Photosynthetic capacity in microalgae associated with Antarctic pack ice

Summary Previous studies of primary production in Antarctic seas have concluded that microalgae associated with sea ice make only a minor contribution to the carbon budget; however, production estimates for sea ice algae have been based almost exclusively on microalgae from nearshore fast ice. We measured biomass and rates of photosynthesis (at saturating irradiances) in microalgae collected from offshore pack ice during four cruises to the Weddell-Scotia Sea and the region west of the Antarctic Peninsula. Chlorophyll a concentrations in pack ice (0.089 to 260 g 1^-1) were as high as reported from fast ice. Photosynthetic rates typically ranged (median 75%) from 0.3 to 3.6 C g chl a ^-1 h^-1 (n=127; arithmetic mean = 1.7, S D =1.9). These photosynthetic capacities are approximately an order of magnitude greater than previously reported for fast ice microalgae, but are similar to rates reported for Antarctic phytoplankton. Because pack ice constitutes more than 90% of the ice cover in Antarctic seas and indigenous microalgae have a higher photosynthetic capacity than previously realized, we raise the question: has the importance of sea ice algae to primary product: on in the southern ocean been underestimated?     

Some observations on the diet and food selection ofDaphnia hyalina (Cladocera) in an eutrophic lake

Summary The food composition in the guts ofDaphnia hyalina was compared with the phytoplankton composition in the lake water on several dates during the year. The guts contained almost exclusively algae; detritus was not an important food item. ExceptOscillatoria agardhii, all large algal forms were generally avoided. On a whole,Scenedesmus was the most preferred taxon, but as numbers or biomass ingestedO. agardhii was more important. The filamentous blue-green algae>60 m (range: 60–1500 m) were strongly avoided byDaphnia. The observed size selective feeding is probably the result of limitations in their filtering apparatus rather than active selection.     

Seasonal change of seston size distribution and phytoplankton composition in bivalve pearl oyster Pinctada fucata martensii culture farm

Seasonal changes of seston were monitored in the pearl cultivation area of Uchiumi Bay, Ehime Prefecture, Japan where the pearl oyster Pinctada fucata martensii is cultivated. The concentrations of chlorophyll a and particulate carbon, nitrogen and phosphorus were measured and the community structure of the phytoplankton investigated between June 1997 and February 1999. The seston was divided into pico- (<2 m), nano- (2–20 m) and large (>20 m) size fractions. The dominant size fraction during the study period, <2 m (38.1–51.4%), is consumed by oyster larvae but is too small for the adult pearl oyster. During the summers of 1997 and 1998 Nitzschia spp. became dominant but is indigestible for the oyster which was thus subjected to food limitation. We suggest monitoring the composition of seston and phytoplankton >2 m for evaluation of the food environment of the pearl oyster.     

Influence of Triterpene Glycosides of the Holothurian Cucumaria japonica on Root Growth in Cucumis sativus L. Seedlings

We have shown that triterpene glycosides of the Far Eastern edible holothurian Cucumaria japonica (monosulfated subfractions A ₂ and A ₄, disulfated subfraction A ₆, trisulfated subfraction A ₇, and the total fraction of monosulfated glycosides including subfractions A ₀, A ₁, A ₂, and A ₄) inhibited growth of the main root of Cucumis sativus seedlings. Cucumariosides were arranged as follows according to their inhibitory activity: subfraction A ₂ (ED₅₀ = 53.1 ± 3.6 g/ml) > total fraction of monosulfated glycosides (ED₅₀ = 127.4 ± 5.8 g/ml) > subfraction A ₄ (ED₅₀ = 346.5 ± 15.2 g/ml) > subfraction A ₆ (ED₅₀ = 375.7 ± 17.2 g/ml) > subfraction A ₇ (ED₅₀ = 539.4 ± 11.5 g/ml). The average length of the main root decreased with the increase of glycoside concentrations as a result of a growing amount of seedlings with low germination capacity and the absence of seedlings with high germination capacity.     

Food-chain relationships in subtidal silty sand marine sediments and the role of meiofauna in stimulating bacterial productivity

Summary From bibliographic data the biomass correlations (organic dry weight) are constructed for the subsurface layer of a hypothetical 30 m deep silty sand station: 200 g/ml macrofauna (including 120 g/ml subsurface deposit feeders), 50 g/ml meiofauna, 20 g/ml Foraminifera, 1 g/ml Ciliata and Flagellata, and 100 g/ml bacteria. ATP-biomass is discussed.Meiofauna and Foraminifera contribute with 30 and 12% to the living biomass in the sediment, and it is assumed that their contribution to the food of deposit-feeding macrofauna is of a similar percentage. This is corroborated by productivity estimations.Bacteria are the main food of deposit feeding macrofauna, meiofauna, and microfauna. From different calculations it becomes evident that the productivity of bacteria in the sediment is far below figures achieved in experimental cultures: the conclusion is that sediment bacteria, in general, do not live under good environmental conditions.A rather large part of the bacterial population in the sediment seems to be in the stationary phase of life, and only a fraction of the total population exhibits high metabolic rates and rapid duplications. Only these active bacteria are of importance for the breakdown of relatively refractive organic matter in the sediment.In soft bottom marine sediments where the input of organic matter is higher than the remineralization rate, benthic animals stimulate by their activities and by nutrient cycling the decomposition of detritus via bacteria. Though meiofauna, in principle, feeds upon the same food resource as macrofauna, there is no real competition for food, because meiofaunal animals by their activities and by excreting metabolic end products induce a bacterial productivity which would not be there without them, and feed on it. There are a few examples where more specialized interactions exist between benthic animals and bacteria; these interactions have been termed gardening. They could be highly important in the benthic ecosystem.     

Epizooic ciliates (Vorticella sp.) compete for food with their host Daphnia longispina in a small polyhumic lake

Summary Clearance rates of epizooic ciliates (Vorticella sp.) were measured together with their host, a planktonic cladoceran Daphnia longispina by using fluorescent latex beads as tracers of food. Vorticellans and their host graze on food of same size range (nanoplanktonic algae and bacteria). Individual clearance rates of Vorticella averaged 6.9 and 7.0 l ind^-1 h^-1 and those of Daphnia 463 and 708 l ind^-1 h^-1 for beads with diameter 2.00 and 3.92 m. On the average, epizooic vorticellans together on the carapace of Daphnia cleared particles with rates representing 25–33% of that the host cleared, the maximum rates being 50–80%. In a steeply stratified polyhumic lake vorticellans take advantage of following Daphnia to food patches and they can severely compete for food with their host.     

Effects of lead and cadmium on chemical composition and total water content of the pupal parasitoid, Pimpla turionellae

The parasitoid Pimpla turionellae L. (Hymenoptera, Ichneumonidae) was fed on Cd, Pb and Cd+Pb-contaminated food (33g Cd, 82g Pb and 33g Cd+82g Pb per gram food fresh weight, respectively). Significant decrease in the total lipid and protein content was found along with an increase in the water content particularly in Cd-contaminated parasitoids.     

Adventitious shoot formation from leaf explants of Rhododendron

A protocol for high frequency adventitious shoot regeneration adventitious shoot regeneration from leaf explants of Rhododendron spp. has been developed. The highest percentage of regeneration and the greatest number of shoots were obtained when leaf explants were cultured on Anderson's medium containing 4.9 M IBA and 73.8 M 2iP. Genotypic variation was observed for adventitious shoot regeneration potential among the seven cultivars tested. Regeneration frequencies ranged from 0 to 96%. Lodestar had the highest rate of regeneration after 3 months of culture with 96% shoot regeneration and an average of 14 shoots per explant. Regenerated shoots were rooted in soil in about 2 months. This protocol should be useful in applying gene transfer techniques to Rhododendron improvement.Abbreviations IAA 1-H-indole-3-acetic acid - NAA 1-naphthaleneacetic acid - IBA 1-H-indole-3-butyric acid - 2,4-d 2,4-dichlorophenoxyacetic acid - BA 6-benzyladenine - 2iP N-(3-methyl-2-butenyl)-1-H-purine-6-amine     

Das Cytostom von Lankesterella garnhami

Zusammenfassung Die Nahrungsaufnahme der Merozoiten von Lankesterella garnhami in den Milzzellen von Hamburger Hausspatzen (Passer d. domesticus) wurde elektronenmikroskopisch untersucht. Teile des Wirtszytoplasmas gelangen durch Abschnürung zahlreicher, etwa 20–30 m. großer Pinozytosevesikel in das Lumen der periparasitären Vakuole. Von dem Inhalt der periparasitären Vakuole werden Teile mit Hilfe mehrerer Cytostomstrukturen in Nahrungskanäle aufgenommen, von denen sich 100–200 m große Nahrungsvakuolen abschnüren, in denen die weitere Verdauung stattfindet. Das Cytostom ist durch zwei intensiv kontrastierte, konzentrische Zylinder charakterisiert, die sich von den beiden Pelliculamembranen ableiten. Der innere Durchmesser beträgt ca. 80m, der äußere Durchmesser ca. 150 m und die Tiefe im Ruhestadium mindestens 50–100 m. Die Bedeutung des Cytostoms als taxonomisches Merkmal wird diskutiert.

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The cytostome of Lankesterella garnhami

Summary The feeding mechanism of merozoites of Lankesterella garnhami in the cells of the spleen of young sparrows (Passer d. domesticus), which were captured in Hamburg, was studied by means of electron microscopy. The cytoplasm of the host cell permeates the membrane of the periparasitic vacuole by means of pinocytosis of vesicles with a diameter of 20–30 m. The parasite takes up parts of the content of the periparasitic vacuole with several cytostome structures. This structure consists of two electron dense, concentric cylinders, which originate from the two membranes of the pellicle. The cytostome is 80 m in the inner diameter and 150 m in the outer diameter. The depth of the inactive cytostomal cavity is about 50–100 m, whereas it is much prolonged in the stage of active feeding. In this stage the cytostome opens into a channel of 400–800 m and more, from which food vacuoles of 100–200 m are pinched off. Digestion occurs in the food vacuole. These findings are compared with observations of the cytostome and the micropyle in other sporozoa. Sometimes long, V-shaped invaginations of unknown signification are noticed.

     

In situ primary production in young Antarctic sea ice

An in situ incubation technique used successfully to measure the photosynthetic carbon assimilation of internal algal assemblages within thick multiyear Arctic ice was developed and improved to measure the photosynthetic carbon assimilation within young sea ice only 50 cm thick (Eastern Weddell Sea, Antarctica). The light transmission was improved by the construction of a cylindrical frame instead of using a transparent acrylic-glass barrel. The new device enabled some of the first precise measurements of in situ photosynthetic carbon assimilation in newly formed Antarctic sea ice, which is an important component in the sea ice ecosystem of the Antarctic Ocean. The rates of carbon assimilation of the interior algal assemblage (top to 5 cm from bottom) was 0.25 mg C m^–2 d^–1 whereas the bottom algal community (lowest 5 cm) attained only 0.02 mg C m^–2 d^–1. Chl a specific production rates (P^Chl) for bottom algae (0.020 – 0.056 g C g chl a ^–1 h^–1) revealed strong light limitation, whereas the interior algae (P^Chl = 0.7 – 1.2 g C g chl a ^–1 h^–1) were probably more limited by low temperatures (< –5 °C) and high brine salinities.     

Ice algae during EPOS,leg 1: assemblages,biomass, origin and nutrients

Summary Ice algae in infiltration assemblages were the dominating primary producers in the northwestern Weddell Sea during the austral spring 1988. Band and sub-ice assemblages were encountered at a few stations only. Maximum ice algal biomass measured was 424 g Chl. a I^–1 compared to less than 0.4, g Chl. a I^–1 in the water column. Biomass and nutrient concentrations in the infiltration layer decreased inward from the edge of ice floes. The composition of algal groups indicated that the concentric distribution was due to migration by mobile taxa. Various procedures for melting of ice-containing samples of algae were tested. Melting in dialysis tubing seemed to have advantages over other methods, especially for cells to be used in physiological experiments.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

The effects of Chilomonas on the life history traits of [-2pt] Daphnia longispina under semi-natural conditions and the implications for competition in the plankton

Assuming that heterotrophic flagellates (H.F.) can sustain cladoceran life cycles, particularly at periods of low food and high detritus conditions, the growth, reproduction and life span of Daphnia longispinawere studied under conditions of summer food limitation. They were fed both natural resources and natural food enriched with a culture of the colourless Chilomonas (ovoid cell, 8 × 25 m). Four H.F. morphotypes occurred in the natural water and the first experiments with Daphnia, showed that the cladoceran would most easily ingest those of 5 m–10 m, while the addition of Chilomonas severely depressed the H.F. of 2 m. The capability of this flagellate to ingest small H.F. was confirmed using fluorescent particles ranging from 0.94 to 3.95 m. As a consequence, Daphnia could control the abundance of H.F., but also compete with the largest morphotypes. To study the influence of the H.F. on the life span of Daphnia, the cladoceran was acclimated for two generations, before the start of the experiments. In semi-natural conditions, constant temperature, without predators and fed natural water, the summer daphnids achieved smaller sizes, produced fewer offspring and lived for a shorter time than when Chilomonas was added to their diet. Despite the addition of 560 g C l^-1, this was not sufficient to enhance the Daphnia reproduction to the level of the spring population fed natural water. These results clearly illustrate that the heterotrophic flagellates contributed significantly to improving the reproduction and survival of the daphnids. They emphasise the importance of the microbial loop as a link to larger consumers, particularly when unpalatable or nutritionally inadequate algae are dominant, which is often so in lakes during summer.     

In vitro sensitivity of environmental isolates of pathogenic dematiaceous fungi to azole compounds and a phenylpropyl-morpholine derivative

The in vitro sensitivity (minimum inhibitory concentrations; MICs) of 42 environmental isolates of pathogenic dematiaceous fungi to 7 azole compounds, viz. thiabendazole, ketoconazole, miconazole, econazole bifonazole, Bay n 7133, Bay 1 9139 and phenylpropyl-morpholine derivative, R_o14-4767/002 was studied by an agar dilution method using Emmon's Sabouraud dextrose agar (ESDA) as the culture medium.The isolates of Fonsecaea pedrosoi, Cladosporium carrionii, Exophiala jeanselmei and Ramichloridium subulatum were most sensitive to bifonazole with mean MICs of 0.06 g/ml or less; Phialophora verrucosa had an MIC of 0.05 g/ml to ketoconazola and R_o14-4767/002, respectively. Ochroconis sp had an MIC of 0.025 g/ml to R_o14-4767/002 and Cladosporium tennuisimum 0.39 g/ml to ketoconazole. Econazole and thiabendazole also showed good antifungal activity. The fungi were relatively resistant to the more recently developed azoles, viz. Bay n 7133 and Bay 1 9139, the later failing to inhibit C. tennuisimum at a concentration of 100 g/ml. The minimum fungicidal concentrations (MFC) of the drugs wree mostly within 2 to 8 fold of the MICs.     

Development of an L6 myoblast in vitro model of moniliformin toxicosis

L6 myoblasts were used as an in vitro model to investigate the role of moniliformin and its interaction with monensin in turkey knockdown syndrome and sudden death syndromes in poultry. Cell viability and microscopic and ultrastructural alterations noted in L6 myoblasts cultured in the presence of moniliformin (0.0–0.3 g/l) were compared to those observed in parallel cultures also containing one of the following compounds: selenium (0–0.004 ng/l), thiamine (0–0.3 g/l), or pyruvate (0–0.46 g/l). Marked dilation of the RER, membranous whorls, glycogen deposition, membrane-bound cytoplasmic inclusions and necrosis were observed in myoblasts exposed to 0.03/2-0.30 g moniliformin/l medium. Supplementation of medium with thiamine and pyruvate, or selenium, provided significant protection to cells exposed to 0.0–0.3 g/l or 0.0–0.15 g moniliformin/l, respectively. Dose-dependent differences in protein and ATP production were not detected. Myoblasts grown in medium containing 0–0.15 g moniliformin/l and 7.5–50.0 M A23187, beauvericin or monensin had degrees of cytotoxicity similar to parallel cultures receiving only an ionophore. L6 myoblasts were a useful model of moniliformin toxicosis. The findings of this study suggest cytotoxicity due to moniliformin in L6 myoblasts may be due in part to oxidative damage and altered pyruvate metabolism, and that moniliformin does not predispose myoblasts to ionophore toxicosis. This study supports the results of in vivo investigations in poultry that moniliformin and monensin do not act synergistically to induce knockdown or monensin toxicosis.     

Chlamydosporol,a new metabolite from Fusarium chlamydosporum

Extracts of rice on which an isolate of Fusarium chlamydosporum had been cultured were toxic to brine shrimps. The toxic fraction was purified by flash chromatography to give two compounds which were identified by UV, IR, NMR and mass spectroscopy at the 6 and 6 isomers of 5-hydroxy-4-methoxy-6, 8a-dimethyl-6,7-dihydro-2H,8aH-pyrano[2,3-b]pyran-2-one. These lactones for which the name chlamydosporol is proposed have not been reported previously. When tested in brine shrimp and HeLa cell assays, the LC₅₀ concentration for a mixture of the isomers was approximately 400 g/ml in both systems.     

Distribution and toxicity of a new colonial Microcystis aeruginosa bloom in the San Francisco Bay Estuary,California

The first distribution, biomass and toxicity study of a newly established bloom of the colonial cyanobacteria Microcystis aeruginosa was conducted on October 15, 2003 in the upper San Francisco Bay Estuary. Microcystis aeruginosa was widely distributed throughout 180 km of waterways in the upper San Francisco Bay Estuary from freshwater to brackish water environments and contained hepatotoxic microcystins at all stations. Other cyanobacteria toxins were absent or only present in trace amounts. The composition of the microcystins among stations was similar and dominated by demethyl microcystin-LR followed by microcystin-LR. In situ toxicity computed for the >75 m cell diameter size fraction was well below the 1 g l^–1 advisory level set by the World Health Organization for water quality, but the toxicity of the full population is unknown. The toxicity may have been greater earlier in the year when biomass was visibly higher. Toxicity was highest at low water temperature, water transparency and salinity. Microcystins from the bloom entered the food web and were present in both total zooplankton and clam tissue. Initial laboratory feeding tests suggested the cyanobacteria was not consumed by the adult copepod Eurytemora affinis, an important fishery food source in the estuary.     

Differential immunostaining for substance P in Huntington's Diseased and normal spinal cord: significance of serial (optimal,supra-optimal and end-point) dilutions of primary anti-serum in comparing biological specimens

Summary Using immunocytochemistry (ICC), the number of immunoreaction products (IRPs) visualized for the peptide substance P (SP) appears reduced within the human spinal cord (also substantia nigra) taken at autopsy from cases diagnosed with Huntington's disease (HD) compared with the non-HD cases (Vacca 1983). The reductions of SR-IRPs become apparent in the HD specimens when primary anti-SP serum is applied to the tissue sections at supra-optimal dilutions; that is, dilutions greater than the optimal dilutions which visualize maximal numbers of SP-IRPs and concomitantly give maximal staining intensity. Curiously, the application of optimal dilutions to the HD and non-HD specimens visualizes equivalent numbers of SP-IRPs; therefore, the qualitative and quantitative differences between the specimens become masked. Applying supra-optimal dilutions of the anti-SP serum unmasks the difference, and also reveals different end-points for the immunostain deposited in each type of specimen. In both the HD and non-HD specimens, two sizes of SP-IRPs could be identified, large (3 m) and small (0.7 m). Presumably they mark two different categories of axons defined by caliber (e.g.; C-type and A ), or origin (e.g., sensory intrinsic, or supraspinal). Alternatively the large SP-IRPs label tangentially-cut or large axons and nerve terminals. In the present report, counts of the large and small SP-IRPs visualized in the HD and the non-HD specimens have been plotted against the serial dilutions (optimal, supra-optimal and endpoint) of the primary anti-SP serum used for ICC. The graphs which result, describe a titration curve characteristic for the large SP-IRPs in each specimen. Applying supra-optimal dilutions of the primary antibody, causes the numbers of large and small SP-IRPs to decrease differentially. The numerical decrease probably largely reflects the concentration of immunoreactive antigen in different anatomic or metabolic tissue compartments. Alternatively, or perhaps to a lesser degree, the small and large SP-IRPs represent cross-reacting components which have different staining end-points, and may have biological significance in HD. Criteria are given for the proper use of ICC, and have significance regarding the use of commercial kits especially for pathological diagnosis.     

In vitro activity of seven azole compounds against some clinical isolates of non-dermatophytic filamentous fungi and some dermatophytes

The in vitro activity of seven azole compounds viz clotrimozole, isoconazole, bifanazole, fluconazole oxyconazole, Bay n 7133 and Bay L 9139 was investigated against 47 clinical isolates of pathogenic non-dermatophytic filamentous fungi and dermatophytic fungi. The isolates included Hendersonula toruloidea-26, Scytalidium hyalinium-5, Scytalidium japonicum-1, Trichophyton rubrum-5, Trichophyton tonsurans-3, Trichophyton mentagrophytes var. mentagrophytes-4, Epidemophyton floccosum-2, Microporum gypseum-2 isolates. The drugs were significantly more active against the dermatophytes (MIC range 0.025–1.56 g/ml) than non-dermatophytes (MIC range 0.39–6.25 g/ml). Isoconazole showed more activity than the rest of the azole compound tested. Clotrimazole, fluconazole, oxyconazole, bifonazole were comparable in their inhibitory activity against both dermatophytes and non-dermatophytes. The azole derivatives, Bay n 7133 and Bay L 9139 showed higher MIC range i.e. gave a range of 0.39–1.56 g/ml for dermatophytes and 1.56–6.25 g/ml for non-dermatophytic filamentous fungi. The minimal fungicidal concentration (MFC) of all the drugs tested were mostly within 2–8 times their MIC values.     

Problems in estimating growth rates of marine phytoplankton from short-term14C assays

Growth rate estimates () of phytoplankton populations that were sampled from nitrogen-limited continuous cultures and then incubated for short durations in batch culture with added¹⁴C-HCO₃ ^– were significantly different than steady-state growth rates () for 3 of 5 marine phytoplankton species. Two diatoms,Thalassiosira weissflogii andChaetoceros simplex, displayed virtually identical growth rates (=) over a wide range of, whereas for a third diatom,Phaeodactylum tricornutum, was overestimated by an average of 40% compared to. In contrast, was underestimated by the¹⁴C technique for the two remaining species: up to 40% at a steady-state of 1.0 day^–1 for the chlorophyteDunaliella tertiolecta and up to 100% at of 1.4 day^–1 for the haptophytePavlova lutheri. For the latter two species the divergence between and appeared to increase with increasing steady-state. A simple model of labeled and total carbon flow between the aqueous phase and cellular biomass was constructed to demonstrate that respiration was negligible when=, but was significant when>. In the cases in which<, a rapid physiological alteration presumably took place once the steady state was disturbed and cells were placed in the incubation chambers, which perhaps was related to the nutritional state of the cultures at the time of sampling. Questions thus are raised regarding our ability to measure accurately primary productivity from shipboard experiments with confined samples of phytoplankton from nutrient-impoverished waters that probably are less hardy than the laboratory cultures used in these studies.     

Comparative structure of the gas-vacuoles of blue-green algae

Summary An investigation was made of 5 species of blue-green algae reported to contain gas-vacuoles. All organisms were grown and harvested under standard conditions. Gas-vacuoles were characterised as reddish structures which are destroyed by applying pressure. Using a simple direct preparation technique gascylinders were observed with the transmission electron microscope in gas-vacuolate cells. Gas-vacuoles were present in the strains of Anabaena flos-aquae, Gloeotrichia echinulata and Oscillatoria agardhii studied and absent from Microcystis aeruginosa and Nostoc linckia. The reddish, refractile central area of N. linckia and M. aeruginosa cells was tentatively identified as nucleoplasm. Gas-vacuoles are collections of gas-cylinders 70 m wide, which in A. flos-aquae and G. echinulata are clearly bounded by photosynthetic lamellae and associated with -granules. The presence of bounding photosynthetic lamellae in these species is suggested as a causal factor of the unusual optical properties of their gas-vacuoles. The range of lengths of gas-cylinders in G. echinulata and O. agardhii is from 100 m to 500 m and in A. flos-aquae it is from 100 m to 1300 m. The percentage of cell volume occupied by gas-vacuoles was estimated by direct measurement. In A. flos-aquae and G. echinulata it was 22%. In O. agardhii gas-cylinders were not clearly associated with photosynthetic lamellae and -granules and occupied 39% of cell volume. Gascylinder membranes showed reasonable preservation in KMnO₄ and excellent preservation in OsO₄. The widths of membranes after treatment with these two fixatives was 3 m and 2 m respectively.