Parallel and nonparallel ecological, morphological and genetic divergence in lake-stream stickleback from a single catchment

Parallel phenotypic evolution in similar environments has been well studied in evolutionary biology; however, comparatively little is known about the influence of determinism and historical contingency on the nature, extent and generality of this divergence. Taking advantage of a novel system containing multiple lake-stream stickleback populations, we examined the extent of ecological, morphological and genetic divergence between three-spined stickleback present in parapatric environments. Consistent with other lake-stream studies, we found a shift towards a deeper body and shorter gill rakers in stream fish. Morphological shifts were concurrent with changes in diet, indicated by both stable isotope and stomach contents analysis. Performing a multivariate test for shared and unique components of evolutionary response to the distance gradient from the lake, we found a strong signature of parallel adaptation. Nonparallel divergence was also present, attributable mainly to differences between river locations. We additionally found evidence of genetic substructuring across five lake-stream transitions, indicating that some level of reproductive isolation occurs between populations in these habitats. Strong correlations between pairwise measures of morphological, ecological and genetic distance between lake and stream populations supports the hypothesis that divergent natural selection between habitats drives adaptive divergence and reproductive isolation. Lake-stream stickleback divergence in Lough Neagh provides evidence for the deterministic role of selection and supports the hypothesis that parallel selection in similar environments may initiate parallel speciation.

Freshwater pearl mussels show plasticity of responses to different predation risks but also show consistent individual differences in responsiveness

Animals often show behavioural plasticity with respect to predation risk but also show behavioural syndromes in terms of consistency of responses to different stimuli. We examine these features in the freshwater pearl mussel. These bivalves often aggregate presumably to reduce predation risk to each individual. Predation risk, however, will be higher in the presence of predator cues. Here we use dimming light, vibration and touch as novel stimuli to examine the trade-off between motivation to feed and motivation to avoid predation. We present two experiments that each use three sequential novel stimuli to cause the mussels to close their valves and hence cease feeding. We find that mussels within a group showed shorter closure times than solitary mussels, consistent with decreased vulnerability to predation in group-living individuals. Mussels exposed to the odour of a predatory crayfish showed longer closures than control mussels, highlighting the predator assessment abilities of this species. However, individuals showed significant consistency in their closure responses across the trial series, in line with behavioural syndrome theory. Our results show that bivalves trade-off feeding and predator avoidance according to predation risk but the degree to which this is achieved is constrained by behavioural consistency. © 2011 Elsevier B.V.

Morphological cladistic analysis as a model for character evaluation in primitive living chitons (Polyplacophora, Lepidopleurina)

Chitons are often referred to as "living fossils" in part because they are proposed as one of the earliest-diverging groups of living molluscs, but also because the gross morphology of the polyplacophoran shell has been conserved for hundreds of millions of years. As such, the analysis of evolution and radiation within polyplacophorans is of considerable interest not only for resolving the shape of pan-molluscan phylogeny but also as model organisms for the study of character evolution. This study presents a new, rigorous cladistic analysis of the morphological characters used in taxonomic descriptions for chitons in the living suborder Lepidopleurina Thiele, 1910 (the earliest-derived living group of chitons). Shell-based characters alone entirely fail to recover any recognized subdivisions within the group, which may raise serious questions about the application of fossil data (from isolated shell valves). New analysis including characters from girdle armature and gill arrangements recovers some genera within the group but also points to the lack of monophyly within the main genus Leptochiton Gray, 1847. Additional characters from molecular data and soft anatomy, used in combination, are clearly needed to resolve questions of chiton relationships. However, the data sets currently available already provide interesting insights into the analytical power of traditional morphology as well as some knowledge about the early evolution and radiation of this group.

Genetic and morphological characterization of Cladobotryum species causing cobweb disease of mushrooms

Cladobotryum dendroides (= Dactylium dendroides) has hitherto been regarded as the major causal agent of cobweb disease of the cultivated mushroom, Agaricus bisporus. Nucleotide sequence data for the internal transcribed spacer (ITS) regions of four Cladobotryum/Hypomyces species reported to be associated with cobweb disease, however, indicate that the most common pathogen is now C. mycophilum. This cobweb pathogen varies somewhat in conidial septation from published descriptions of C. mycophilum and lacks the distinctive colony odor. ITS sequencing revealed minor nucleotide variation which split isolates of the pathogen into three subgroups, two comprising isolates that were sensitive to methylbenzimidazole carbamate (MBC) fungicides and one comprising MBC-resistant isolates. The MBC-resistant isolates, which were only obtained from Ireland and Great Britain, clustered together strongly in randomly amplified polymorphic DNA (RAPD) PCR analysis, suggesting that they may be clonal. The MBC-sensitive isolates were more diverse. A RAPD fragment of 800 to 900 bp, containing a microsatellite and found in the MBC-resistant isolates, also indicated their clonal nature; the microsatellites of these isolates contained the same number of GA repeats. Smaller, polymorphic microsatellites, similarly comprising GA repeats, in the MBC-sensitive isolates in general correlated with their geographic origin.

Molecular Phylogenies Support Homoplasy of Multiple Morphological Characters Used in the Taxonomy of Heteroscleromorpha (Porifera: Demospongiae)

Sponge classification has long been based mainly on morphocladistic analyses but is now being greatly challenged by more than 12 years of accumulated analyses of molecular data analyses. The current study used phylogenetic hypotheses based on sequence data from 18S rRNA, 28S rRNA, and the CO1 barcoding fragment, combined with morphology to justify the resurrection of the order Axinellida Lévi, 1953. Axinellida occupies a key position in different morphologically derived topologies. The abandonment of Axinellida and the establishment of Halichondrida Vosmaer, 1887 sensu lato to contain Halichondriidae Gray, 1867, Axinellidae Carter, 1875, Bubaridae Topsent, 1894, Heteroxyidae Dendy, 1905, and a new family Dictyonellidae van Soest et al., 1990 was based on the conclusion that an axially condensed skeleton evolved independently in separate lineages in preference to the less parsimonious assumption that asters (star-shaped spicules), acanthostyles (club-shaped spicules with spines), and sigmata (C-shaped spicules) each evolved more than once. Our new molecular trees are congruent and contrast with the earlier, morphologically based, trees. The results show that axially condensed skeletons, asters, acanthostyles, and sigmata are all homoplasious characters. The unrecognized homoplasious nature of these characters explains much of the incongruence between molecular-based and morphology-based phylogenies. We use the molecular trees presented here as a basis for re-interpreting the morphological characters within Heteroscleromorpha. The implications for the classification of Heteroscleromorpha are discussed and a new order Biemnida ord. nov. is erected.

On Irish stickleback:Morphological diversification in a secondary contact zone

Question: How parallel is adaptive evolution when it occurs from different genetic backgrounds? Background: Divergent evolutionary lineages of several post-glacial fish species including the threespine stickleback are found together in Ireland. Goals: To investigate the morphological diversity of stickleback populations in Ireland and assess whether morphology evolved in parallel between evolutionary lineages. Methods: We sampled stickleback from lake, river, and coastal habitats across Ireland. Microsatellite and mitochondrial DNA data revealed evolutionary history. Geometric morphometrics and linear trait measurements characterized morphology. We used a multivariate approach to quantify parallel and non-parallel divergence within and between lineages. Results: Repeated evolution of similar morphologies in similar habitats occurred across Ireland, concordant with patterns observed elsewhere in the stickleback distribution. A strong pattern of habitat-specific morphology existed even among divergent lineages. Furthermore, a strong signal of shared morphological divergence occurred along a marine-freshwater axis. Evidently, deterministic natural selection played a more important role in driving freshwater adaptation than independent evolutionary history. © 2013 Mark Ravinet.

Morphological consequences of lateral outfracture of the inferior turbinate

Objective: We report three cases of lateral outfracture of the inferior turbinate, which demonstrate a range of changes in the size, position and shape of the inferior turbinate.

Method: During a study of the validity of computer modelling of nasal airflow, computed tomography scans of the noses of patients who had undergone lateral outfracture of the inferior turbinate were collected. The pre-operative scan was compared with the post-operative scan six weeks later.

Results: In one patient, there was only a small lateral displacement of the inferior turbinate. In the other two cases, appreciable reduction in the volume of one inferior turbinate was noted, in addition to minor changes in the shape.

Conclusion: Lateral outfracture of the inferior turbinate produces varied and inconsistent changes in morphology which may affect the shape, size and position of the turbinate.

Incipient plasticity in 4H-SiC during quasistatic nanoindentation

Silicon carbide (SiC) is an important orthopaedic material due to its inert nature and superior mechanical and tribological properties. Some of the potential applications of silicon carbide include coating for stents to enhance hemocompatibility, coating for prosthetic-bearing surfaces and uncemented joint prosthetics. This study is the first to explore nanomechanical response of single crystal 4H-SiC through quasistatic nanoindentation. Displacement controlled quasistatic nanoindentation experiments were performed on single crystal 4H-SiC specimen using a blunt Berkovich indenter (300 nm tip radius) at extremely fine indentation depths of 5 nm, 10 nm, 12 nm, 20 nm, 25 nm and 50 nm. Load-displacement curve obtained from the indentation experiments showed yielding or incipient plasticity in 4H-SiC typically at a shear stress of about 21 GPa (~an indentation depth of 33.8 nm) through a pop-in event. An interesting observation was that the residual depth of indent showed three distinct patterns: (i) Positive depth hysteresis above 33 nm, (ii) no depth hysteresis at 12 nm, and (iii) negative depth hysteresis below 12 nm. This contrasting depth hysteresis phenomenon is hypothesized to originate due to the existence of compressive residual stresses (upto 143 MPa) induced in the specimen by the polishing process prior to the nanoindentation

Macrophages Control Vascular Stem/Progenitor Cell Plasticity Through Tumor Necrosis Factor-α-Mediated Nuclear Factor-κB Activation

Objective: Vascular lineage differentiation of stem/progenitor cells can contribute to both tissue repair and exacerbation of vascular diseases such as in vein grafts. The role of macrophages in controlling vascular progenitor differentiation is largely unknown and may play an important role in graft development. This study aims to identify the role of macrophages in vascular stem/progenitor cell differentiation and thereafter elucidate the mechanisms that are involved in the macrophage- mediated process.

Approach and Results: We provide in vitro evidence that macrophages can induce endothelial cell (EC) differentiation of the stem/progenitor cells while simultaneously inhibiting their smooth muscle cell differentiation. Mechanistically, both effects were mediated by macrophage-derived tumor necrosis factor-α (TNF-α) via TNF-α receptor 1 and canonical nuclear factor-κB activation. Although the overexpression of p65 enhanced EC (or attenuated smooth muscle cell) differentiation, p65 or TNF-α receptor 1 knockdown using lentiviral short hairpin RNA inhibited EC (or rescued smooth muscle cell) differentiation in response to TNF-α. Furthermore, TNF-α–mediated EC differentiation was driven by direct binding of nuclear factor-κB (p65) to specific VE-cadherin promoter sequences. Subsequent experiments using an ex vivo decellularized vessel scaffold confirmed an increase in the number of ECs and reduction in smooth muscle cell marker expression in the presence of TNF-α. The lack of TNF-α in a knockout mouse model of vein graft decreased endothelialization and significantly increased thrombosis formation.

Conclusions: Our study highlights the role of macrophages in directing vascular stem/progenitor cell lineage commitment through TNF-α–mediated TNF-α receptor 1 and nuclear factor-κB activation that is likely required for endothelial repair in vascular diseases such as vein graft.

Control of morphological properties of porous biodegradable scaffolds processed by supercritical CO2 foaming

A low cost supercritical CO foaming rig with a novel design has been used to prepare fully interconnected and highly porous biodegradable scaffolds with controllable pore size and structure that can promote cancellous bone regeneration. Porous polymer scaffolds have been produced by plasticising the polymer with high pressure CO and by the formation of a porous structure following the escape of CO from the polymer. Although, control over pore size and structure has been previously reported as difficult with this process, the current study shows that control is possible. The effects of processing parameters such as CO saturation pressure, time and temperature and depressurisation rate on the morphological properties, namely porosity, pore interconnectivity, pore size and wall thickness- of the scaffolds have been investigated. Poly(d,l)lactic acid was used as the biodegradable polymer. The surfaces and internal morphologies of the poly(d,l)lactic acid scaffolds were examined using optical microscope and micro computed tomography. Preosteoblast human bone cells were seeded on the porous scaffolds in vitro to assess cell attachment and viability. The scaffolds showed a good support for cell attachment, and maintained cell viability throughout 7 days in culture. This study demonstrated that the morphology of the porous structure can be controlled by varying the foaming conditions, allowing the porous scaffolds to be used in various tissue engineering applications.

Morphological study of the uncommon rectus sterni muscle in German cadavers

Objective: The present investigation has been designed to study the incidence of the rectus stern muscle in German human cadavers dissected in the Kingdom of Saudi Arabia, trying to find a postulation for the development of such muscle when present. Design: Gross dissection of 130 cadavers, of both sexes, was performed throughout a period of 10 years. Setting: Department of Anatomy College of Medicine, King Faisal University, Dammam, Saudi Arabia. Intervention: Investigation of the origin and insertion of the rectus sterni and measurements of its length and width. Results: Two adult cadavers, one of each sex, had shown well-developed bilateral rectus stern muscles. All muscles identified were parasternal in position, being superficial to the medial portion of the pectoralis major muscle. Minor morphological differences were observed among the four muscle masses concerning their length, breadth, origin and insertion. Conclusion: The current study has determined the incidence of the rectus sterni muscle, in German cadavers to be 1.54% per bodies examined compared to 4% in cadavers from Saudis. Such a frequency is compared to that reported in different geographic populations. The rectus sterni muscle is innervated by the anterior cutaneous branches of the intercostal nerves. The description of the rectus sterni muscle and its incidence determined in the present study, might be of a great help for clinicians radiographing or tackling the pectoral region.