Sex allocation conflict in insect societies: who wins?

Sex allocation in colonies of eusocial Hymenoptera is one of the best studied social conflicts. We outline a framework for analysing conflict outcome through power and the costs of manipulation and suggest that the conflict will often be unresolved because both major parties of interest, the queen and the workers, should manipulate allocation even at considerable costs to the colony. We suggest future work for analysing power in the conflict between queen and workers over sex allocation and discuss the extent of male power.     

Darwin and Mendel: who was the pioneer of genetics?

Although Mendel is now widely recognized as the founder of genetics, historical studies have shown that he did not in fact propose the modern concept of paired characters linked to genes, nor did he formulate the two "Mendelian laws" in the form now given. Furthermore, Mendel was accused of falsifying his data, and Mendelism has been met with scepticism because of its failure to provide scientific explanation for evolution, to furnish a basis for the process of genetic assimilation and to explain the inheritance of acquired characters, graft hybridization and many other facts. Darwin was the first to clearly describe almost all genetical phenomena of fundamental importance, and was the first to present a developmental theory of heredity--Pangenesis, which not only greatly influenced many subsequent theories of inheritance, particularly those of de Vries, Galton, Brooks and Weismann, but also tied all aspects of variation, heredity and development together, provided a mechanism for most of the observable facts, and is supported by increasing evidence. It has also been indicated that Darwin's influence on Mendel, primarily from The Origin, is evident. The word "gene" was derived from "pangen", itself a derivative of "Pangenesis" which Darwin had coined. It seems that Darwin should have been regarded as the pioneer, if not of transmissional genetics, of developmental genetics and molecular genetics.     

Breaching the basement membrane: who, when and how?

The basement membrane (BM), a specialized network of extracellular matrix macromolecules, surrounds epithelial, endothelial, muscle, fat and nerve cells. During development, immune surveillance and disease states ranging from cancer to fibrosis, host cells penetrate the BM by engaging tissue-invasive programs, the identity of which remain largely undefined. Although it is commonly assumed that all cells employ similar mechanisms to cross BM barriers, accumulating evidence indicates that cells might selectively mobilize protease-dependent or -independent invasion programs. New data indicate that protease-dependent transmigration is largely reliant on a group of membrane-anchored metalloenzymes, termed the membrane-type matrix metalloproteinases, which irreversibly remodel BM structure. By contrast, mechanisms that enable protease-independent transmigration remain undefined and potentially involve the reversible disassembly of the BM network. Further characterization of the molecular mechanisms underlying BM transmigration should provide important insights into pathophysiologic tissue remodeling events and also enable the development of novel therapeutics.     

Virulence and resistance in malaria: who drives the outcome of the infection?

Theoretical and experimental studies have established the dynamic nature of virulence and that, like all traits, it has evolved. Understanding parasite evolution offers a conceptual framework for diverse fields and can contribute greatly to decision-making in disease control. Recently, Grech et al. investigated the effects of host genotype-by-parasite genotype interactions on the expression of virulence in an artificial rodent-malaria system. They found that both parasite and host effects explained most of the variance in the virulence, resistance and transmission potential. These findings are a major contribution to the emerging debate on the pros and cons of a coevolutionary approach of virulence evolution; they also hold great potential for more effective control strategies.     

Schistosome monogamy: who,how, and why?

Schistosomes represent a unique animal model for comparative analyses of monogamy. Indeed, schistosomes are classified at the lowest taxonomical level of monogamous species and lack complex social interactions, which could alter our understanding of their unusual mating system. Elements discussed here include the fact that monogamy in schistosomes could be an ancestral state between hermaphroditism and polygyny or polygynandry and the occurrence of mate changes. In addition, hypotheses are proposed to explain monogamy in schistosomes (e.g. female dispersion, the need for paternal care, oviposition site limitation or aggressiveness, and mate guarding). We also propose future experimental and analytical approaches to improve our understanding of the schistosomes' mating system.     

Speciation: don't fly and diversify?

Loss of flight in Japanese carrion beetles is correlated with greater population subdivision and higher speciation rate. This reveals the complex relationship of trait evolution with dispersal power, range size and diversification.     

Restriction-modification systems and bacteriophage invasion: Who wins?

The success of a phage that infects a bacterial cell possessing a restriction-modification (R-M) system depends on the activities of the host methyltransferase and restriction endonuclease, and the number of susceptible sites in the phage genome. However, there is no model describing this dependency and linking it to observable parameters such as the fraction of surviving cells under excess phage, or probability of plating at low amount of phages. We model the phage infection of a cell with a R-M system as a pure birth process with a killing state. We calculate the transitional probabilities and the stationary distribution for this process. We generalize the model developed for a single cell to the case of multiple identical cells invaded by a Poisson-distributed number of phages. The R-M enzyme activities are assumed to be constant, time-dependent, or random. The obtained results are used to estimate the ratio of the methyltransferase and endonuclease activities from the observed fraction of surviving cells.     

The Lengthening of a Giant Protein: When, How, and Why?

Subcommissural organ (SCO)-spondin is a giant glycoprotein of more than 5000 amino acids found in Vertebrata, expressed in the central nervous system and constitutive of Reissner’s fiber. For the first time, in situ hybridization performed on zebrafish (Danio rerio) embryos shows that the gene encoding this protein is expressed transitionally in the floor plate, the ventral midline of the neural tube, and later in the diencephalic third ventricle roof, the SCO. The modular organization of the protein in Echinodermata (Strongylocentrotus purpuratus), Urochordata (Ciona savignyi and C. intestinalis), and Vertebrata (Teleostei, Amphibia, Aves and Mammalia) is also described. As the thrombospondin type 1 repeat motifs represent an increasingly large part of the protein during Deuterostomia evolution, the duplication mechanisms leading to this complex organization are examined. The functional significance of the particularly well-preserved arrangement of the series of SCO-spondin repeat motifs and thombospondin type 1 repeats is discussed. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Neuronal variability: noise or part of the signal?

Sensory, motor and cortical neurons fire impulses or spikes at a regular, but slowly declining, rate in response to a constant current stimulus. Yet, the intervals between spikes often vary randomly during behaviour. Is this variation an unavoidable effect of generating spikes by sensory or synaptic processes ('neural noise') or is it an important part of the 'signal' that is transmitted to other neurons? Here, we mainly discuss this question in relation to sensory and motor processes, as the signals are best identified in such systems, although we also touch on central processes.