Morphology,phylogeny and toxin profiles of Gymnodinium inusitatum sp. nov., Gymnodinium catenatum and Gymnodinium microreticulatum (Dinophyceae) from the Yellow Sea,China

Four Gymnodinium species have previously been reported to produce microreticulate cysts. Worldwide, Gymnodinium catenatum strains are conservative in terms of larger subunit (LSU) rDNA and internal transcribed spacer region (ITS) sequences, but only limited information on the molecular sequences of other species is available. In the present study, we explored the diversity of Gymnodinium by incubating microreticulate cysts collected from the Yellow Sea off China. A total of 18 strains of Gymnodinium, from three species, were established. Two of these were identified as Gymnodinium catenatum and Gymnodinium microreticulatum, and the third was described as a new species, Gymnodinium inusitatum. Motile cells of G. inusitatum are similar to those of Gymnodinium trapeziforme, but they only share 82.52% similarity in LSU sequences. Cysts of G. inusitatum are polygonal in shape, with its microreticulate wall composed of approximately 14 concave sections. G. microreticulatum strains differ from each other at 69 positions (88.00% similarity) in terms of ITS sequences, whereas all G. catenatum strains share identical ITS sequences and belonged to the global populations. Phylogenetic analyses, based on LSU sequences, revealed that Gymnodinium species that produce microreticulate cysts are monophyletic. Nevertheless, the genus as a whole appears to be polyphyletic. Paralytic shellfish toxins (PSTs) were found in all G. catenatum strains tested (dominated by 11-hydroxysulfate benzoate analogs and N-sulfocarmaboyl analogs) but not in any of the G. microreticulatum and G. inusitatum strains. Our results support the premise that cyst morphology is taxonomically informative and is a potential feature for subdividing the genus Gymnodinium.     

Gymnodinium catenatum Graham (Dinophyceae)in Europe: a growing problem?

The microreticulate resting cyst of the potentially toxic, chain-forming,unarmoured neritic dinoflagellate Gymnodinium catenalum Graham1943. the planktonic stage of which is not known from NorthEuropean waters, is reported for the first time from recentGerman coastal sediments of the North Sea and Baltic Sea. Insandy mud sediments of the German Bight, a maximum of 8 5 livingcysts cm^–3 were found. In Kiel Bight sediments G.catenalumwas found in maximum concentrations of 17.0 living cysts cm^–3.In surface waters of the German Bight resuspended G catenatumcysts were observed at concentrations of up to 3.6 cysts l^–1.Successful germination experiments conducted with natural seawatershow that the occurrence of a vegetative form of G.catenatumin northern Europe is very likely. The present study highlightsthat cyst surveys provide an important tool for the evaluationof areas with potential toxicity problems, as they may indicatethe presence of hitherto overlooked species in the water column.     

Characterization of paralytic shellfish toxins in seawater and sardines (<Emphasis Type="Italic">Sardina pilchardus</Emphasis>) during blooms of <Emphasis Type="Italic">Gymnodinium catenatum</Emphasis>

The re-emergence of Gymnodinum catenatum blooms after a 10 year hiatus of absence initiated the present investigation. This study aims to evaluate the exposure of small pelagic fishes to paralytic shellfish toxins (PST) during blooms of G. catenatum. Sardines (Sardina pilchardus) were selected as a representative fish species. In order to assess toxin availability to fish, both intracellular PSTs (toxin retained within the algal cells) and extracellular PSTs (toxin found in seawater outside algal cells) were quantified, as well as toxin levels within three fish tissue matrices (viscera, muscle and brain). During the study period, the highest cell densities of G. catenatum reached 2.5 × 10⁴ cells l⁻¹ and intracellular PST levels ranged from 3.4 to 398 ng STXeq l⁻¹ as detected via an enzyme linked immunosorbent assay (ELISA). Measurable extracellular PSTs were also detected in seawater (0.2–1.1 μg STXeq l⁻¹) for the first time in Atlantic waters. The PST profile in G. catenatum was determined via high performance liquid chromatography with fluorescence detection (HPLC-FLD) and consisted mostly of sulfocarbamoyl (C1+2, B1) and decarbamoyl (dcSTX, dcGTX2+3, dcNEO) toxins. The observed profile was similar to that reported previously in G. catenatum blooms in this region before the 10-year hiatus. Sardines, planktivorous fish that ingest a large number of phytoplankton cells, were found to contain PSTs in the viscera, reaching a maximum of 531 μg STXeq kg⁻¹. PSTs were not detected in corresponding muscle or brain tissues. The PST profile characterized in sardine samples consisted of the same sulfocarbamoyl and decarbamoyl toxins found in the algal prey with minor differences in relative abundance of each toxin. Overall, the data suggest that significant biotransformation of PSTs does not occur in sardines. Therefore, planktivorous fish may be a good tracer for the occurrence of offshore G. catenatum blooms and the associated PSTs produced by these algae.     

Species resolution and global distribution of microreticulate dinoflagellate cysts

The distribution, abundance and morphology of microreticulatedinoflagellate cysts were examined from samples collected fromthe coastal waters of Australia, the Baltic Sea, Italy, HongKong and Uruguay. On the basis of a combination of size range,variation in microreticulate pattern, and cyst wall colour,the three microreticulate species Gymnodinium catenatum (36–62µm diameter), Gymnodinium nolleri (25–40 µm)and Gymnodinium microreticulatum (17–29 µm) couldbe distinguished. Only G. catenatum and G. microreticulatumwere found at Australian sites. Gymnodinium microreticulatumwas rare but widespread in sediments from Tasmania and temperateand tropical sites on mainland Australia, whereas G. catenatumwas restricted to the eastern coast of Tasmania, southern Victoria,Port Lincoln [South Australia (SA)] and the Hawkesbury Estuary[New South Wales (NSW)]. Significant variation in G. catenatummean cyst size was observed between sites, with mean diametersvarying from 40.1 µm (Hawkesbury River, NSW) to 52.3 µm(Port Lincoln, SA). Laboratory experiments suggest that cystsize may be predominantly a genetically determined, population-specificcharacter, rather than being influenced by environmental parameters.Using the species criteria refined from the dataset, existingreports of microreticulate cysts are re-examined, and the globaldistribution of microreticulate cyst species and the biogeographyof the toxic dinoflagellate G. catenatum are re-evaluated.     

Palynological record (1483–1994) of Gymnodinium catenatum in Pescadero Basin, southern Gulf of California, Mexico

This paper presents the stratigraphic record of Gymnodinium catenatum during the last ~ 500 years, in Pescadero Basin, southern Gulf of California. Our aim is to help clarify the relation between abundances of cysts of G. catenatum and regional changes in the sea surface temperature and nutrient availability at a decadal scale. The record was obtained from core samples of laminated sediments dated with ¹⁴C, representing conditions in the area from 1483 to 1967 (PCM99-74C-5) and from 1907 to 1994 (PCM00-61C-4). Samples were treated with normal palynological processing, without oxidation, and using Lycopodium spores for quantification. The palynological assemblages observed contain varied and abundant terrestrial and marine components. However, we focus on the abundance of G. catenatum, due to its toxicity and the resulting impact in the area. This species is currently common in the area, and according to our results has been present there since ~ 1483. Cysts of G. catenatum are generally abundant in the 20th century, with maximum concentrations observed from 1888 to 1920, and from 1945 to 1965, but they show a steady decrease in the latter part of the century (1965–1994). Before 1830, abundances of G. catenatum were low because of increased upwelling conditions, probably related to a higher variability of the winter sea surface temperatures in the area. Both our data in the 20th century and the actual reports in the area, indicate a close relation with sea surface temperature. From 1907 to 1994 cyst abundances seem to increase during cool La Niña conditions in the area, and decrease during warmer El Niño events. They also show an evident decrease in cyst abundance from 1970 to 1994, while the sea surface temperature in the area increased during the same period. This inverse relation is also indicated by the low abundances of G. catenatum observed during red tide events, combined with high sea surface temperatures in Mazatlan. Additionally, our results do not show any relation of G. catenatum blooms and anthropogenic activity in the area.     

Cyst and radionuclide evidence demonstrate historic Gymnodinium catenatum dinoflagellate populations in Manukau and Hokianga Harbours, New Zealand

Between May 2000 and February 2001, a major bloom of the toxic dinoflagellate Gymnodinium catenatum (a causative organism of Paralytic Shellfish Poisoning, PSP) affected over 1500 km of coastline of New Zealand’s North Island. As this was the first record of this species in New Zealand, we aimed to resolve whether this represented a recent introduction/spreading event or perhaps an indigenous cryptic species stimulated by environmental/climatic change. To answer this question, we analysed for G. catenatum resting cysts in ²¹⁰Pb dated sediment cores (18–34 cm long; sedimentation rates 0.34–0.69 cm per year) collected by SCUBA divers from Manukau Harbour, where the species was first detected, and from Hokianga Harbour, where the highest shellfish toxicity was recorded, while using Wellington Harbour as a well-monitored control site. The results of this study conclusively demonstrate that abundant G. catenatum has been in northern New Zealand at least since the early 1980s, increasing up to 1200 cysts/g around the year 2000, but with low cyst concentrations possibly present since at least 1937. In contrast, Wellington Harbour cores contained only very sparse G. catenatum cysts (8 cysts/g), present only to a depth of 7 cm (surface mixed layer depth), reflecting an apparent recent range expansion of this dinoflagellate in New Zealand, possibly stimulated by unusual climatic conditions associated with the 2000 La Nina event. The significant increases since the early 1980s also of Protoperidinium cysts at Hokianga Harbour and of Gonyaulax, Protoperidinium and Protoceratium cysts at Manukau Harbour suggest a broad scale environmental change has occurred in Northland, New Zealand.     

Development and Evaluation of a PCR Based Assay for Detection of the Toxic Dinoflagellate, <Emphasis Type="Italic">Gymnodinium catenatum</Emphasis>(Graham) in Ballast Water and Environmental Samples

Gymnodinium catenatum is a bloom forming dinoflagellate that has been known to cause paralytic shellfish poisoning (PSP) in humans. It is being reported with increased frequency around the world, with ballast water transport implicated as a primary vector that may have contributed to its global spread. Major limitations to monitoring and management of its spread are the inability for early, rapid, and accurate detection of G. catenatum in plankton samples. This study explored the feasibility of developing a PCR-based method for specific detection of G. catenatumin cultures and heterogeneous ballast water and environmental samples. Sequence comparison of the large sub unit (LSU) ribosomal DNA locus of several strains and species of dinoflagellates allowed the design of G. catenatum specific PCR primers that are flanked by conserved regions. Assay specificity was validated through screening a range of dinoflagellate cultures, including the morphologically similar and taxonomically closely related species G. nolleri. Amplification of the diagnostic PCR product from all the strains of G. catenatum but not from other species of dinoflagellates tested imply the species specificity of the assay. Sensitivity of the assay to detect cysts in ballast water samples was established by simulated spiked experiments. The assay could detect G. catenatum in all ‘blank’ plankton samples that were spiked with five or more cysts. The assay was used to test environmental samples collected from the Derwent river estuary, Tasmania. Based on the results we conclude that the assay may be utilized in large scale screening of environmental and ballast water samples.     

Effects of light and temperature on the attachment and development of <Emphasis Type="BoldItalic">Gloiopeltis tenax</Emphasis> and <Emphasis Type="BoldItalic">Gloiopeltis furcata</Emphasis> tetraspores

Two 60-day experiments were conducted to study the influence of photon flux density (PFD) and temperature on the attachment and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores. In the first experiment, tetraspores of the two Gloiopeltis species were incubated at five temperature ranges (8°C, 12°C, 16°C, 20°C, 24°C) under a constant PFD of 80 μmol photons m⁻² s⁻¹ with a photoperiod of 12:12. In a second experiment, tetraspores were incubated under five PFD gradients (30, 55, 80, 105, 130 μmol photons m⁻² s⁻¹) at a constant temperature of 16°C with a photoperiod of 12:12. Maximum density of attached tetraspores was observed at 16°C for both species. Maximum per cent of spore germinating into disc was recorded at 12–16°C for G. tenax and 8–12°C for G. furcata. Maximum per cent of discs producing erect axes for G. tenax and G. furcata were recorded at 24°C and 20°C, respectively. Light had no significant effect on tetraspore attachment and developing into disc, but it affected the growth, sprouting and survival of its discs. Under 30–55 μmol photons m⁻² s⁻¹, the discs of the two species of Gloiopeltis did not form thallus until the end of the experiment. Optimum PFD range for G. tenax discs was 80–105 μmol photons m⁻² s⁻¹, whilst it was 80–130 μmol photons m⁻² s⁻¹ for G. furcata. Results presented in this study are expected to assist the progress of artificial seeding of Gloiopeltis.     

Deep-sea parasitic nematodes of the genus <Emphasis Type="Italic">Trophomera</Emphasis> Rubtsov et Platonova, 1974 (Benthimermithidae) from the Equatorial Atlantic,with the descriptions of two new species

Nematode females of the genus Trophomera (Benthimermithidae) from the collection of the Smithsonian’s National Museum of Natural History (Washington, DC, USA) were examined. Nematodes were collected in different parts of the Western Atlantic (Hatteras Abyssal Plain, Brazil Basin, and Argentina Basin) from depths of 467–5,223 m. Two new species are described. Body length of T. americana sp. n. is 3,250–4,470 μm; posterior end conical with rounded tip; cephalic setae about 3–4 μm long; trophosome consisting of several longitudinal rows of large cells; ovaries reflected; mature eggs 35 μm in diameter. Body length of T. longiovaris sp. n. is 7,870–15,400 μm; posterior end conical with rounded tip; cephalic sensilla 7 μm long; mouth opening vestigial, present as very narrow apical pore; pharynx devoid of internal lumen and muscular envelope; midgut represents a trophosome without internal lumen; trophosomal cells arranged in 3–4 longitudinal rows; rectum and anus vestigial; female reproductive system didelphic, amphidelphic, very long, occupying about 0.8 total body length; ovaries telogonic, outstretched; oviducts very long, repeatedly folded across body axis; proximal parts of oviducts being than distal ones, uterus distinctly formed. New finds of two known species, T. arnauidi and T. marionensis, are also recorded and described.     

Paralytic shellfish toxin profile in strains of the dinoflagellate Gymnodinium catenatum Graham and the scallop Argopecten ventricosus G.B. Sowerby II from Bahía Concepción, Gulf of California, Mexico

Gymnodinium catenatum Graham is a paralytic shellfish poison (PSP) producer that was described for the first time from the Gulf of California in 1943. During the last decade, its distribution along the Mexican Pacific coastline has increased. In Bahía Concepción, a coastal lagoon on the western side of the Gulf of California, G. catenatum has been linked to significant PSP concentrations found in mollusks. In this study, we describe the saxitoxin profile of 16 strains of G. catenatum, and catarina scallops (Argopecten ventricosus) from Bahía Concepción. Toxins were analyzed by HPLC with post-column oxidation and fluorescence detection. The average toxicity of the G. catenatum strains was 26.0±6.0 pg and 28.0±18.0 pg STX eq/cell after 17 and 22 days of growth, respectively. Ten toxins were recorded, but only dcSTX, dcGTX2, dcGTX3, C1, and C2 were always present in all strains at both growth stages. Since toxin profiles in scallops were similar to the cultures, biotransformations are not significant in catarina scallop. NeoSTX, GTX2, GTX3, and B2 were present in some G. catenatum strains and their presence varied with the age of the culture. In scallop samples, dcSTX, dcGTX2, and dcGTX3 were the most abundant toxins, and from the C-toxin group, only C2 was found. This unique toxin profile can be used as a biomarker for this population, when compared with strains of G. catenatum from other geographic regions.     

In vitro regeneration in <Emphasis Type="Italic">Dierama erectum</Emphasis> Hilliard

The genus Dierama comprises plants with a potential to be developed as ornamentals. D. erectum seeds were decontaminated and germinated on 1/10th strength Murashige and Skoog (Physiol Plant 15:473–497, 1962) (MS) media without plant growth regulators or sucrose. In an experiment investigating the effects of 6-benzyladenine (BA), meta-Topolin (mT), kinetin (KIN) and zeatin (Z) with or without α-naphthaleneacetic acid (NAA), the highest shoot number per hypocotyl (4.20 ± 0.51) was obtained from MS medium supplemented with 1.0 μM Z after 8 weeks. This was followed by a combination of 2.0 μM KIN and 2.0 μM NAA with 3.67 ± 0.81 shoots per explant. BA treatments produced 3.20 ± 0.22 shoots per hypocotyl explant when 2.0 μM was combined with 1.0 μM NAA, while mT gave 3.09 ± 0.99 shoots per explant when 2.0 μM mT was combined with 2.0 μM NAA. Adventitious shoot regeneration was optimised when shoots were grown under a 16-h photoperiod at 100 μmol m⁻² s⁻¹ on MS medium supplemented with 1.0 μM BA. This resulted in an average of 12.73 ± 1.03 shoots per hypocotyl explant. Various concentrations of ancymidol, activated charcoal and sucrose did not promote in vitro corm formation of this species. Plants rooted successfully after 8 weeks on MS medium supplemented with 1.0 μM indole-3-butyric acid (IBA) and had an average root number of 2.73 ± 0.40. After 2 months of acclimatisation, plants had formed corms. The largest corms (of diameter 0.45 ± 0.03 cm) were produced in plants pre-treated with 0.5 μM IBA. The highest plant survival percentage of 73% was also associated with this treatment.     

Phylogenetic,Inter, and Intraspecific Sequence Analysis of <Emphasis Type="Italic">spo0A</Emphasis> Gene of the Genus <Emphasis Type="Italic">Geobacillus</Emphasis>

In this work, the variability of spo0A gene in the genus Geobacillus and applicability of this gene for the taxonomy within this genus were evaluated. The protein Spo0A is the master regulator of the endospore-forming process in the all endospore-forming bacteria. Geobacillus genus-specific primers GEOSPO were designed based on the sequences of Geobacillus spo0A gene available through the public databases. Inter and intraspecific variability of Geobacillus spo0A gene was determined after sequencing of the GEOSPO-PCR products. Geobacillus spo0A sequence analysis showed that three species—Geobacillus thermodenitrificans, G. stearothermophilus, and G. jurassicus—could be easily identified. Similarity between the sequences of these species and the other species were in the range of 83.3%–92.0%. In contrast, intraspecific similarity of G. thermodenitrificans and G. stearothermophilus was high—above 99.0%. Similarity of spo0A sequences of G. subterraneus–G. uzenensis species cluster also matched this interval. Intercluster similarity between G. lituanicus–G. thermoleovorans–G. kaustophilus–G. vulcani and G. thermocatenulatus–G. gargensis–G. caldoxylosilyticus–G. toebii–G. thermoglucosidasius species clusters, as well as interspecific similarity within these two clusters was in the range of the intraspecific similarity determined for G. thermodenitrificans and G. stearothermophilus. It was also determined that spo0A cannot be used as the phylogenetic marker for the genus Geobacillus.     

Susceptibility of <Emphasis Type="Italic">Candida</Emphasis> biofilms to histatin 5 and fluconazole

Candida-associated denture stomatitis has a high rate of recurrence. Candida biofilms formed on denture acrylic are more resistant to antifungals than planktonic yeasts. Histatins, a family of basic peptides secreted by the major salivary glands in humans, especially histatin 5, possess significant antifungal properties. We examined antifungal activities of histatin 5 against planktonic or biofilm Candida albicans and Candida glabrata. Candida biofilms were developed on poly(methyl methacrylate) discs and treated with histatin 5 (0.01–100 μM) or fluconazole (1–200 μM). The metabolic activity of the biofilms was measured by the XTT reduction assay. The fungicidal activity of histatin 5 against planktonic Candida was tested by microdilution plate assay. Biofilm and planktonic C. albicans GDH18, UTR-14 and 6122/06 were highly susceptible to histatin 5, with 50% RMA (concentration of the agent causing 50% reduction in the metabolic activity; biofilm) of 4.6 ± 2.2, 6.9 ± 3.7 and 1.7 ± 1.5 μM, and IC₅₀ (planktonic cells) of 3.0 ± 0.5, 2.6 ± 0.1 and 4.8 ± 0.5, respectively. Biofilms of C. glabrata GDH1407 and 6115/06 were less susceptible to histatin 5, with 50% RMA of 31.2 ± 4.8 and 62.5 ± 0.7 μM, respectively. Planktonic C. glabrata was insensitive to histatin 5 (IC₅₀ > 100 μM). Biofilm-associated Candida was highly resistant to fluconazole in the range 1–200 μM; e.g. at 100 μM only ~20% inhibition was observed for C. albicans, and ~30% inhibition for C. glabrata. These results indicate that histatin 5 exhibits antifungal activity against biofilms of C. albicans and C. glabrata developed on denture acrylic. C. glabrata is significantly less sensitive to histatin 5 than C. albicans.     

Relationship between the dinoflagellate cyst Spiniferites pachydermus and Gonyaulax ellegaardiae sp. nov. from Izmir Bay,Turkey, and molecular characterization

Here, we established the cyst‐motile stage relation‐ship for Spiniferites pachydermus through incubation of cysts with a characteristically microreticulate/perforate surface isolated from Izmir Bay in the eastern Aegean Sea of the eastern Mediterranean. The morphology of the motile stage was similar to Gonyaulax spinifera but had a different size, overhang, displacement and reticulations. Based on the distinct morphology of the cyst and morphological differences in motile cells, we assigned S. pachydermus from Izmir Bay to the new species Gonyaulax ellegaardiae. We elucidate the phylogenetic relationship of G. ellegaardiae through large and small subunit ribosomal DNA and show that it forms a clade with other species that belong to the G. spinifera complex.     

Effects of growth medium, temperature, salinity and seawater source on the growth of Gymnodinium catenatum (Dinophyceae) from Bahia Concepcion, Gulf of California, Mexico

Laboratory studies were performed to determine the effect oftemperature, salinity, seawater sources and culture media onthe vegetative growth of clonal cultures of Gymnodinium catenatumisolated from Bahía Concepción, Mexico. Theseisolates were heterothallic and isogamous. Exponential growthrates of G. catenatum in f/2 with different selenium concentrationsand soil extract and GSe media were moderate. Maximum cell yieldswere obtained in GSe and f/2 media with selenium (10^–8and 10^–7 M), while in f/2 medium with soil extract cellyields were considerably lower. The highest percentage of longchains was found in f/2 media supplied with selenium (10^–8M). The optimal temperature range for growth was 11.5–30°C,with the highest growth rates between 21 and 29°C. The rangeof salinity tolerated by G. catenatum changed with seawatersource. With seawater from Vineyard Sound (Massachusetts, USA),G. catenatum grew at salinities from 15 to 36, with an optimalgrowth rate obtained at salinities between 26 and 30. With seawaterfrom Bahía Concepción, this species toleratedsalinities from 25 to 40, with optimal growth at salinitiesbetween 28 and 38. Ecophysiological measurements reported hereare consistent with the environment of the bay, which has limitedinput of humic materials from runoff and high salinity and temperature.These data, when viewed with data from studies of globally distributedG. catenatum, demonstrate the ability of this species to livein a broad array of habitats.     

Three new <Emphasis Type="Italic">Tomentella</Emphasis> species from West Africa identified by anatomical and molecular data

We used a combination of molecular-phylogenetic inference of 82 ITS rDNA sequences and anatomical approach to describe three new west African thelephoroid species, namely Tomentella afrostuposa, T. guineensis and T. guinkoi. Anatomically, T. afrostuposa is reminiscent of T. stuposa with globose to broadly ellipsoid large basidiospores of 8–14 μm, long aculei of up to 3 μm and prominent apiculi of 2 μm width. Molecular-phylogenetically, it falls within the T. stuposa complex. However, T. afrostuposa deviates by at least 7.80–10.74% from T. stuposa in regard with the ITS rDNA sequences. Tomentella guineensis is characterised by long (up to 85 μm) utriform basidia, the presence of reniform basidiospores in lateral view (up to 9 μm) with aculei not exceeding 1 μm and a strong cyanescent reaction of the subhymenial hyphae and basidia in 2.5% KOH. It forms a sister species of the newly described species Tomentella maroana; however, deviating from the last species by at least 9.75–10.04%. The very short, inflated (up to 14 μm) and thick-walled septate (septa up to 1.5 μm) subhymenial hyphae combined with ellipsoid basidiospores (up to 8 μm) and short aculei not exceeding 0.5 μm characterise Tomentella guinkoi. Anatomically, T. guinkoi recalls T. ellisii. Genetic distance between both species ranges from 12.67 to 13.73% according to ITS rDNA sequences analyses. Tomentella guinkoi forms a sister species of the group composed of T. ellisii, T. hjortstamiana and T. pisoniae. Detailed anatomical comparisons between the newly described species and their close relatives are given.     

The importance and distinctiveness of small-sized phytoplankton in the Magellan Straits

The distribution of summer phytoplankton across the Straits of Magellan (SOM) was studied with the aims of tracing differences among the distinct subregions of the area and contributing to the knowledge of its biodiversity. Samples collected at 25 stations were observed and counted in light microscopy. Selected samples were observed with transmission electron microscopy. The main unifying feature of the phytoplankton in the SOM was the high abundance and numerical dominance of small-sized (<10 μm) eukaryotic species, among which coccoid cells of <3 μm size were predominant (56.2 ± 30.6 of the total phytoplankton abundance). They mostly belonged to the prasinophyte Pycnococcus provasolii, which was abundant (0.8–6,834 cells × 10³ ml⁻¹) at all stations with the exception of those in proximity to the Atlantic entrances, where it was not recorded. Small-sized (<3 and 3–5 μm) diatoms (Minidiscus trioculatus, Lennoxia faveolata and other undetermined centric species) attained high densities (<3,757 cells 10³ ml⁻¹) especially at stations of the Patagonian sectors, whereas microplanktonic diatoms were only found at the two entrances of the Straits. Dinoflagellates were constituted mainly by >10 μm forms in the Andean subregion and <10 μm naked species in the Patagonian subregion, contributing up to 75.9 and 41.8% of the total carbon in these two areas, respectively. In the Patagonian subregion, flagellates mainly constituted by <5 μm forms and by cryptomonads <10 μm comprised up to 53.9% of the total biomass. Several species identified in this study have never been reported in other investigations in the SOM, while others, including Pycnococcus provasolii and Lennoxia faveolata, have rarely been recorded elsewhere. Overall, the summer phytoplankton of the Straits does not resemble that of any other region of the world’s seas. Although some of the predominant species might have been overlooked elsewhere, their abundance and relative importance apparently constitute a distinctive feature of the SOM.     

Regulation of glucose-6-phosphate dehydrogenase by reversible phosphorylation in liver of a freeze tolerant frog

Glucose-6-phosphate dehydrogenase (G6PDH) and the pentose phosphate pathway play a key role in reductive biosynthesis and antioxidant defense, while diverting glucose from other cellular functions. G6PDH was isolated from liver of the wood frog, Rana sylvatica, a freeze tolerant species that uses glucose as a cryoprotectant. Analysis of kinetic parameters (K _m and V _max) of G6PDH showed a significant increase in K _m G6P (from 98.2 ± 3.8 to 121 ± 5.3 μM) and K _m NADP⁺ (from 65.5 ± 2.3 to 89.1 ± 4.8 μM) in frogs following freezing exposure, indicating lower affinity for G6PDH substrates in this state. Subsequent analyses indicated that differential phosphorylation of G6PDH between the two states was responsible for the altered kinetic properties. Thus, two differentially charged forms of G6PDH were resolved by DEAE ion-exchange chromatography and, compared with controls, the proportion of G6PDH activity in peak I decreased and in peak II increased in liver from frozen frogs. G6PDH in peak I had a K _m G6P of 94.1 ± 1.1 μM and K _m NADP⁺ of 61.2 ± 3.5 μM, whereas Peak II G6PDH showed higher values (K _m G6P was 172 ± 4.3 μM, K _m NADP⁺ was 98.2 ± 3.3 μM). G6PDH from each peak was incubated with ions and second messengers to stimulate the actions of protein kinases with results indicating that G6PDH can be phosphorylated by protein kinase G, protein kinase C, AMP-activated protein kinase, or calmodulin-dependent protein kinase. The data indicate that in control frogs, G6PDH is in a high phosphate form and displays a high substrate affinity, whereas in frozen frogs G6PDH is less phosphorylated, with lower substrate affinity.     

Systematic review of the genus <Emphasis Type="Italic">Bothrocara</Emphasis> Bean 1890 (Teleostei: Zoarcidae)

The systematics of the eelpout genus Bothrocara Bean 1890 is reviewed on the basis of 941 specimens. Eight mostly eurybathic, demersal species are recognized, distributed mainly along the continental slopes of the North and South Pacific oceans, with one species entering the South Atlantic. Distributions are: B. brunneum ranges from the Sea of Okhotsk to the Gulf of Panama at depths of 199–1,829 m; B. elongatum ranges from the Gulf of Panama to Chile at depths of 720–1,866 m; B. hollandi ranges from the Sea of Japan to the southeastern Bering Sea at depths of 150–1,980 m; B. molle ranges from the western Bering Sea to the South Atlantic at depths of 106–2,688 m; B. nyx is known only from the eastern Bering Sea at depths of 790–1,508 m; B. pusillum ranges from the northern Bering Sea to British Columbia, Canada, at depths of 55–642 m; B. tanakae is found along the northern coasts of Honshu and Hokkaido islands, Japan, at depths of 274–892 m; B. zestum ranges from the Izu Islands, Japan, and central Honshu, Japan, to the Gulf of Alaska at depths of 199–1,620 m (an unidentifiable specimen from off Taiwan may be B. zestum). The species are distinguished from one another mainly on the basis of head pore patterns, gill raker morphology, coloration and various meristic and morphometric values. A determination key to the species is provided.