Development and application of an immunoassay diagnostic technique for studying Hematodinium infections in Nephrops norvegicus populations. (49/633)

Patent Hematodinium infections of the Norway lobster Nephrops norvegicus can be detected with a morphological method (pleopod diagnosis), but this fails to identify low-level haemolymph (sub-patent) and any tissue-based (latent) infections. The current study describes the development and application of an immunoassay for the detection of antigens of the parasite Hematodinium in the Norway lobster N. norvegicus. Infected tissue and haemolymph samples were detected as multiple-band reactions to a polyclonal antibody (anti-Hematodinium). The sensitivity limit of the method was 204 parasites mm(-3), approximately 10 times more sensitive than the pleopod diagnosis method. Use of the immunoassay on tissue samples taken from catches in the Clyde Sea area, Scotland, UK, showed that the pleopod method considerably under-diagnosed infection prevalence in the early part of the season, though this under-diagnosis decreased as infected lobsters in the field progressed from latent and sub-patent to patent infections. However, the immunoassay failed to detect any infected lobsters during the summer months, suggesting that infection may not be carried over from one season to the next. The data presented suggest that this immunoassay allows for the accurate estimation of Hematodinium infection prevalence in the field and should be employed, where possible, for the routine monitoring of infection prevalence in N. norvegicus.  (+info)

Total synthesis of ciguatoxin CTX3C. (50/633)

More than 20,000 people suffer annually from ciguatera seafood poisoning in subtropical and tropical regions. The extremely low content of the causative neurotoxins, designated as ciguatoxins, in fish has hampered the isolation, detailed biological studies, and preparation of anti-ciguatoxin antibodies for detecting these toxins. The large (3 nanometers long) and complicated molecular structure of ciguatoxins has impeded chemists from completing their total synthesis. Our highly convergent strategic approach featuring the chemoselective ring-closing metathesis reaction as a key tactic has enabled the total synthesis of ciguatoxin CTX3C, which will provide a practical supply for further studies.  (+info)

Zooxanthellae of the Montastraea annularis species complex: patterns of distribution of four taxa of Symbiodinium on different reefs and across depths. (51/633)

Corals of the Montastraea annularis complex host several different dinoflagellates in the genus Symbiodinium. Here we address two questions arising from our previous studies of these associations on an offshore reef. First, do the same taxa and patterns of association (Symbiodinium A and B found in higher irradiance habitats than Symbiodinium C) occur on an inshore reef? Second, does M. franksi at the limits of its depth range host only Symbiodinium C, as it does at intermediate depths? In both surveys, a new Symbiodinium taxon and different patterns of distribution (assayed by analyses of small ribosomal subunit RNA genes [srDNA]) were observed. Inshore, a taxon we name Symbiodinium E predominated in higher irradiance habitats in M. franksi and its two sibling species; the only other zooxanthella observed was Symbiodinium C. Offshore, M. franksi mainly hosted Symbiodinium C, but hosted Symbiodinium A, B, C, and E in shallow water and Symbiodinium E and C in very deep water. Symbiodinium E may be stress-tolerant. Observed srDNA heterogeneity within samples of Symbiodinium B, C, and E is interpreted as variation across copies within this multigene family. Experimental bleaching of Symbiodinium C supported this interpretation. Thus sequences from natural samples should be interpreted cautiously.  (+info)

Repopulation of Zooxanthellae in the Caribbean corals Montastraea annularis and M. faveolata following experimental and disease-associated bleaching. (52/633)

Caribbean corals of the Montastraea annularis species complex associate with four taxa of symbiotic dinoflagellates (zooxanthellae; genus Symbiodinium) in ecologically predictable patterns. To investigate the resilience of these host-zooxanthella associations, we conducted field experiments in which we experimentally reduced the numbers of zooxanthellae (by transplanting to shallow water or by shading) and then allowed treated corals to recover. When depletion was not extreme, recovering corals generally contained the same types of zooxanthellae as they did prior to treatment. After severe depletion, however, recovering corals were always repopulated by zooxanthellae atypical for their habitat (and in some cases atypical for the coral species). These unusual zooxanthellar associations were often (but not always) established in experimentally bleached tissues even when adjacent tissues were untreated. Atypical zooxanthellae were also observed in bleached tissues of unmanipulated Montastraea with yellow-blotch disease. In colonies where unusual associations were established, the original taxa of zooxanthellae were not detected even 9 months after the end of treatment. These observations suggest that zooxanthellae in Montastraea range from fugitive opportunists and stress-tolerant generalists (Symbiodinium A and E) to narrowly adapted specialists (Symbiodinium B and C), and may undergo succession.  (+info)

Structure elucidation of ostreocin D, a palytoxin analog isolated from the dinoflagellate Ostreopsis siamensis. (53/633)

The structure of ostreocin D, a palytoxin analog isolated from the marine dinoflagellate Ostreopsis siamensis, was found to be 42-hydroxy-3,26-didemethyl-19,44-dideoxypalytoxin by detailed 2D NMR analyses of intact ostreocin D and its ozonolysis products. Partial stereochemical assignments were done. This result indicates that the dinoflagellate O. siamensis is one of the biogenetic origins of palytoxin.  (+info)

Discovery of the toxic dinoflagellate Pfiesteria in northern European waters. (54/633)

Several dinoflagellate strains of the genus Pfiesteria were isolated by culturing techniques from sediment samples taken in the Oslofjord region of Norway. Pfiesteria piscicida, well known as a fish killer from the Atlantic coast of America, was identified by genetic methods and light microscopy. The related species Pfiesteria shumwayae was attracted from the sediment by the presence of fish, and has proved toxic. This present survey demonstrates the wide distribution of these potentially harmful species, but so far they have not been connected with fish kills in Europe.  (+info)

Specificity of a model cnidarian-dinoflagellate symbiosis. (55/633)

To understand the flexibility of symbiotic associations in coral reefs, we investigated the specificity of the Aiptasia (cf. insignis)-Symbiodinium association in the laboratory by rendering the anemones aposymbiotic and inoculating them with different isolates of SYMBIODINIUM: Infective algal symbionts were monitored over 3 months by re-isolation and identification using denaturing-gradient gel electrophoresis and sequence comparison of their amplified 18S rRNA hypervariable V1 + V2 gene region. Despite similarity in their external morphology, the algal isolates differed in their infectivity towards the host. Within days of single-isolate inoculation, aposymbiotic anemones formed associations with fresh or cultured isolates (clade B) from the anemones Aiptasia sp. or A. tagetes, respectively. They associated to a limited extent with cultured isolates (clade A) from the tridacnids Tridacna crocea or Hippopus hippopus, and not at all with a cultured isolate (clade C) from the stony coral Montipora verrucosa, nor with a free-living isolate (clade A) from subtidal sands. Aposymbiotic anemones inoculated with a mixture of all isolates had only the anemone taxon as their detectable symbionts. Re-inoculation of induced symbioses with a mixture of all isolates and incubation with wild anemones showed that the initial induced symbioses with the anemone taxon were stable. Anemones originally infected with tridacnid isolates either additionally acquired the anemone taxon or had the former outgrown by the latter. These results demonstrate the presence of a host-symbiont recognition mechanism, and possibly competition among potential algal symbionts in the Aiptasia-Symbiodinium association. Here we present a method that may be useful in monitoring the algal population dynamics in symbiotic corals in the field, along with an efficient method of rendering Aiptasia aposymbiotic for further laboratory investigation of Aiptasia-Symbiodinium symbioses.  (+info)

Evolution of dinoflagellate unigenic minicircles and the partially concerted divergence of their putative replicon origins. (56/633)

Dinoflagellate chloroplast genes are unique in that each gene is on a separate minicircular chromosome. To understand the origin and evolution of this exceptional genomic organization we completely sequenced chloroplast psbA and 23S rRNA gene minicircles from four dinoflagellates: three closely related Heterocapsa species (H. pygmaea, H. rotundata, and H. niei) and the very distantly related Amphidinium carterae. We also completely sequenced a Protoceratium reticulatum minicircle with a 23S rRNA gene of novel structure. Comparison of these minicircles with those previously sequenced from H. triquetra and A. operculatum shows that in addition to the single gene all have noncoding regions of approximately a kilobase, which are likely to include a replication origin, promoter, and perhaps segregation sequences. The noncoding regions always have a high potential for folding into hairpins and loops. In all six dinoflagellate strains for which multiple minicircles are fully sequenced, parts of the noncoding regions, designated cores, are almost identical between the psbA and 23S rRNA minicircles, but the remainder is very different. There are two, three, or four cores per circle, sometimes highly related in sequence, but no sequence identity is detectable between cores of different species, even within one genus. This contrast between very high core conservation within a species, but none among species, indicates that cores are diverging relatively rapidly in a concerted manner. This is the first well-established case of concerted evolution of noncoding regions on numerous separate chromosomes. It differs from concerted evolution among tandemly repeated spacers between rRNA genes, and that of inverted repeats in plant chloroplast genomes, in involving only the noncoding DNA cores. We present two models for the origin of chloroplast gene minicircles in dinoflagellates from a typical ancestral multigenic chloroplast genome. Both involve substantial genomic reduction and gene transfer to the nucleus. One assumes differential gene deletion within a multicopy population of the resulting oligogenic circles. The other postulates active transposition of putative replicon origins and formation of minicircles by homologous recombination between them.  (+info)