Life cycle evolution:was the eumetazoan ancestor a holoplanktonic, planktotrophic gastraea?

BACKGROUND: Two theories for the origin of animal life cycles with planktotrophic larvae are now discussed seriously: The terminal addition theory proposes a holopelagic, planktotrophic gastraea as the ancestor of the eumetazoans with addition of benthic adult stages and retention of the planktotrophic stages as larvae, i.e. the ancestral life cycles were indirect. The intercalation theory now proposes a benthic, deposit-feeding gastraea as the bilaterian ancestor with a direct development, and with planktotrophic larvae evolving independently in numerous lineages through specializations of juveniles. RESULTS: Information from the fossil record, from mapping of developmental types onto known phylogenies, from occurrence of apical organs, and from genetics gives no direct information about the ancestral eumetazoan life cycle; however, there are plenty of examples of evolution from an indirect development to direct development, and no unequivocal example of evolution in the opposite direction. Analyses of scenarios for the two types of evolution are highly informative. The evolution of the indirect spiralian life cycle with a trochophora larva from a planktotrophic gastraea is explained by the trochophora theory as a continuous series of ancestors, where each evolutionary step had an adaptational advantage. The loss of ciliated larvae in the ecdysozoans is associated with the loss of outer ciliated epithelia. A scenario for the intercalation theory shows the origin of the planktotrophic larvae of the spiralians through a series of specializations of the general ciliation of the juvenile. The early steps associated with the enhancement of swimming seem probable, but the following steps which should lead to the complicated downstream-collecting ciliary system are without any advantage, or even seem disadvantageous, until the whole structure is functional. None of the theories account for the origin of the ancestral deuterostome (ambulacrarian) life cycle. CONCLUSIONS: All the available information is strongly in favor of multiple evolution of non-planktotrophic development, and only the terminal addition theory is in accordance with the Darwinian theory by explaining the evolution through continuous series of adaptational changes. This implies that the ancestor of the eumetazoans was a holopelagic, planktotrophic gastraea, and that the adult stages of cnidarians (sessile) and bilaterians (creeping) were later additions to the life cycle. It further implies that the various larval types are of considerable phylogenetic value

Biomimetic membranes as a technology platform: Challenges and opportunities

Biomimetic membranes are attracting increased attention due to the huge potential of using biological functional components and processes as an inspirational basis for technology development. Indeed, this has led to several new membrane designs and applications. However, there are still a number of issues which need attention. Here, I will discuss three examples of biomimetic membrane developments within the areas of water treatment, energy conversion, and biomedicine with a focus on challenges and applicability. While the water treatment area has witnessed some progress in developing biomimetic membranes of which some are now commercially available, other areas are still far from being translated into technology. For energy conversion, there has been much focus on using bacteriorhodopsin proteins, but energy densities have so far not reached sufficient levels to be competitive with state-of-the-art photovoltaic cells. For biomedical (e.g., drug delivery) applications the research focus has been on the mechanism of action, and much less on the delivery ‘per se’. Thus, in order for these areas to move forward, we need to address some hard questions: is bacteriorhodopsin really the optimal light harvester to be used in energy conversion? And how do we ensure that biomedical nano-carriers covered with biomimetic membrane material ever reach their target cells/tissue in sufficient quantities? In addition to these area-specific questions the general issue of production cost and scalability must also be treated in order to ensure efficient translation of biomimetic membrane concepts into reality

Going home again? Fan nostalgia in anticipation of World of Warcraft Classic

Since its release in 2004, World of Warcraft (WoW) has regularly changed the game and the play experience in significant ways. Recently, Blizzard, the developer of WoW, announced the upcoming game WoW Classic: “an authentic, Blizzard-quality classic experience”. Drawing on interviews with adult WoW fans and gamers, the article examines the game as an ‘affective space’ (Hills, 2002) of fandom that cannot be separated from the fan narratives and experiences it mediates. A key component in this affective space is the notion of fan nostalgia. The nostalgic relationship between a fan and a favourite text is often imbued with an imagined history, conjoining aff ect and meaning, belief and knowledge, and making nostalgia “both a way of knowing worlds – and a discourse of knowledge” (Radstone, 2010, p. 188). The article traces diff erent and often contradictory modes of fan nostalgia connected to WoW, such as tactile feelings of technostalgia (Bolin, 2015), deeply personal and anchoring types of nostalgia in the form of totemic objects (Proctor, 2017), manifested through fan practices of collecting digital items and souvenirs (Geraghty, 2014), and interwoven with desirable and appropriate self-identity and self-narrative (Williams, 2014). In reading these modes of nostalgia, the article argues that they ultimately function as a sort of ‘homecoming’, as the gamers’ many different experiences of the game and media texts surrounding the game all come together as complex attempts of memory work, creating the possibility of establishing a home within their fandom

Fans feeling a disturbance in the Force. Star Wars and the power of paratexts

Ever since Disney acquired Lucasfilm in 2012, the Star Wars franchise has been widely praised for its updated take on and inclusion of diversity (extending in particular to women), having moved away from its image as purely a boys’ club to include everyone. While this may seem true at first glance if we regard the blockbuster films of the Star Wars franchise, such a sentiment proves to be more problematic when we consider the merchandise accompanying the films. This article starts by reading the gender diversity of the Star Wars franchise as “plastic representation” (Warner 2017), branching out to include Star Wars merchandise as paratexts (Genette 1997, Gray 2010, Scott, 2017). Reading Star Wars toys, action figures and play sets as culturally significant objects and markers of fan identity (Geraghtly 2014), I argue that these paratexts serve to bolster gendered franchising and to work as “fanagagement” (Hills 2010) to promote certain types of fan engagement in Star Wars, while at the same time policing others

Modelling Dynamic Topologies via Extensions of VDM-RT

Only a few formal methods include descriptions of the network topology that the modelled system is deployed onto. In VDM Real-Time (VDM-RT) this has been enabled for distributed systems that have a static structure. However, when modelling dynamic systems this fixed topology becomes an issue. Systems with highly distributed and alternating relationships cannot be expressed correctly in a static model. This document describes how VDM-RT can be extended with new language constructs to enable the description of dynamic reconfiguration of the network topology during the runtime execution of a model. The extension is developed on the basis of a case study involving a dynamic system that has a constant changing system topology. With a basis in the case study a model is developed that uses the static version of VDM-RT in order to reveal the limitations of the language. The case study is then revisited where the capabilities of the proposed reconfiguration extension are applied to the model, and the value of having the extension is evaluated. We expect that other notations can benefit from the experiences reported here

A novel approach to probe host-pathogen interactions of bovine digital dermatitis, a model of a complex polymicrobial infection

Background: Polymicrobial infections represent a great challenge for the clarification of disease etiology and the development of comprehensive diagnostic or therapeutic tools, particularly for fastidious and difficult-to-cultivate bacteria. Using bovine digital dermatitis (DD) as a disease model, we introduce a novel strategy to study the pathogenesis of complex infections. Results: The strategy combines meta-transcriptomics with high-density peptide-microarray technology to screen for in vivo-expressed microbial genes and the host antibody response at the site of infection. Bacterial expression patterns supported the assumption that treponemes were the major DD pathogens but also indicated the active involvement of other phyla (primarily Bacteroidetes). Bacterial genes involved in chemotaxis, flagellar synthesis and protection against oxidative and acidic stress were among the major factors defining the disease. Conclusions: The extraordinary diversity observed in bacterial expression, antigens and host antibody responses between individual cows pointed toward microbial variability as a hallmark of DD. Persistence of infection and DD reinfection in the same individual is common; thus, high microbial diversity may undermine the host's capacity to mount an efficient immune response and maintain immunological memory towards DD. The common antigenic markers identified here using a high-density peptide microarray address this issue and may be useful for future preventive measures against DD.Fil: Marcatili, Paolo. Technical University of Denmark; DinamarcaFil: Nielsen, Martin W.. Technical University of Denmark; DinamarcaFil: Sicheritz Ponten, Thomas. Technical University of Denmark; DinamarcaFil: Jensen, Tim K.. Technical University of Denmark; DinamarcaFil: Schafer Nielsen, Claus. Schafer-N ApS; DinamarcaFil: Boye, Mette. Hospital of Southern Jutland; DinamarcaFil: Nielsen, Morten. Technical University of Denmark; Dinamarca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas ; ArgentinaFil: Klitgaard, Kirstine. Technical University of Denmark; Dinamarc