Behavioral repertoire of high-shore littorinid snails reveals novel adaptations to an extreme environment.

Species that inhabit high-shore environments on rocky shores survive prolonged periods of emersion and thermal stress. Using two Hong Kong high-shore littorinids (Echinolittorina malaccana and E. radiata) as models, we examined their behavioral repertoire to survive these variable and extreme conditions. Environmental temperatures ranged from 4°C in the cool season to 55.5°C in the hot season, with strong seasonal and daily fluctuations. In the hot season, both species allocated >35% of their activity budgets to stress-mitigating thermoregulatory behaviors (e.g. standing, towering) and relatively small proportions to foraging (<20%) and reproduction (<10%). In the assumedly benign cool season, greater proportions (>70%) of activity budgets were allocated to stress mitigation behaviors (crevice occupation, aggregation formation). Both species exhibited multifunctional behaviors that optimized time use during their tidally-constrained activity window in the hot season. Females mated while foraging when awash by the rising tide, and some males crawled on top of females prior to ceasing movement to form 'towers', which have both thermoregulatory benefits and reduce searching time for mates during subsequent activity. The function of such behaviors varies in a state-dependent manner, for example, the function of trail following changes over an activity cycle from mate searching on rising tides, to stress mitigation on falling tides (aiding aggregation formation), and to both functions through tower formation just before movement stops. Many of these behavioral responses are, therefore, multifunctional and can vary according to local conditions, allowing snails in this family to successfully colonize the extreme high-shore environment.

Antimicrobial activity of essential oils against multidrug-resistant clinical isolates of the Burkholderia cepacia complex.

Members of the Burkholderia cepacia complex (Bcc) are an important cause of opportunistic or nosocomial infections that may be hard to treat due to a high incidence of multidrug resistance. We characterised a collection of 51 clinical isolates from this complex, assigning them to 18 sequence types using multi-locus sequence type analysis. Resistance to eight commonly used antibiotics was assessed using by using agar-dilution assays to calculate MICs and widespread and heterogeneous multidrug resistance was confirmed, with eight strains proving resistant to all antibiotics tested. Disc diffusion screening of antimicrobial activity of a range of plant essential oils against these Bcc isolates identified six oils with significant activity (lavender, lemongrass, marjoram, peppermint, tea tree and rosewood) and broth microdilution assays indicated that of these lemongrass and rosewood oils had the highest activity, with MIC50 values of 0.5% and MIC90 values of 1%. Comparison of MIC and MBC values showed that four of these six oils, including lemongrass and rosewood, were bacteriocidal rather than bacteriostatic in their effects. Qualitative analysis of the four bacteriocidal essential oils via GC/MS indicated the presence of 55 different component compounds, mostly monoterpenes. We assessed selected essential oil components as anti-Bcc agents and demonstrated that terpinen-4-ol and geraniol were effective with MICs of 0.125-0.5% (v/v) and 0.125-1% (v/v), respectively. Time-kill studies indicate that these two alcohols are effective against non-growing cells in an efflux-dependent manner. Analysis of bacterial leakage of potassium ions and 260 nm UV-absorbing material on treatment with terpinen-4-ol and geraniol suggested that the observed anti-Bcc activity was a consequence of membrane disruption. This finding was supported by a gas chromatography analysis of bacterial fatty acid methyl esters, which indicated changes in membrane fatty acid composition caused by terpinen-4-ol and geraniol. These essential oils or oil components may ultimately prove useful as therapeutic drugs, for example to treat Bcc infections in CF patients.

Syndesmosis Stabilisation: Screws Versus Flexible Fixation.

Orthopedic surgery is not short of situations where there is controversy regarding optimum management. Treating ankle syndesmosis injuries is an example where practice varies widely and there are many questions that remain unsatisfactorily answered. When addressing the type of syndesmosis stabilization that is required it is essential to ascertain the extent of instability. Only then can a logical approach to restoring the ankle mortise be achieved. Fixation of fibula shaft fractures and posterior malleolus fractures can restore sufficient stability to render syndesmosis stabilization unnecessary. The indications and techniques for stabilizing the distal tibiofibular joint are reviewed with clinical examples.

Gastrocnemius shortening and heel pain.

Pain and reduced function caused by disorders of either the plantar fascia or the Achilles tendon are common. Although heel pain is not a major public health problem it affects millions of people each year. For most patients, time and first-line treatments allow symptoms to resolve. A proportion of patients have resistant symptoms. Managing these recalcitrant cases is a challenge. Gastrocnemius contracture produces increased strain in both the Achilles tendon and the plantar fascia. This biomechanical feature must be properly assessed otherwise treatment is compromised.

Snails and their trails: the multiple functions of trail-following in gastropods.

Snails are highly unusual among multicellular animals in that they move on a layer of costly mucus, leaving behind a trail that can be followed and utilized for various purposes by themselves or by other animals. Here we review more than 40 years of experimental and theoretical research to try to understand the ecological and evolutionary rationales for trail-following in gastropods. Data from over 30 genera are currently available, representing a broad taxonomic range living in both aquatic and terrestrial environments. The emerging picture is that the production of mucus trails, which initially was an adaptation to facilitate locomotion and/or habitat extension, has evolved to facilitate a multitude of additional functions. Trail-following supports homing behaviours, and provides simple mechanisms for self-organisation in groups of snails, promoting aggregation and thus relieving desiccation and predation pressures. In gastropods that copulate, trail-following is an important component in mate-searching, either as an alternative, or in addition to the release of water- or air-borne pheromones. In some species, this includes a capacity of males not only to identify trails of conspecifics but also to discriminate between trails laid by females and males. Notably, trail discrimination seems important as a pre-zygotic barrier to mating in some snail species. As production of a mucus trail is the most costly component of snail locomotion, it is also tempting to speculate that evolution has given rise to various ways to compensate for energy losses. Some snails, for example, increase energy intake by eating particles attached to the mucus of trails that they follow, whereas others save energy through reducing the production of their own mucus by moving over previously laid mucus trails. Trail-following to locate a prey item or a mate is also a way to save energy. While the rationale for trail-following in many cases appears clear, the basic mechanisms of trail discrimination, including the mechanisms by which many snails determine the polarity of the trail, are yet to be experimentally determined. Given the multiple functions of trail-following we propose that future studies should adopt an integrated approach, taking into account the possibility of the simultaneous occurrence of many selectively advantageous roles of trail-following behaviour in gastropods. We also believe that future opportunities to link phenotypic and genotypic traits will make possible a new generation of research projects in which gastropod trail-following, its multitude of functions and evolutionary trade-offs can be further elucidated.

Revision surgery of the lesser toes.

Surgery of the lesser toes is a difficult balancing act, and revision procedures are challenging. It is vastly preferable that the correct procedure be chosen for the correct patient and performed properly from the outset. The flow charts below (Figs. 23­25) are not a rigid protocol, but rather the authors' personal algorithm, based on their own experience, which may help other surgeons facing a stiff, deformed or flail toe to make a reasoned decision.

Robustness of self-organised systems to changes in behaviour: an example from real and simulated self-organised snail aggregations.

Group or population level self-organised systems comprise many individuals displaying group-level emergent properties. Current theory indicates that individual-level behaviours have an effect on the final group-level behaviour; that is, self-organised systems are sensitive to small changes in individual behaviour. Here we examine a self-organised behaviour in relation to environmentally-driven individual-level changes in behaviour, using both natural systems and computer simulations. We demonstrate that aggregations of intertidal snails slightly decrease in size when, owing to hotter and more desiccating conditions, individuals forage for shorter periods--a seemingly non-adaptive behaviour for the snails since aggregation reduces desiccation stress. This decrease, however, only occurs in simple experimental systems (and simulations of these systems). When studied in their natural and more complex environment, and simulations of such an environment, using the same reduced foraging time, no difference in aggregation behaviour was found between hot and cool days. These results give an indication of how robust self-organised systems are to changes in individual-level behaviour. The complexity of the natural environment and the interactions of individuals with this environment, therefore, can result in self-organised systems being more resilient to individual-level changes than previously assumed.

Minimal incision techniques for acute Achilles repair.

This article reviews minimal incision techniques in the treatment of acutely ruptured Achilles tendon and the results that can be anticipated from these methods. However, lack of robust prospective randomized studies on the treatment of Achilles tendon rupture makes it impossible to draw conclusions on optimal treatment strategies. The bulk of the evidence available suggests that surgical repair reduces rerupture rates compared with non-operatively treated tendon ruptures. Surgery does have potential complications, but as outlined in the article, using a mini-open or percutaneous technique of repair might result in highly satisfactory outcomes with acceptably low complication rates.

Parameterization and prediction of community interaction models using stable-state assumptions and computational techniques: an example from the high rocky intertidal.

Many ecological communities exist in a stable state where, if undisturbed, no net change will occur in the populations or in the interactions between the component parts of the system. In this paper we present computational methods (evolutionary algorithms and random searches) to parameterize mathematical models that describe communities in stable states. The initial parameterization of the model requires only "best guess" estimates for parameters and can therefore be used in data-poor situations. The technique locates the stable state that occurs with minimum deviation from these parameters. Alternative stable states in which the community may exist after a disturbance event can also be assessed using this technique, even though the number of alternative states may be large. Using available but incomplete data from an intertidal grazer/biofilm community, we created a prediction of the dynamics of both a pre- and post-disturbance community. Using limited data, we then predicted the most likely post-disturbance community, which proved to be a good match to experimental data, indicating the usefulness of this technique as a predictive tool.

Self-organization of intertidal snails facilitates evolution of aggregation behavior.

Many intertidal snails form aggregations during emersion to minimize desiccation stress. Here we investigate possible mechanisms for the evolution of such behavior. Two behavioral traits (following of mucus trails, and crevice occupation), which both provide selective advantages to individuals that possess the traits over individuals that do not, result in self-organization of aggregations in crevices in the rock surface. We suggest that the existence of self-organizing aggregations provides a mechanism by which aggregation behavior can evolve. The inclusion of an explicitly coded third behavior, aggregation, in a simulated population produces patterns statistically similar to those found on real rocky shores. Allowing these three behaviors to evolve using an evolutionary algorithm, however, results in aggregation behavior being selected against on shores with high crevice density. The inclusion of broadcast spawning dispersal mechanisms in the simulation, however, results in aggregation behavior evolving as predicted on shores with both high crevice density and low crevice density (evolving in crevices first, and then both in crevices and on flat rock), indicating the importance of environmental interactions in understanding evolutionary processes. We propose that self-organization can be an important factor in the evolution of group behaviors.

Energy saving through trail following in a marine snail.

Most snails and slugs locomote over a layer of mucus and although the resultant mucus trail is expensive to produce, we show that this expense can be reduced by trail following. When tracking over fresh conspecific trails, the marine intertidal snail Littorina littorea (L.) produced only approximately 27% of the mucus laid by marker snails. When tracking over weathered trails, snails adjusted their mucus production to recreate a convex trail profile of similar shape and thickness to the trail as originally laid. Maximum energy saving occurs when following recently laid trails which are little weathered. Many and diverse ecological roles for trail following have been proposed. Energy saving is the only role that applies across the Gastropoda and so may help to explain why trail following is such a well-established behaviour.

Characterisation by X-ray microanalysis of metal granules in the mucus trails of Littorina littorea (Gastropoda) along a putative pollution gradient.

Metal-containing granules in the mucus trails of the marine gastropod Littorina littorea from nine sites in north-east England were analysed for elemental composition by X-ray microanalysis and characterised relative to a putative gradient of pollution. Overall granule density varied significantly between sites, means of 6.5-17.0 per field of view (2688 microm2). Most granules found (64%) were poly-metal of a wide variety of compositions, but could be classified as Si+X, Mg+X, S+X, Na+X, P+Ca, P+Al, where X indicates any other combination of elements. Si+Al+X accounted for 61% of the poly-metal granules found and was considered to be contamination from the beach substratum. In single-metal granule form only Ca, Si, Fe, Ti, Al and Na were found. The most common single-metal granule at each site was of Ca, except at two sites, where the most common single-metal granule was of Si. The densities of these granule types varied between sites but differences were found to be significant only in the case of Si granules. Across all sites, single-metal granules of Si (mean = 2.49 microm +/- 1.44 SD, n = 141) and Ca (2.22 microm +/- 1.08 SD, n = 147) were significantly larger than granules of Fe (1.74 microm +/- 0.95 SD, n = 63) and Ti (1.24 microm +/- 0.52 SD, n = 18). The range of sizes was large: Ca (0.5-6 microm), Si (0.5-10 microm), Fe (0.3-4.1 microm), Ti (0.5-2.5 microm). Between the sites there were significant differences in the size of Fe and Si granules but not Ca or Ti granules. Despite these variations in granule type and size, there was no evidence of a relationship with pollution and consequently a detoxifying function of the mucus trail in metal polluted environments is not apparent.

Metal concentrations in the radula of the common limpet, Patella vulgata L., from 10 sites in the UK.

Metal (Al, As, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Pb, Zn) levels in the feeding organ or radula of the common limpet Patella vulgata L. were surveyed in 10 populations over a approximately 150-km stretch of coastline in north-east England. The most northern population was at Beadnell in Northumberland and the most southern was at Port Mulgrave in North Yorkshire; sites included unspoilt bays and areas heavily affected by industrial contamination such as the River Tees estuary. We hypothesized that the radula might be used as an indicator of environmental contamination. There were significant differences between the sites in the ratio of radula length to shell length. Limpets from Whitburn had the smallest radula fraction (mean = 1.665), while those from Port Mulgrave the largest (mean = 1.998). Such variation is common in the literature and we detected no correlate and propose no cause. Iron was clearly the dominant metal in the radulae, with an overall of mean of 1.46% of radular weight, though this is rather low in comparison to values in the literature. Iron is naturally secreted into the developing radula as a putative hardening agent. The next most abundant metals, in descending order, were Na (at approximately 2000-8000 microg g(-1)), K, Mg, Ca (approximately 1000-1500 microg g(-1)), Zn, Cu, Al, Pb (approximately 7-75 microg g(-1)), Mn, As, Cd (approximately 0-1 microg g(-1)). All but Al and Cd showed significant differences between the sites, but not in any consistent or convincing geographic manner. Nevertheless, the variations in metal levels between sites (e.g. Fe > 72%, Cu and Zn > 10-fold) suggest an environmental cause, but we are unable to offer any responsible factor, for example, there appeared little effect of the River Tees estuary. Cadmium is at a relatively low level in the radula in comparison to published data on pedal mucus and the flesh, but Pb is relatively high in pedal mucus and the radula and this might suggest that the radula is a detoxification route for Pb. Although the relationship between radula metal content and environmental metal content is unknown, the radula is constantly replaced and so may yet have the potential to be of use as a bioindicator, integrating metal exposure over much shorter periods than whole body burdens.

Perioperative complications of the Scarf osteotomy.

We reporting the perioperative complications during our early experience using the Scarf osteotomy to correct hallux valgus. A case note review was carried out for the first 100 Scarf osteotomy procedures completed by the senior author. There were six patients (6%) with perioperative complications. Four of these were intraoperative complications including a split first metatarsal in three cases, a shearing of the K-wire in one case and there were two cases of postoperative stress fracture. These complications should be considered by those beginning to master the Scarf osteotomy procedure and by surgeons teaching surgical trainees.