Fecundity,reproduction, and growth of Moina macrocopa fed different algae

Three micro algae, Ankistrodesmus convolutus, Scenedesmus incrassatulus and Chlorella vulgaris, at three concentrations, were tested as diets for Moina macrocopa. Their effect on reproduction, fecundity, growth and survival was evaluated. All three algae satisfied the nutritional requirements of M. macrocopa, despite their difference in size. The best concentration, expressed in dry weight, was 5 mg l^–1 for all three. Time to first reproduction was 4 days with all diets. Average time between clutches was 33 hours, and maximum number of clutches was 12; the highest average number of offspring per brood was 27. The largest broods were the fourth to sixth, depending on the diet. Ephippium hatching depends on temperature, taking only 24 hours at 30 °C and 48 hours at 27 °C. This species could be an important test organism in aquatic bioassays, and a live food in aquaculture.     

Somatic and population growth in selected cladoceran and rotifer species offered the cyanobacterium it Microcystis aeruginosa as food

The ability of cladocerans and rotifers to utilise the cyanobacterium Microcystis aeruginosa was tested by comparing the somatic and population growth in cultures using Chlorella and Microcystis as food types. Five species of cladocerans (Ceriodaphnia cornuta, Scapholeberis kingi, Moina macrocopa, Daphnia carinata, Simocephalus vetulus) and two species of rotifers (Brachionus calyciflorus, Hexarthra mira) were used in this study. In order to exclude the possibility of poor utilisation of Microcystis due to mechanical interference, single cells of Microcystis, (obtained by sonicating large colonies) were also offered. Experiments were done at 20 °Cs and 30 °C . In all the treatments tested, the population growth rate per day of the cladocerans ranged from -0.715 to 0.612 and that of the rotifers from -1.15 to 0.781. While C. cornuta, S. kingi and S. vetulus could utilise Microcystis, M. macrocopa and D. carinata were extremely susceptible to its toxins. The ability of the cladoceran populations to grow on Microcystis single cells was not related to the body length or gut length alone but to their ratio. The toxic effects of Microcystis were mitigated at the higher temperature. A strain of C. cornuta, collected from a Microcystis-dominated lake, had a higher growth rate on the toxic cyanobacteria suggesting that the tolerance to Microcystis could be a heritable trait. Of the two rotifer species, only H. mira survived and reproduced in some treatments of Microcystis. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Benthic cyanobacterial, Microcoleus lyngbyaceus, blooms in shallow, inshore Puerto Rican Seagrass habitats, Caribbean sea

Biomass and cover of Microcoleus lyngbyaceus (Kützing) Crouan were monitored at inshore seagrass habitats in southwest Puerto Rico for 16 months. Substantial localized blooms with maximum cover of 100% and comprising >600 g/m² were encountered. Abundance of Microcoleus (biomass and percent cover) were not significantly correlated with either water temperature or water column nitrogen (as nitrate and nitrite concentrations). M. lyngbyaceus has locally been implicated as being detrimental to the seagrass Thalassia testudinum König which is supported by circumstantial evidence. Thalassia cover declined in permanent quadrats that were strongly impacted with Microcoleus.     

Evaluation of Microcystis as food for zooplankton in a eutrophic lake

Four experiments were conducted to evaluate Microcystis as food for zooplankton in Lake Kasumigaura, and the following results were obtained. (1) Moina micrura (Cladocera) showed little growth and no reproduction when the animal was reared with Microcystis cultured in the laboratory. The animal did not grow nor reproduce well when Chlorella was mixed with Microcystis as food. (2) Moina micrura assimilated Microcystis much less than Chlorella when the animal fed on single species of Microcystis or a mixture with Chlorella. (3) Microcystis collected from Lake Kasumigaura could not be utilized by Moina micrura even though the colonies were broken up into edible sizes. However, the alga turned into utilizable food when it was decomposed. (4) No inhibitors of Moina micrura population growth could be found in the non-filtered water of Lake Kasumigaura where Microcystis was blooming heavily. Decomposed Microcystis seemed to be utilized by zooplankton as an important food source in Lake Kasumigaura.     

Cysteine and serine protease-mediated proteolysis in body homogenate of a zooplankter, Moina macrocopa, is inhibited by the toxic cyanobacterium, Microcystis aeruginosa PCC7806

The paper describes the characterization of proteases in the whole body homogenate of Moina macrocopa, which can possibly be inhibited by the extracts of Microcystis aeruginosa PCC7806. With the use of oligopeptide substrates and specific inhibitors, we detected the activities of trypsin, chymotrypsin, elastase and cysteine protease. Cysteine protease, the predominant enzyme behind proteolysis of a natural substrate, casein, was partially purified by gel filtration. The substrate SDS-polyacrylamide gel electrophoresis of body homogenate revealed the presence of nine bands of proteases (17-72 kDa). The apparent molecular mass of an exclusive cysteine protease was 60 kDa, whereas of trypsin, it was 17-24 kDa. An extract of M. aeruginosa PCC7806 significantly inhibited the activities of trypsin, chymotrypsin and cysteine protease in M. macrocopa body homogenate at estimated IC(50) of 6- to 79-microg dry mass mL(-1). Upon fractionation by C-18 solid-phase extraction, 60% methanolic elute contained all the protease inhibitors, and these metabolites could be further separated by reverse-phase liquid chromatography. The metabolites inhibitory to M. macrocopa proteases also inhibited the corresponding class of proteases of mammalian/plant origin. The study suggests that protease inhibition may contribute to chemical interaction of cyanobacteria and crustacean zooplankton.     

Effect of temperature and light on the toxicity and growth of the blue-green alga Microcystis aeruginosa (UV-006)

The toxicity and growth of Microcystis aeruginosa (UV-006) from the Hartbeespoort Dam, South Africa were investigated at different temperatures and photon fluence rates under laboratory conditions. Cells harvested in late logarithmic growth phase were most toxic when grown at 20°C (LD₅₀) median lethal dose [IP, mouse]=25.4 mg kg^-1). Toxicity was markedly reduced at growth temperatures above 28° C. Fluence rate had a smaller effect on the toxicity of the cells, but toxicity tended to be less at the very low and high light fluences. Optimal conditions for growth did not coincide with those for toxin production. Well-aerated cultures of this isolate kept at pH 9.5 by CO₂ addition, a temperature of 20–24° C, a fluence rate of 145 mol photons m^-2 s^-1 and harvested in the late logarithmic growth phase yielded the maximum quantity of toxin.Abbreviation LD₅₀ median lethal dose An abstract of this work, presented as a poster at the IUBS symposium on toxins and lectins, held at the CSIR, Pretoria, South Africa during 1982 was published in S. Afr. J. Sci. 78, 375 (1982)     

Inhibition of Chlorella growth by the lipids of cyanobacterium Microcystis aeruginosa

The total lipids of the cyanobacterium Microcystis aeruginosa have been isolated and fractionated into its components. Of these lipid components, only the fatty acid-containing fraction inhibited the growth of the green alga Chlorella pyrenoidosa. The inhibitory activity appears to be due to linoleic and linolenic acids, which are both present in significants quantities. These acids may be the substances responsible for the reported toxicity of Microcystis aeruginosa to Chlorella.     

Growth inhibition of the cyanobacterium Spirulina (Arthrospira) platensis by 1.7 MHz ultrasonic irradiation

Ultrasonic waves of high frequency (1.7 MHz) and low intensity (0.6 W cm^–2) were employed to prevent cyanobacterial cells from growing fast and the effects of this growth inhibition were investigated. At least five minutes of ultrasonic irradiation was essential for effective inhibition. The growth rate of irradiated cells was reduced to 38.9% of the control during short-term culture. Longer exposure did not significantly enhance the inhibition. For a particular level of energy input, distributed ultrasonic exposure (more short intermittent exposures) was more effective in inhibiting growth than fewer, but longer exposures. For instance, the final biomass decreased to 30.1% of the control after ultrasonic irradiation for 4 minutes every 3 days, whereas it only decreased to 60% of the control with exposure for 12 minutes every 11 days. It is suggested that distributed ultrasonic irradiation is a practical method to prevent cyanobacterial cells from fast growth. A possible explanation for the inhibition is discussed in relation to cell structure, the absorption spectrum of intact cells, chlorophyll level and oxygen evolution.     

Potassium-induced inhibition of nitrogen and phosphorus metabolism as a strategy of controlling <Emphasis Type="Italic">Microcystis</Emphasis> blooms

To explore potassium toxicity in Microcystis sp., growth, chlorophyll a, carotenoid and phycocyanin content, uptake of nitrate, phosphate and ammonium and activities of the assimilatory enzymes nitrate reductase, alkaline phosphatase and glutamine synthetase (GS) were studied. Nitrate, phosphate, ammonium uptakes and chlorophyll a and phycocyanin contents decreased with increase in the concentration of potassium, but carotenoid content registered an increase at increasing potassium concentration. Alkaline phosphatase and GS activities followed the trend of inhibition of their respective nutrients, whereas nitrate and nitrate reductase showed negative correlation (p < 0.01). Potassium was found to inhibit the activities of all the assimilatory enzymes in a non-competitive manner. Inhibitions of these parameters support the view that potassium has the potential to regulate Microcystis blooms in an eco-friendly manner.     

Fatty acids as trophic markers of phytoplankton blooms in the Bahía Blanca estuary (Buenos Aires, Argentina) and in Trinity Bay (Newfoundland, Canada)

The fatty acid compositions of phytoplankton and major primary consumers were analyzed during the development of seasonal algal blooms in the Bahía Blanca estuary, situated on the southern coast of the province of Buenos Aires (Argentina), and Trinity Bay, at Sunnyside, on the eastern coast of Newfoundland (Canada). Primary consumers in the Bahía Blanca estuary were zooplankton dominated by the calanoid copepod Acartia tonsa. At Sunnyside, the primary consumers were the sea scallop Placopecten magellanicus, an ecological and economical important benthic bivalve. The study shows that in spite of obvious differences between the two environments and the analytical approaches employed in each case, the analyses of fatty acid biomarkers can provide relevant ecological information. The fatty acid composition of the lipids of Bahía Blanca phytoplankton (high concentrations of the fatty acids 14:0, 16:4ω1, and 20:5ω3) reflected the presence of diatoms as a major component throughout the bloom. Fatty acid markers of the post-bloom phytoplankton in Bahía Blanca indicated a decline of phytoplankton biomass, and a relatively high input of detritus and terrestrial plant materials to the particulate organic matter of the estuary. Linoleic acid (18:2ω6), a typical “terrestrial” fatty acid, was conspicuous in the lipids of the post-bloom particulate matter of the Bahía Blanca estuary; 18:2ω2 was subsequently incorporated into zooplankton lipids diatom markers were also prominent in the lipids of pre-bloom and bloom phytoplankton at Sunnyside; post-bloom phytoplankton showed higher proportions of 18:0, 18:1ω9, and 18:4ω3, characteristic and often major fatty acids of dinoflagellates. The fatty acids of the digestive gland of P. magellanicus reflected the fatty acid composition of the phytoplankton, whereas those of the adductor muscle were practically unaffected by the composition of the food. This organ-specific response of an animal to the fatty acid composition of the diet is examined in terms of different applications of the fatty acid marker concept.     

Behavioral changes and growth inhibition in last instar larvae of Heliothis zea induced by oral and topical application of precocene II

In diet choice tests, newly-ecdysed fifth instar Heliothis zea larvae randomly chose diet containing 4 mM precocene II or diet without precocene II but initially preferred to feed on diet without precocene II. After two days, however, they were found more frequently on diet containing precocene II. Nevertheless, larval growth and development were inhibited when forced to eat diet containing precocene II. Removal of the maxillae, the site of the primary gustatory receptors, did not prevent the growth inhibition caused by larval consumption of diet with precocene II. Topical treatments with precocene II also caused larval growth inhibition, and daily treatments were more detrimental to the larvae than a large single dose. Addition of methylenedioxyprecocene (6,7-methylenedioxy-2,2-dimethylchromene) to the diet did not reverse the observed larval growth inhibition and this compound was itself significantly toxic. These results indicate that larval growth and development are disrupted after precocene II ingestion, but not because of preingestive discrimination by olfaction and gustation.     

Combined influences of particulate and dissolved factors in the toxicity of Microcystis aeruginosa (NRC-SS-17) to the rotifer Brachionus calyciflorus

The rotifer Brachionus calyciflorus is subject to the combined influence of particulate and dissolved factors derived from the toxic cyanobacterium Microcystis aeruginosa. Toxicity manifests itself through reduction of cohort survivorship and probably though reduction of cohort reproduction. Toxic effects are seen only when there is a particulate food material available in suspension, either M. aeruginosa itself or another food type which may act as a carrier for a dissolved toxic factor. Regardless of exact mechanism, the presence of a toxic strain of this blue-green may lead to diminution of population growth of co-occurring rotifer populations.     

Seasonal variations of Microcystis populations in sediments of Lake Biwa, Japan

Seasonal variations of colony numbers of Microcystis aeruginosa(Kütz.) Kütz. and M. wesenbergii(Komárek) Komárek in N. V. Kondrat. in sediments of Lake Biwa were investigated over a period of 1 year. At two stations located in the shallow South Basin of Lake Biwa (ca. 4 m water depth), the colony number of Microcystisfluctuated seasonally. The number had a tendency to gradually decrease from winter to early summer, while it increased through mid-summer and autumn. Since the Microcystispopulation in sediment was rather small, intensive growth and accumulation in the water column should be important for the formation of Microcystisblooms in Lake Biwa. Microcystiscolonies in the sediment samples after June were observed to be floating in a counting chamber under a microscope. The observation suggests that the recruitment of Microcystis colonies into the water column mostly occurs in early summer. The number of Microcystiscolonies in the deep North Basin of Lake Biwa (70 – 90 m water depth) was larger than in the South Basin. Because the seasonal variation of colony numbers was not observed in the North Basin, and Microcystiscells do not have gas vesicles, these colonies will not return into the water column. The colonies isolated from the sediment of the North Basin were able to grow in cultured conditions, in the same way as those from the sediment of the South Basin. Therefore, Microcystiscolonies may survive for a long time under stable conditions of low temperature (ca. 8 °C) and darkness, in the sediment of the deep North Basin, accumulating gradually each year.     

Genetic diversity of Microcystis populations in a bloom and its relationship to the environmental factors in Qinhuai River, China

Cyanobacterial blooms, forming massive scum and various cyanotoxins, increasingly spread in a wide range of freshwater ecosystems. One heavy Microcystis bloom occurred in the entire Qinhuai River basin in 2010 summer for the first time. To determine the Microcystis populations and their spatial distributions along Qinhuai River, a molecular approach was applied by sequencing the DNA library based on the internal transcribed spacer sequences of 16-23S rRNA (ITS). The parsimony network (TCS) analysis showed that 9 groups were formed based on the main 24 genotypes, and each group was dominated by one highly represented root sequence. Marked changes in the composition and proportion of the Microcystis ITS genotype were detected from the upper to the lower reaches. The seed sources forming the bloom were probably located at 4 different locations. Furthermore, it was found that pH was the primary factor affecting the spatial distribution of the main genotype group among samples.     

Peroxidation of lipids and growth inhibition induced by UV-B irradiation

Cotyledons excised from dark-grown seedlings of cucumber (Cucumis sativus L.) were cultured in vitro under UV radiation at different wavelengths, obtained by passage of light through cut-off filters with different transmittance properties. Growth and the synthesis of chlorophyll (Chl) in cotyledons were inhibited and malondialdehyde was accumulated upon irradiation at wavelengths below 320 nm. Exogenous application of scavengers of free radicals reversed the growth inhibition induced by UV-B. Measurement of the fluorescence of Chl a suggested that electron transfer in photosystems was affected by UV-B irradiation. On the basis of these results, the involvement is postulated of active species of oxygen in damages to thylakoid membranes and the growth inhibition that are induced by UV-B irradiation.Abbreviations Chl chlorophyll - F_m maximal fluorescence (dark) - F_m maximal fluorescence (light) - F_v variable fluorescence (dark) - F_v variable fluorescence (light) - MDA malondialdehyde - O₂ Superoxide radical - PS photosystem - q_N non-photochemical quenching of fluorescence - q_P photochemical quenching of fluorescence - UV-B_BE biologically effective UV-B radiation - WL(T = 0.5) wavelength at which 50% transmittance occurs     

Production of a thermophilic,extracellular alkaline protease by Bacillus stearothermophilus AP-4

A thermophilic Bacillus stearothermophilus strain AP-4 excreting a thermostable alkaline protease, was isolated from a local compost. Maximum activity of protease (250 U/ml) was after 36 h growth in broth at pH 9.0 and at 55°C. The protease was optimally active at pH 9.0 and 55°C and was stable in 5 mm CaCl₂. The enzyme was completely inactivated by PMSF, EDTA and -mercaptoethanol. It is therefore a metal ion-dependent, alkaline, serine protease.R. Dhandapani and R. Vijayaragavan are with the Centre for Plant Molecular Biology & Biotechnology, Tamil Nadu Agricultural University, Coimbatore 641 003, India     

First occurrence of Cochlodinium blooms in Sabah, Malaysia

Harmful algal blooms (HABs) resulting in red discoloration of coastal waters in Sepanggar Bay, off Kota Kinabalu, Sabah, East Malaysia, were first observed in January 2005. The species responsible for the bloom, which was identified as Cochlodinium polykrikoides, coincided with fish mortalities in cage-cultures. Determinations of cell density between January 2005 and June 2006 showed two peaks that occurred in March–June 2005 and June 2006. Cell abundance reached a maximum value of 6 × 10⁶ cells L⁻¹ at the fish cage sampling station where the water quality was characterized by high NO₃–N and PO₄–P concentrations. These blooms persisted into August 2005, were not detected during the north–east monsoon season and occurred again in May 2006. Favorable temperature, salinity and nutrient concentrations, which were similar to those associated with other C. polykrikoides blooms in the Asia Pacific region, likely promoted the growth of this species. Identification of C. polykrikoides as the causative organism was based on light and scanning microscopy, and confirmed by partial 18S ribosomal DNA sequences of two strains isolated during the bloom event (GenBank accession numbers DQ915169 and DQ915170).     

Toxic blooms of cyanobacteria in the Patos Lagoon Estuary,southern Brazil

The Patos Lagoon is the largest lagoonal system in South America. Its waters are formed by a huge drainage basin (201,600 km²) situated in the most industrialized areas of the Southern state of Rio Grande do Sul. On its margins more than 3 million inhabitants live in several cities and towns. The lagoon waters are used for leisure, drinking, industry, fisheries, agriculture and navigation. A monitoring and sampling program was developed from February 1994 to January 1996 with emphasis on the estuarine area, aiming to evaluate the occurrence of algal blooms. In the last 15 years, several cyanobacterial (blue-green algal) blooms of theMicrocystis aeruginosa have been registered in the lagoon estuary. HighM. aeruginosa biomass (50 to 9,000 g chla l^–1) was observed in the whole region in late summer and autumn 1994, and early summer 1995. The LD50 of toxic bloom samples tested in mice varied from 22 to 250 mg dry weight kg body weight^–1 while levels of toxicity (LC50) in the brine shrimp varied from 0.47 to 2.44 mg ml^–1. Toxicity varied in different blooms, in the distances along the scum and with time, within the same bloom. The hepatotoxin microcystin-LR was identified in almost all samples.     

Larval growth inhibition of the spiny bollworm,Earias insulana, by some steroidal secondary plant compounds

The effect of 23 secondary plant compounds including a series of steroidal aglycones and glycosides, on larval growth and pupation ofEarias insulana (Boisd.) was investigated. Larvae did not develop when fed on artificial diets containing 0.2% solamargine, solasonine, tomatine, digitonin, saponin, nomilin, lawsone or coumarin. Some growth-retarding activity was found with diets containing 0.2% ajmalicine, capsaicin, quercetin, glycyrrhizin and glycerrhetic acid. The eight compounds highly active at 0.2% were also bioassayed at 0.1, 0.05 and 0.01%: larvae did not pupate when fed on diets containing 0.1% solasonine, tomatine or nomilin, whereas solamargine and coumarin were active even at 0.05%. Preliminary structure-activity relationships were evaluated for the active steroidal glycosides.

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Larvale Wachstumshemmung des ägyptischen Baumwollkapselwurms, Earias insulana,durch einige steroide sekundäre Planzeninhaltstoffe

Zusammenfassung Es wurde die Wirkung von 23, einem künstlichen Nährmedium einverleibten, sekundären Pflanzeninhaltstoffen, unter ihnen eine Reihe steroider Aglucone und Glycoside, auf das Larvenwachstum und die Verpuppung vonEarias insulana untersucht. Larven entwickelten sich nicht in mit 0.2% Solamargin, Solasonin, Tomatin, Digitonin, Saponin, Nomilin, Lawsone und Coumarin versetzten Nährmedien. Auf Medien, die 0.2% Ajmalicin, Capsaicin, Quercetin, Glycyrrhizin and Glycyrrhetinsäure enhielten, war das Larvenwachstum verzögert. Die 8 bei 0.2% hoch wirksamen·Substanzen wurden auch bei 0.1, 0.05 und 0.01% getestet. Die Larven verpupten sich nicht auf 0.1% Solasonin, Tomatin und Nomilin und auf 0.05% Solamargin und Coumarin. Vorläufige Struktur-Wirksamkeit-Beziehungen wurden für die aktiven steroiden Glycoside vorgeschlagen.