host preference of anthropophilic mosquitoes.     

Centrosomes: Central no more?

It has recently been found that the zygotic development of a morphologically normal fly can occur without properly functioning mitotic centrosomes. Does this mean that centrosomes are not required for cell division in animals at all?     

Cranial morphology and bite force in Chamaeleolis lizards--adaptations to molluscivory?

Anolis lizards have become a model system for the study of adaptive radiations as species with similar morphologies occupying similar habitats have arisen independently on all the larger islands in the Caribbean. However, on both, Cuba and Hispaniola unique forms have evolved that seemingly have no counterparts on any of the other Caribbean islands. Anoles of the genus Chamaeleolis comprise such a unique form and have been termed 'twig giants' because of their cryptic life style, slow locomotor mode, and short limbs. However, some of the most unusual features of these lizards are their large heads and molluscivorous diet. Here, we compare head shape, bite force, and muscle structure among sexes and age classes of Chamaeleolis lizards with Anolis crown giants. Our data show that Chamaeleolis lizards have a dramatically different head shape characterized by tall heads with a pronounced temporal ridge and long snouts. Analyses of bite force, surprisingly, show no differences between adult Chamaeleolis and Anolis crown giants. Juveniles of Chamaeleolis, however, have very tall heads for their size and bite harder than Anolis juveniles do. This can be related to the propensity of juveniles of this genus to eat snails, food items for which high bite forces are crucial. This observation is corroborated by the presence of well-developed jaw adductors in juveniles. Thus, our data suggest that the unusual phenotype of adults with large and tall heads may be due to selection on the juvenile life history stages.     

Personal genomes: no bad news?

Issues in genetics and genomics have been centre stage in Bioethics for much of its history, and have given rise to both negative and positive imagined futures. Ten years after the completion of the Human Genome Project, it is a good time to assess developments. The promise of whole genome sequencing of individuals requires reflection on personalization, genetic determinism, and privacy.     

The spliceosome: no assembly required?

In this issue of Molecular Cell, Stevens et al. purify a large particle from yeast extracts that contains all five of the U snRNPs required for pre-mRNA splicing. The existence of this "penta-snRNP" suggests the provocative possibility that spliceosome assembly does not depend upon a pre-mRNA substrate.     

Built to bite? Differences in cranial morphology and bite performance between narrow‐ and broad‐headed European glass eels

The presence of two phenotypes in a single species is a widespread phenomenon, also observed in European eel (Anguilla anguilla). This dimorphism has been related to dietary differences in the subadult elver and yellow eel stages, with broad‐heads generally feeding on harder and/or larger‐bodied prey items than narrow‐heads. Nevertheless, both broad‐ and narrow‐headed phenotypes can already be found among glass eels, the stage preceding the elver eel stage. As these glass eels are considered nonfeeding, we investigate here to what degree the observed variation in head width is reflected in variation in the musculoskeletal feeding system, as well as whether this reflects the same variation observed in the older, dimorphic yellow eels. Additionally, we investigate whether musculoskeletal differences between broad‐ and narrow‐headed glass eels have implications on their feeding performance and could thus impact prey preference when eels start feeding. Therefore, we compared the cranial musculoskeletal system of five broad‐ and narrow‐headed glass eels using 3D‐reconstructions and simulated the glass eel's bite force using the data of the muscle reconstructions. We found that the variation in the musculoskeletal system of glass eels indeed reflects that of the yellow eels. Broader heads were related to larger jaw muscles, responsible for mouth closure. Accordingly, broad‐heads could generate higher bite forces than narrow‐headed glass eels. In addition, broader heads were associated with higher coronoid processes and shorter hyomandibulae, beneficial for dealing with higher mechanical loadings and consequently, harder prey. We, thus, show that head width variation in glass eels is related to musculoskeletal differences which, in turn, can affect feeding performance. As such, differences in prey preference can already take place the moment the eels start feeding, potentially leading to the dimorphism observed in the elver and yellow eel stage.     

Trunk spines of trees: a physical defence against bark removal and climbing by mammals?

Background and Aims The defensive role of spines has previously been related to leaves, young shoots and reproductive organs. However, some woody species harbour spines on their trunks where none of those organs are present. Several explanations are plausible: they could be (1) climbing aids, (2) remnants from defence of leaves or reproductive organs during an earlier development phase, or (3) an as-yet undescribed defence. Here we investigate whether they could play a role against either bark feeding or preventing climbing animals accessing food resources in the tree canopy.MethodsWe described 31 woody species with spines on their trunk, growing in a botanical garden, to test whether morphological strategies could be identified and suggest what could be their most likely function. As testing their function is difficult experimentally for large pools of species, we performed virtual experiments to evaluate the potential roles of trunk spines against bark removal and climbing animals of different sizes. We then compared for each species and their confamilial non-spiny species the nutritional profiles of leaf, bark and reproductive organs to test whether trunk spines were associated with a nutritious organ (more likely targeted by herbivores).Key ResultsWe identified four morphological syndromes of trunk spines. Two corresponded to already known functions (anchorage for lianas and crown defence against large ground mammals), and two strategies are newly described trait syndromes with traits suggesting a defence against bark feeding and climbing mammals. By simulation, we show how each strategy could translate into defence against debarking and prevent herbivores from climbing.ConclusionsWe identified trunk spine strategies and the criteria to classify them, their most likely function and the likely feeding mode and size of animal against which different trunk spine strategies may be effective. We discuss further perspectives for testing their function and their ecological significance.     

Predicting the unpredictable: How host specific is the mycobiota of bark and ambrosia beetles?

Bark and ambrosia beetles (Curculionidae: Scolytinae) are known for their symbioses with fungi and play a key role in the dispersal of phytopathogens. The scolytine community of eight pine stands along a latitudinal gradient in the UK was surveyed and beetle-associated fungal communities (mycobiota) were assessed using ITS2 metabarcoding (304 specimens, 12 species). Distribution patterns among 2,257 detected fungal Operational Taxonomic Units (OTUs) revealed that beetle species identity was an important predictor of mycobiotic richness and composition, while the effects of environmental and spatial variables were negligible. Network-based specificity analysis suggested that a relatively small subset of OTUs (75 in total) exhibit an affinity for a subset of beetle species and that these include many Microascales and Saccharomycetes. Notably though, of the OTUs belonging to the family Ophiostomataceae, relatively few display host specificity. Our results add to the complex picture of host-associated fungal communities and suggest that host range limits are unlikely to restrict the spread of economically important phytopathogens.     

Chronic bee paralysis: A disease and a virus like no other?

Chronic bee paralysis which was called Paralysis is a rather unusual disease caused by a rather unusual virus. In this review, we explore current knowledge of the disease and its etiological agent. Paralysis is the only common viral disease of adult bees whose symptoms include both behavioural and physiological modifications: trembling and hair loss. The disease often affects the strong colonies of an apiary and thousands of dead individuals are then observed in front of the hives. Two sets of symptoms have traditionally been described in the existing literature, but nowadays we can define a general syndrome.The morphology of the Chronic bee paralysis virus (CBPV) particles and the multipartite organisation of the RNA genome are exceptional, as most honey bee viruses are picorna-like viruses belonging to the Iflavirus and Cripavirus genera with symmetric particles and monopartite positive, single-strand RNA genomes. CBPV is currently classified as an RNA virus but is not included in any family or genus. Although it shares several characteristics with viruses in the Nodaviridae and Tombusviridae families, it differs from previously known viruses according to the various demarcation criteria defined by the International Committee on Taxonomy of Viruses (ICTV). Thus, it should be considered as the type species of a new group of positive-strand RNA viruses.The recent sequencing of the complete CBPV genome has opened the way for phylogenetic studies and development of new molecular tools able to detect variable isolates and to quantify genomic loads. This article considers the results of such recent detection tests but also previous studies including: (i) the distribution of CBPV infection within the bees and the hive, (ii) the way the virus spreads and its persistence in the colony environment, and (iii) geographical and seasonal distribution and impact of CBPV infections.     

Morphology,ornaments and performance in two chameleon ecomorphs: is the casque bigger than the bite?

The evolution of ecomorphs within a species may represent either unique evolutionary events or multiple convergent events in similar environments. Functional studies of differing morphological traits of ecomorphs have been important to elucidate their role in adaptive radiations. The Cape dwarf chameleon, Bradypodion pumilum, has two ecomorphs: a large, brightly colored, ornate form found in closed habitats, and a small, dull form with reduced ornamentation found in open vegetation. The typical form is known to use casque size to communicate fighting ability, but it is unknown whether this is an honest signal and whether casque size is related to bite force. We show through a population genetic analysis that these ecomorphs are not separate genetic lineages but the result of multiple transitions between closed and open habitats. From measurements of ornamental and non-ornamental morphological characters and bite force in 105 chameleons, we find that bite force is significantly related to head size and is best predicted by head width. Bite force was reasonably predicted by casque height in ecomorphs from closed habitats, but not in those from open habitats. For size-adjusted data, open habitat males had wider heads, biting harder than closed habitat males. Our data suggest honesty in signaling for closed habitat ecomorphs, but for open habitat ecomorphs communication is different, a finding commensurate with the common framework for species radiations.     

Do hemoglobin and hemocyanin impair schistosoma killing by no?

Nitric oxide (NO) possesses antiparasitic effects on both Protozoa and Metazoa in definitive and intermediate hosts as well as in vectors. Here, we postulate that hemoglobin and hemocyanin may impair Schistosoma killing by NO in the definitive and intermediate hosts. Interestingly, hemoglobin, myoglobin, and neuroglobin may protect Plasmodium and Trypanosoma from the antiparasitic effects of NO.     

Methylation of adenovirus genes in transformed cells and in vitro: influence on the regulation of gene expression?

An inverse correlation has been described between the levels of DNA methylation in specific segments of adenovirus DNA integrated into the genomes of transformed and tumor cells and the extent to which these segments are expressed as messenger RNA. In the adenovirus type 2 (Ad2)-transformed hamster cell lines HE2 and HE3, the virus-specific DNA binding protein (DBP) is not expressed, and the DNA in the DBP gene is completely methylated in all 5'-CCGG-3' sites. At least part of the late promoter/leader sequence of the DBP gene is present in cell lines HE2 and HE3. In line HE1, on the other hand, the DBP is expressed, and the DNA in the DBP gene is unmethylated at the 5'-CCGG-3' (HpaII) sites. The late promotor/leader sequence of the DBP gene is expressed in cytoplasmic RNA isolated from line HE1. The effect of DNA methylation has also been tested in vitro in a microinjection system using Xenopus laevis oocytes. Unmethylated DNA fragments of Ad2 (E2a region) have been found to serve as active templates. When the same fragments are methylated at the 5'-CCGG-3' sites by the HpaII DNA-methyltransferase, viral RNA synthesis is inhibited upon microinjection into oocyte nuclei. These results provide direct evidence for the notion that DNA methylated at highly specific sites is somehow involved in the regulation of gene expression.