Jane Lewis

We report the zygotic encystment of geographically dispersed isolates in the dinoflagellate species complex Alexandrium tamarense, in particular, successful mating of toxic Group I and nontoxic Group III isolates. However, hypnozygotes produced in Group I/III co-cultures complete no more than three divisions after germinating. Previous reports have suggested a mate recognition mechanism whereby hypnozygotes produced in co-cultures could arise from either homotypic (inbred) or heterotypic (outbred) gamete pairs. To determine the extent to which each occurs, a nested PCR assay was developed to determine parentage of individual hypnozygotes. The vast majority of hypnozygotes from pairwise Group I/III co-cultures were outbred, so that inviability was a result of hybridization, not inbreeding. These findings support the assertion that complete speciation underlies the phylogenetic structure of the Alexandrium tamarense species complex. Additionally, the ribosomal DNA (rDNA) copy numbers of both hybrid and single ribotype hypnozygotes were reduced substantially from those of haploid motile cells. The destruction of rDNA loci may be crucial for the successful mating of genetically distant conjugants and appears integral to the process of encystment. The inviability of Group I/III hybrids is important for public health because the presence of hybrid cysts may indicate ongoing displacement of a nontoxic population by a toxic one (or vice versa). Hybrid inviability also suggests a bloom control strategy whereby persistent, toxic Group I blooms could be mitigated by introduction of nontoxic Group III cells. The potential for hybridization in nature was investigated by applying the nested PCR assay to hypnozygotes from Belfast Lough, Northern Ireland, a region where Group I and III populations co-occur. Two hybrid cysts were identified in 14 successful assays, demonstrating that Group I and III populations do interbreed in that region. However, an analysis of mating data collected over an 18-year period indicated a leaky pre-mating barrier between ribosomal species (including Groups I and III). Whether the observed selectivity inhibits hybridization in nature is dependent on its mechanism. If the point of selectivity is the induction of gametogenesis, dissimilar ribotypes could interbreed freely, promoting displacement in cases where hybridization is lethal. If instead, selectivity occurs during the adhesion of gamete pairs, it could enable stable coexistence of A. tamarense species. In either case, hybrid inviability may impose a significant obstacle to range expansion. The nested PCR assay developed here is a valuable tool for investigation of interspecies hybridization and its consequences for the global biogeography of these important organisms.

Page 1. 1289 Elbrächter & al. • Agenda for Calcareous Dinoflagellate Research TAXON 57 (4) • November 2008: 1289–1303 INTRODUCTION The distinct character unifying calcareous dinoflagel-lates is the production of calcified ...

Microalgae in marine and brackish waters of Europe regularly cause harmful effects, considered from the human perspective, in that they cause economic damage to fisheries and tourism. Cyanobacteria cause similar problems in freshwaters. These episodes encompass a broad range of phenomena collectively referred to as harmful algal blooms (HABs). For adequate management of these phenomena, monitoring of microalgae is required. However, present day monitoring is time consuming and based on morphology as determined by light microscopy, which may be insufficient to give definitive species and toxin attribution. In the European Union (EU) FP7 project MIDTAL (microarrays for the detection of toxic algae), we will first target rapid species identification using rRNA genes. The variable regions of the rRNA genes can be used for probe design to recognize species or even strains. Second, a toxin based microarray will be developed that includes antibody reactions to specific toxins produced by t...

Alexandrium minutum is a globally distributed harmful algal bloom species with many strains that are known to produce paralytic shellfish toxins (PSTs) and consequently represent a concern to human and ecosystem health. This review highlights that A. minutum typically occurs in sheltered locations, with cell growth occurring during periods of stable water conditions. Sediment characteristics are important in the persistence of this species within a location, with fine sediments providing cyst deposits for ongoing inoculation to the water column. Toxic strains of A. minutum do not produce a consistent toxin profile, different populations produce a range of PSTs in differing quantities. Novel cluster analysis of published A. minutum toxin profiles indicates five PST profile clusters globally. Some clusters are grouped geographically (Northern Europe) while others are widely spread. Isolates from Taiwan have a range of toxin profile clusters and this area appears to have the most diver...

... 0.05) level. There was a significant effect of temperature and salinity on central body length (Fig. 7, A–C) and width (Fig. 7 ... be found. There was a significant effect of salinity on process length (Fig. 9) but no temperature effect. The ...

... of Gonyauiax spingifera (as Peridinittm spinrferttm) by Claparéde and Lachrnann (I85?) This species, of small © 1999 Taylor & Francis. ... from other areas and have been related to variations in environmental variables, particularly salinity (Dale 1996, Ellegaard 1996, Nehring ...

ABSTRACT Surface sculpture of spores, pollen and other walled microscopic organisms commonly resembles patterns seen elsewhere in nature. These patterns are often species specific and of significant use in taxonomic study, particularly so in the fossil record where other data may be minimal. It can be argued that patterning, which must be governed to some extent by genotype, could simply reflect other natural patterns as a result of physical and chemical interaction during development. But does this diminish the view that patterning can often perform important biological functions? With examples drawn from fossil and living walled structures, we analyse the complex relationship between genetic constraints, construction mechanism and biological function, and we conclude that similar function may often result in similar pattern, perhaps further enhanced by similar aspects of development. The genetic complement, by way of selection, ‘learns’ to repeat the pattern, but each pattern creation mechanism retains a ‘personal signature’ reflecting its evolutionary history. With this new perspective in mind, we assess the potential implications in the study of Palaeozoic microfossils when many different groups are first developing surface patterning.

The fine structure of the planozygotes and encystment of Scrippsiella sp. have been studied by scanning and transmission electron microscopy. The planozygote is armoured and has two longitudinal flagella and one transverse flagellum. Unlike the vegetative cell, the planozygote has two pairs of basal bodies, large numbers of starch granules and many vesicles containing electron-dense particles. The build-up of storage

ABSTRACT Structural development of newly excysted cells of Gonyaulax polyedra was investigated by scanning and transmission electron microscopy for the first time. Cells of known age were processed for TEM using a thin-film encapsulation technique. 0–1 hour post-excystment cells were of striking ultrastructural maturity. Unusual features included large quantities of “guanine” crystals and lipids: chloroplasts with atypical arrangement of lamellae and nuclear “blebs”. The fine structure of 8–9 h post-excystment cells closely resembled that previously described for cultured cells of this species. Thecal development, as shown by SEM, was extremely rapid; 1–2 h post-excystment cells had a complete plate tabulation and the beginnings of thecal sculpturing. Thereafter thecal architecture was consolidated and 12–13 h post-excystment cells had developed the typical heavy sculpturing characteristic of this species.

ABSTRACT Alexandrium tamarense is a cyst-forming dinoflagellate that can cause toxicity in shellfish. Belfast Lough, in northeast Ireland, has experienced toxicity events due to the presence of A. tamarense, which are monitored because of shellfish farms in the Lough. Since 1992 anthropogenic influences on the Lough have changed with the introduction of a ‘fast cat’ ferry service and an increase in mussel farming. In 2002 Belfast Lough was surveyed for A. tamarense cyst distribution in the sediments and the results are compared to a previous cyst survey carried out in the Lough in 1992. Cyst numbers were generally lower in 2002 than in 1992 (t-test, P −1 dry sediment compared with 3330 in 1992. Although sediment disturbance increased in the period between the surveys and plays a role in cyst distribution, A. tamarense cysts are still present in the seabed of the Lough. These cysts remain an important repository of inoculating cells for A. tamarense blooms that have not been removed by the recent anthropogenic activity in the Lough and therefore the requirement for monitoring remains. Comparisons between cyst counts per volume of wet sediment and per weight of dry sediment were carried out, and although the first is needed for ecological studies allowing a deeper analysis, it is also recommended that cyst counts per dry weight of sediment are always reported for wider comparative purposes.

... thorianum (Paulsen) Balech 50 60 Brigantedinium majusculum Reid 50-92 Gotius abei Matsuoka 54 Protoperidinium denticulatum (Gran & Braarud) Balech 56-76 Data taken from Wall & Dale (1968); Matsuoka (1976); Reid (1977); Harland (1982); Lewis, Dodge & Tett (1984 ...

... Chatton & Biecheler; 7-( Seligo) Chatton; S-Lebour; 9-Schiller; 10-Hulburt; ll-Lamarck; 12-Lindemann; 13-Nygaard; 14-Lemmermann; 15-von Stosch; 16-KJebs; 17-Howell; IS Anissimowa; 19-( Levander) Lemmermann; 20-Stein; 21-Lemmermann; 22-Huitfeld-Kass; 23-( ...

... JANE LEWlS1*, GAY KENNAWAyl, SUSANA FRANCA2 AND ELSA ALVERCA2 'Applied Ecology Research Group, School of Biosciences, University of Westminster ... There have been a few stud ies describing the ultrastructure of this transformation (Alex andrium Halim: Fritz et at ...

The germination characteristics of Alexandrium minutum cysts from the Fal estuary were studied at different conditions of temperature (4–24 °C) and salinity (15–35‰) and in the dark and low light intensity (2 μmol −2 s −1 ). Sediment sub-samples were directly cultured and ...

I can well remember my delight and bewilderment some thirty years ago when I first looked at interstitial water from a sandy shore. A fascinating world of (to my eyes) bizarrely shaped and highly active organisms was revealed, none of which I was familiar with, despite having studied planktonic dinoflagellates for some time. A painful assembly of literature from diverse and obscure journals followed in order to approach some understanding of this fascinating community. So this book is an extremely welcome first guide to the marine benthic dinoflagellates, bringing together the expertise of four authors from around the world who have worked extensively on this group of diverse and special organisms.This article is protected by copyright. All rights reserved.