Abstract The finding of the enigmatic pathogen Anisolpidium rosenvingei in the filamentous brown macroalga Pylaiella littoralis presented a unique opportunity to histochemically study the distribution of chitin in this little-known pathogen using FUNGALASE™-F, a fluorescein-labelled chitinase. Chitin was found localised to the exit tube of this pathogen, which infects exclusively reproductive cells of its host. The cytological and phylogenetic implications of this finding are discussed. This paper also reports the first record of this pathogen in the United Kingdom, on the west coast of Scotland.

Giant kelp, Macrocystis pyrifera (Linnaeus) C. Agardh, is the subject of intense breeding studies for marine biomass production and conservation of natural resources. In this context, six gametophyte pairs and a sporophyte offspring of Macrocystis from South America were analyzed by flow cytometry. Minimum relative DNA content per cell (1C) was found in five males. Unexpectedly, nuclei of all female gametophytes contained approximately double the DNA content (2C) of males; the male gametophyte from one locality also contained 2C, likely a spontaneous natural diploid variant. The results illustrate a sex‐specific difference in nuclear DNA content among Macrocystis gametophytes, with the chromosomes of the females in a polytenic condition. This correlates with significantly larger cell sizes in female gametophytes compared to males and resource allocation in oogamous reproduction. The results provide key information for the interpretation of DNA measurements in kelp life cycle stages and prompt further research on the regulation of the cell cycle, metabolic activity, sex determination, and sporophyte development.

Scala is a powerful language that supports a variety of features, but it lacks virtual traits. Virtual traits are class-valued object attributes and can be redefined within subtraits. They support higher-order hierarchies and family polymorphism. This work introduces virtual traits into Scala and explains how to encode virtual traits on top of existing Scala features. We have implemented this encoding using Scala annotation macros and have conducted two small case studies.

Reactive programming with first class time-varying values as in Functional Reactive Programming (FRP) is a powerful paradigm for designing and implementing event-based applications. Existing implementations deal with simple values. Time-varying collections can only propagate whether they have changed or not but not what has changed. This is inefficient compared to fine-grained callback driven logic that propagates incremental changes. In this work, we present a framework, Scala.React, with reactive abstractions for event streams, time-varying values as well as an incremental reactive list. Our reactive lists support both first-order reactivity by means of composition similar to functional collections via |map|, |filter|, |fold| and alike, as well as higher-order reactivity with support for time-varying collection elements. The framework automatically propagates incremental changes and guarantees strong data consistency. We show in examples that our system is convenient to use and performs well.

Programming interactive systems by means of the observer pattern is hard and error-prone yet is still the implementation standard in many production environments. We show how to integrate different reactive programming abstractions into a single framework that help migrate from observer-based event handling logic to more declarative implementations. Our central API layer embeds an extensible higher-order data-flow DSL into our host language. This embedding is enabled by a continuation passing style transformation.

In contrast to batch processing systems, interactive systems require substantial programming effort to continuously synchronize with their environment. We quickly review existing programming systems that address this task. We present scala.react, our approach to embedded reactive programming in Scala which combines many advantages of previous systems. We show how our implementation makes use of dynamic dataflow graphs, delimited continuations and implicit parameters in order to achieve desired semantic guarantees and concise syntax.

Programming interactive systems by means of the observer pattern is hard and error-prone yet is still the implementation standard in many production environments. We present an approach to gradually deprecate observers in favor of reactive programming abstractions. Several library layers help programmers to smoothly migrate existing code from callbacks to a more declarative programming model. Our central high-level API layer embeds an extensible higher-order data-flow DSL into our host language. This embedding is enabled by a continuation passing style transformation.

We describe the implementation of first-class polymorphic delimited continuations in the programming language Scala. We use Scala's pluggable typing architecture to implement a simple type and effect system, which discriminates expressions with control effects from those without and accurately tracks answer type modification incurred by control effects. To tackle the problem of implementing first-class continuations under the adverse conditions brought upon by the Java VM, we employ a selective CPS transform, which is driven entirely by effect-annotated types and leaves pure code in direct style. Benchmarks indicate that this high-level approach performs competitively.

Les genes codant pour l'ARN ribosomique 18S de deux agents pathogenes d'algues brunes, Eurychasma dicksonii et Chytridium polysiphoniae, ont ete sequences afin de clarifier leur position phylogenetique. La sequence d'E. dicksonii se situe toujours a la base des Peronosporomycetes (Oomycetes) avec des valeurs de bootstrap elevees. Cependant elle est clairement separee de celles des autres Oomycetes terrestres ou d'eau douce. Le groupe le plus proche est un clade contenant uniquement des sequences environnementales provenant de sediments marins et de plancton oceanique. Les especes du genre Chytridium, groupees avec plusieurs autres genres (entre autres, Obelidium et Phlyctorhiza), forment un clade qui est voisin des organismes rattaches aux genres Monoblepharis, Rhizophydium, Lacustromyces, Nowakowskiella, Neocallimastix et Spizellomyces, a l'interieur des Chytridiomycetes, une des lignees principales des Eumycetes. La sequence de Chytridium polysiphoniae au contraire, forme avec des sequences environnementales aquatiques ou terrestres, un nouveau clade parmi les Chytridiomycetes, indiquant que la position systematique de cette espece devra etre revue. C. polysiphoniae contient de la chitine dans ses parois tandis que E. dicksonii contient de la cellulose, une composition parietale en accord avec leurs positions phylogenetiques respectives. Ces resultats suggerent qu'Eurychasma et Chytridium pourraient devenir des organismes modeles interessants, etant les seuls representants cultivables et morphologiquement connus d'une biodiversite aquatique tres mal connue ; ceci met en evidence la necessite d'inclure des representants marins dans les etudes phylogenetiques des Oomycetes et des Chytridiomycetes.

SUMMARY The process by which Ectocarpus fasciculatus virus type 1 (EfasV-1) infects zoospores of its brown algal host was studied by electron microscopy. Upon virus attachment to the target cell, the integral membrane component of the viral capsid fuses with the host plasma membrane, and the 140-nm viral DNA-protein core enters the cytosol. Within 5 min after infection, particles resembling viral cores appeared in the nucleus. The entry mechanism of EfasV-1 into the host nucleus remains enigmatic.

Journal of PhycologyVolume 36, Issue 4 p. 788-789 New Textbooks in Phycology Ingo Maier, Ingo Maier Fachbereich BiologieUniversität KonstanzKonstanz, GermanySearch for more papers by this author Ingo Maier, Ingo Maier Fachbereich BiologieUniversität KonstanzKonstanz, GermanySearch for more papers by this author First published: 25 December 2001 https://doi.org/10.1046/j.1529-8817.2000.03642.xRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume36, Issue4August 2000Pages 788-789 RelatedInformation

Ein etwa 100mal aktiveres Sexualpheromon als das Cyclohepta‐1,4‐dien 2 (R = C2H5, Ectocarpen) ist dessen Biosynthesevorstufe 1. Dieses thermolabile, cis‐disubstituierte Cyclopropan ist der eigentliche Signalstoff der marinen Braunalge Ectocarpus siliculosus. Die [3,3]‐sigmatrope Umlagerung von 1 in 2 ist mit einer Halbwertszeit von 21 min bei 18°C die schnellste bekannte Reaktion zur spontanen Inaktivierung eines Sexualpheromons. magnified image

SUMMARYThe distribution of binding sites for the lectins WGA, DSA. RCA I, PNA, AAA, MAA. SNA, GNA. and Con A in gametes of both sexes of the brown alga, Ectocarpus siliculosus (Dillw.) Lyngbye, was investigated by fluorescence microscopy. Digoxigenin‐conjugated lectins and an FITC‐anti‐digoxigenin antibody were used as a high sensitivity detection system. Organelles and other distinct cellular domains could be distinguished by their binding specificities. Glycoconjugates associated with one flagellum were found to be associated with the axoneme by lectin binding to isolated flagellar apparatuses. In addition, changes in the distribution of carbohydrate epitopes during the attachment of gametes to the substratum were revealed by differential lectin binding.

We describe the behaviour of Laminaria digitata spermatozoids under pheromonal stimulation using videomicroscopy and high speed cinematography

Laminaria species form extensive beds on marine rocky coasts of mainly northern hemisphere cold-temperate regions. For example, three species are found together at Helgoland (North Sea): L. digitata, L. hyperborea, and L. saccharina, inhabiting the sublitoral region in about 0-4 m below mean low water spring tide. L. hyperborea is restricted to the deeper region of the kelp zone (1-4, max. 8 m below M.L.W.S.T. at Helgoland) [Lüning 1985], In this plant community, the large Laminaria sporophytes are the ecologically dominating organisms.