Genetic Prediction: What are the Limits?

The spectre of determinism stalks many of the concerns surrounding the impact of genetic research into both disease and normal behaviour. The ability accurately to predict a person's actions would certainly have profound implications for notions of individuality and free will. But to what extent will the current explosion in genetic research provide more accurate predictors than have been available for millennia in the form of wealth, social status and perceived family resemblance? The genetic research program is at too early a stage to answer this question with confidence, but various indicators tend to point in the same direction: the predictive ability of genetic analysis will generally be low. This conclusion runs counter to widely perceived popular notions. The deconstruction of genetic determinism is an essential safeguard against the real concern that genetic information may be used for discrimination by unscrupulous powers.     

Fish-induced life-history shifts in the cladocerans Daphnia and Simocephalus: are they positive or negative responses?

The cladocerans Daphnia and Simocephalus were exposed to fishsmells under different food conditions, and their life-historyparameters were analysed. They showed similar responses to fishsmells and food shortage: lowered juvenile growth rate, reducedmature size, elongated maturation time, reduced brood size andincreased offspring size. The life-history changes induced bythe fish smell might be a result of deleterious effects of thefactor. Although it has been considered that fish-induced life-historyshifts in Daphnia are positive responses to predators, our resultssuggest that they are negative responses of animals that showsome other positive responses to fish, such as behavioural andmorphological changes to reduce mortality due to predation.Synergism was detected in the effects of the fish smell andfood deficiency, which suggests that fish smell reduces thetolerance of Daphnia to an environmental stress, food shortage.     

trans-Fatty acids and radical stress: What are the real culprits?

Free radical-catalysed cis-trans isomerization of unsaturated lipids in biomimetic models and their significance in eukaryotic cells have been explored in the last few years, an integrating hypothesis being that trans-fatty acids have their origins in both dietary sources and from isomerization of natural isomers by an endogenous radical stress. In this perspective, a summary of the achievements and a discussion of the possible biological sources of isomerizing radical species are given, indicating a need for further research on thiyl radical generation in biological systems. In this context, crucial questions remain to be answered by free radical research involving membrane lipids, thus contributing to lipidomics and embracing biology and medicine.     

Scaling nitrogen and carbon interactions: what are the consequences of biological buffering?

Understanding the consequences of elevated CO₂ (eCO₂; 800 ppm) on terrestrial ecosystems is a central theme in global change biology, but relatively little is known about how altered plant C and N metabolism influences higher levels of biological organization. Here, we investigate the consequences of C and N interactions by genetically modifying the N-assimilation pathway in Arabidopsis and initiating growth chamber and mesocosm competition studies at current CO₂ (cCO₂; 400 ppm) and eCO₂ over multiple generations. Using a suite of ecological, physiological, and molecular genomic tools, we show that a single-gene mutant of a key enzyme (nia2) elicited a highly orchestrated buffering response starting with a fivefold increase in the expression of a gene paralog (nia1) and a 63% increase in the expression of gene network module enriched for N-assimilation genes. The genetic perturbation reduced amino acids, protein, and TCA-cycle intermediate concentrations in the nia2 mutant compared to the wild-type, while eCO₂ mainly increased carbohydrate concentrations. The mutant had reduced net photosynthetic rates due to a 27% decrease in carboxylation capacity and an 18% decrease in electron transport rates. The expression of these buffering mechanisms resulted in a penalty that negatively correlated with fitness and population dynamics yet showed only minor alterations in our estimates of population function, including total per unit area biomass, ground cover, and leaf area index. This study provides insight into the consequences of buffering mechanisms that occur post-genetic perturbations in the N pathway and the associated outcomes these buffering systems have on plant populations relative to eCO₂.     

Ectoparasites: are they the proximate cause of cleaning interactions?

We tested the importance of ectoparasites in cleaning symbioses by comparing the activity of Caribbean cleaning gobies ( Elacatinus evelynae ) and of their clients during three daily periods (early morning, midday and late afternoon) in which ectoparasite availability varied naturally. Emergence from the benthos of gnathiid isopod larvae, the main target of cleaning goby predation, was higher at night, when cleaners are inactive, than during the day. Overall ectoparasite loads also tended to be higher on clients in the morning. This coincided with higher rates of visits to cleaning stations by client fish in the morning than at midday, but high rates of client visits were also recorded in the late afternoon. Clients were more likely to adopt stereotypical incitation poses, which increase the likelihood of being cleaned, in the morning than later in the day. Inspection bouts by cleaning gobies were longest in the morning. Cleaner and client behaviours therefore change predictably in response to natural diurnal variation in ectoparasite availability. These results add to a growing number of studies supporting the idea that cleaning symbioses are mutualisms dependent on ectoparasite removal.     

Coral and fish distribution patterns in Mafia Island Marine Park, Tanzania: fish–habitat interactions

We examined coral reef communities at 11 sites within Mafia Island Marine Park using a point count method for substrate and visually censused belt transects for fish populations. Multivariate ordinations showed that the benthic habitat differed among reefs. The patterns were mainly attributed to variations in depth, hydrodynamics and benthic composition. In total, the substratum was dominated by dead coral (49%) and algae (25%), with a live coral cover of only 14%. Three hundred and ninety-four fish species belonging to 56 families were recorded. According to MDS-ordinations and RELATE procedures, fish assemblage composition varied among sites in concordance with the habitats provided. Sites with highest proportion of dead coral exhibited highest degree of dispersion in the multivariate ordinations of fish assemblages. Stepwise multiple regression was used to determine the proportion of variance among sites which could be explained by depth, exposure, rugosity, substrate diversity, branching substrate, live coral cover, dead coral cover and different types of algae. The results showed that habitat variables explained up to 92% of the variation in species numbers and in total, and taxon-specific, abundance. Live coral cover was the foremost predictor of both numerical and species abundance, as well as of corallivores, invertivores, planktivores and of the families Pomacentridae, Chaetodontidae and Pomacanthidae. Our results suggest that habitat characteristics play a dominant role in determining fish assemblage composition on coral reefs.     

Diversification of Escherichia coli genomes: are bacteriophages the major contributors?

Determination of the genome sequence of enterohemorrhagic Escherichia coli O157 Sakai and genomic comparison with the laboratory strain K-12 has revealed that the two strains share a highly conserved 4.1-Mb sequence and that each also contains a large amount of strain-specific sequence. The analysis also revealed the presence of a surprisingly large number of prophages in O157, most of which are lambda-like phages that resemble each other. Based on these results, we discuss how the E. coli strains have diverged from a common ancestral strain, and how bacteriophages contributed to this process. We also describe possible mechanisms by which O157 acquired many closely related phages, and raise the possibility that such bacteria might function as 'phage factories', releasing a variety of chimeric or mosaic phages into the environment.     

What are the respective host and parasite contributions to toxoplasmosis?

The toxoplasmosis pathogenesis mechanism is complex because parasite and host specificities are interrelated. Advances in fundamental research (including strain genotyping, analyzing the progeny from crosses of different strains and exploring the implication of epigenetic effects on the parasite) have contributed greatly to our current knowledge of this mechanism. At the same time new data on the clinical characteristics of the disease have come to light. For example, highly virulent strains have been isolated recently in immunocompetent patients, and some studies suggest that toxoplasmosis also might be implicated in brain disorders. These recent tools and discoveries are likely to cast new light on the pathogenicity of Toxoplasma parasites and provide the key to understanding this unique form of parasitism.     

What are the relations between mechanics, gait parameters, and energetics in terrestrial locomotion?

Are the different energy-conserving mechanics (i.e., pendulum and spring) used in different gaits reflected in differences in energetics and/or stride parameters? The analysis included published data from several species and new data from horses. When changing from pendulum to spring mechanics, there is a change in the slope of metabolic rate (MR) vs. speed in all species, in birds and quadrupeds there is no step increase, and in humans there are conflicting reports. At the trot-gallop transition, where quadrupeds are hypothesized to change from spring mechanics to some combination of spring and pendulum mechanics, there is a change in slope of MR vs. speed in horses but not in other species. Stride frequency (SF) is a logarithmic function of walking speed in all species, a linear function of trotting/running speed, and nearly independent of speed in galloping. In humans and horses there is a discontinuity in SF at the walk-trot (run) transition but not in birds. The slope of time of contact vs. speed does not change with mechanics in most species, but it does in humans. In horses and humans, there is a discontinuity at the walk-trot (run) transition and data for other species do not permit generalization. Duty factor (DF) in humans is greater than 0.5 in walking (pendulum mechanics) and less than 0.5 when running (spring mechanics). However, this is not true in many species that have DF>0.5 at the lowest speeds where they use spring mechanics. When trotting at low speeds, horses use forelimb DF>0.5 and hind limb DF<0.5. Thus, it is confusing to distinguish between walking and running by DF.     

Fusion of vacuoles--where are the membranes, and where are the holes?

In the February 8th issue of Cell, Wang et al. report the surprising finding that vacuolar fusion occurs at the periphery of the contact area of the vacuoles and not by the expansion of a central fusion pore. During fusion, a disk of boundary membrane is excised and left behind within the fused vacuoles.     

Wildflower-pollinator interactions: Which phytochemicals are involved?

The intensification of agricultural practices contributes to the decline of many taxa, such as insects and weeds. Wildflower species have an important environmental impact on rural biodiversity since plant-pollinator networks play a key role in both landscape aesthetics and environmental functionality. Due to their scarcity and/or disappearance in conventional agroecosystems, wildflowers are now being used in strips to restore the agro-environment.In this study, fifteen wildflower species were sown in order to verify their ecological performance in terms of a plant-pollinator interaction while in laboratory the several chemicals emitted by the flowers were identified. Flowering periods were concentrated in the spring, although flowering periods extended to the hot and dry summer months in some species. An extreme variability was found in terms of quantitative and qualitative pollinator-attractiveness (i.e., bees, bumblebees, hoverfly, bee flies and butterflies). Most wildflower species emit a volatiles belonging above all to one of the several chemical classes. A hierarchical cluster analysis of the different volatile emissions did not fully correlate with the botanical taxa of the respectives wildflowers. Often, single chemical compounds prevailed, such as β-ocimene and limonene among monoterpenes hydrocarbons, santolina alcohol in the case of oxygenated monoterpenes, or (Z)- or (E)-3-hexenol acetate for non-terpenes derivatives. It is believed that these chemical compounds can play an ecological role in plant-pollinator food webs. The hypothesis that the chemistry of the volatiles implies a specialized plant-pollinator co-evolution was confirmed by a significant regression (p < 0.05), which showed an inverse relationship between chemical diversity (H’) and pollinator dominance (D) indexes. The chemical specificity indicates the specificity of pollinators and vice versa.