Tolerance of ciliated protozoan Paramecium bursaria （Protozoa,Ciliophora） to ammonia and nitrites

The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in order to determine the lethal concentrations. Linear regression analysis revealed that the 2h-LC50 value for ammonia was 95.94 mg/L and for nitrite 27.35 mg/L using probit scale method (with 95% confidence intervals). There was a linear correlation between the mortality probit scale and logarithmic concentration of ammonia which fit by a regression equation y=7.32x-9.51 (R^2=0.98; y, mortality probit scale; x, logarithmic concentration of ammonia), by which 2 h-LC50 value for ammonia was found to be 95.50 mg/L. A linear correlation between mortality probit scales and logarithmic concentration of nitrite is also followed the regression equation y=2.86x 0.89 (R^2=0.95; y, mortality probit scale; x, logarithmic concentration of nitrite). The regression analysis of toxicity curves showed that the linear correlation between exposed time of ammonia-N LC50 valueand ammonia-N LC50 value followed the regression equation y=2 862.85e-0.08x (R^2=0.95; y, duration of exposure to LC50 value; x, LC50 value), and that between exposed time of nitrite-N LC50 value and nitrite-N LC50 value followed the regression equation y = 127.15e-0.13x (R^2=0.91; y, exposed time of LC50 value; x, LC50 value). The results demonstrate that the tolerance to ammonia in P. bursaria is considerably higher than that of the larvae or juveniles of some metozoa, e.g. cultured prawns and oysters. In addition, ciliates, as bacterial predators, are likely to play a positive role in maintaining and improving water quality in aquatic environments with high-level ammonium, such as sewage treatment systems.     

Effects of heavy metals （Pb^2＋ and Cd^2＋） on the ultrastructure, growth and pigment contents of the unicellular cyanobacterium Synechocystis sp. PCC 6803

The unicellular cyanobacterium Synechocystis sp. PCC 6803, a model organism known for its unique combination of highly desirable molecular genetic, physiological and morphological characteristics, was employed in the present study. The species was cultured in BG11 liquid medium contained various initial concentrations of Pb²⁺ and Cd²⁺ (0, 0.5, 1, 2, 4, 6 and 8 mg/L). The experiment was conducted for six days and the metal induced alterations in the ultrastructure, growth and pigment contents were assessed. Alterations in the ultrastructure of the Synechocystis sp. PCC 6803 cells became evident with the increased (>4 mg/L Pb²⁺) metal concentration. The photosynthetic apparatus (thylakoid membranes) were found to be the worst affected. Deteriorated or completely destroyed thylakoid membranes have made large empty spaces in the cell interior. In addition, at the highest concentration (8 mg/L Pb²⁺), the polyphosphate granules became more prominent both in size and number. Despite the initial slight stimulations (0.2, 3.8 and 6.5% respectively at 0.5, 1 and 2 mg/L Pb²⁺), both metals inhibited the growth in a dose-dependent manner as incubation progressed. Pigment contents (chlorophyll α, β carotene and phycocyanin) were also decreased with increasing metal concentration. Cells exposed to 6 mg/L Pb²⁺, resulted in 36.56, 37.39 and 29.34% reductions of chlorophyll α, β carotene and phycocyanin respectively over the control. Corresponding reductions for the same Cd²⁺concentrations were 57.83, 48.94 and 56.90%. Lethal concentration (96 h LC₅₀) values (3.47 mg/L Cd²⁺ and 12.11 mg/L Pb²⁺) indicated that Synechocystis sp. PCC 6803 is more vulnerable to Cd²⁺ than Pb²⁺. Supported by the Chinese Scholarship Council     

Mercury (Hg2+) effect on enzyme activities and hepatopancreas histostructures of juvenile Chinese mitten crab Eriocheir sinensis

We studied the effects of mercury (Hg²⁺) on antioxidant and digestive enzyme activities in terms of LC₅₀ value and on hepatopancreas histostructures of juvenile Chinese mitten crabs Eriocheir sinensis in 40-day exposure to various concentrations of Hg²⁺ (0, 0.01, 0.05, 0.10, 0.20, and 0.30 mg/L). The results show that the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) significantly increased in the concentrations of 0.01 and 0.05 mg/L, while that of enzyme decreased in 0.10, 0.20 and 0.30 mg/L treatments. Meanwhile, Hg²⁺ disrupted the histostructures of the hepatopancreas, causing decreases in activities of pepsin, tryptase, amylase, and cellulose, which are synthesized in the hepatopancreas. Moreover, as the Hg²⁺ concentration increased, the survival rate of the crabs decreased, worst at 56.57% in 0.30 mg/L. Therefore, although crabs are able to tolerate low levels of mercury pollution, high levels lead to cellular injury and tissue damage in hepatopancreas, which then loses some of its vital physiological functions such as absorption, storage, and secretion.     

Laboratory study on the ecological impact of sophorolipid used for harmful algae elimination

We studied the role of sophorolipid in inhibiting harmful algae bloom (HAB). Different sophorolipid concentrations were tested on marine microalgae, zooplankton, fish, and bivalve (Mytilus edulis) in laboratory. The result shows that sophorolipid could inhibit the growth of algal species selectively. Among three algae species selected, Platymonas helgolandica var. tsingtaoensis was promoted with increasing sophorolipid concentration; Isochrysis galbana was inhibited seven days later in sophorolipid concentration below 40 mg/L; and Nitzschia closterium f. minutissima was inhibited obviously in only a high sophorolipid concentration over 20 mg/L. Therefore, sophorolipid in a low concentration at <20 mg/L could remove certain harmful algae species effectively without harming other non-harmful microalgae. For other animals, sophorolipid could inhibit the growth of ciliate Strombidium sp. by 50% at 20 mg/L sophorolipid concentration after 96 h. The concentration in 96-h LC₅₀ for Calanus sinicus, Neomysis awatschensis, Lateolabrax japonicus, and Paralichthys olivaceus was 15, 150, 60, and 110 mg/L, respectively. The 24 h LC₅₀ value for Artemia salina was 600 mg/L. The relative clearance rate of mussel Mytilus edulis decreased to 80%, 40%, and 20% of the control group after being exposed to 20, 50, and 100 mg/L sophorolipid for 24 h. Therefore, the toxicity for mitigation of harmful algae bloom at previously recommended concentration of 5–20 mg/L sophorolipid is low for most tested organisms in this reaserch.     

Toxic effects of Zn2+, Cu2+, Cd2+ and NH3 on Chinese prawn

This study deals with the toxic effects of Zn²⁺, Cu²⁺, Cd²⁺ and NH₃ on Chinese prawn (Penaeus orientalis). The median lethal concentrations of the toxic matters on Chinese prawn were determined. Cd²⁺>Cu²⁺>Zn²⁺>NH₃-Nm is the toxic order of these chemicals to Chinese prawn. The toxic order of concentrated Zn²⁺ and Cd²⁺ in tissues and organs of Chinese prawn is in the order. gill>shell+appendage>viscera>muscle.     

Bioaccumulation of Pb<Superscript>2+</Superscript> and its effects on growth,morphology and pigment contents of <Emphasis Type="Italic">Spirulina</Emphasis> (<Emphasis Type="Italic">Arthrospira</Emphasis>) <Emphasis Type="Italic">platensis</Emphasis>

A laboratory experiment was conducted to assess the bioaccumulation of Pb²⁺ and its effects on growth, morphology and pigment contents of Spirulina (Arthrospira) platensis. The specimen cultured in Zarrouk liquid medium was treated with various initial metal concentrations (0, 5, 10, 30, 50 and 100 μg mL⁻¹). The growth of S. platensis was adversely affected by Pb²⁺ at high concentrations (30, 50 and 100 μg mL⁻¹). However, at low concentrations (5 μg mL⁻¹), Pb²⁺ could stimulate its growth slightly. The pigment contents (chlorophyll α and β carotene) were decreased in a dose-dependent manner. The highest reductions (67% and 53% respectively in chlorophyll α and β carotene) were observed in 100 μg mL⁻¹ treatment group. The LC₅₀ (96 h) of Pb²⁺ was measured as 75.34 μg mL⁻¹. Apart from a few cases of filament breakages at elevated concentrations (50 and 100 μg mL⁻¹), morphological abnormalities are not specific. Metal bioaccumulation increased with Pb²⁺ concentrations, but decreased with exposure time. The maximum accumulated amount was 188 mg g⁻¹ dry weight. The bioconcentration factor (BCF) reached to a peak at day 2, followed by a gradual reduction for all the exposure concentrations. S. platensis is able to tolerate considerably high Pb²⁺ concentrations. Consequently it can be used as a potential species to remove heavy metal from contaminated waters.     

Variations of antioxidant enzyme activity and malondialdehyde content in nemertean Cephalothrix hongkongiensis after exposure to heavy metals

The antioxidant enzyme activity and malondialdehyde (MDA) content of Cephalothrix hongkongiensis were studied to assess variations in the biochemical/physiological parameters of nemerteans under heavy metal stress. Worms were exposed to copper, zinc and cadmium solutions at different concentrations, and the activity of three antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX), and MDA content were measured. The results show that the activity of each enzyme changed immediately after exposure to heavy metals. CAT was invariably inhibited throughout the experimental period, while the SOD activity was significantly elevated by exposure to Cu²⁺ for 48 h, but then decreased. SOD was inhibited by Zn²⁺during the first 12 h of exposure, but activated when exposed for longer periods. Under Cd²⁺ stress, SOD activity decreased within 72 h. GPX activity varied greatly, being significantly increased by both Cu²⁺ and Zn²⁺, but significantly inhibited by Cd²⁺ in the first 12–24 h after exposure. MDA content increased on Cu²⁺ exposure, but normally decreased on Zn²⁺ exposure. MDA content followed an increase-decrease-increase pattern under Cd²⁺ stress. In conclusion, the antioxidant system of this nemertean is sensitive to heavy metals, and its CAT activity may be a potential biomarker for monitoring heavy metal levels in the environment.     

Acute toxicity and biodegradation of endosulfan by the polychaeta Perinereis aibuhitensis in an indoor culture

The polychaete Perinereis aibuhitensis, a key species in estuarine ecosystems, can improve the culture condition of sediment. Endosulfan is an organochlorine pesticide used globally to control insects and mites; however, it is a source of pollution in aquaculture as a result of runoff or accidental release. In this study, we evaluated the toxicity of endosulfan to polychaeta and its ability to improve polluted sediment. Specifically, the effects of a series of endosulfan concentrations (0, 1.25, 2.5, 5, 10, 15, and 20 mg/L) were investigated, and the results indicated that the 24-h median lethal concentration (24-h LC₅₀) was 55.57 mg/L, while the 48-h median lethal concentration (48-h LC₅₀) was 15.56 mg/L, and the safe concentration was about 1.556 mg/L. In a 30-d exposure experiment, the animal specimen could decompose endosulfan effectively while improving endosulfan-polluted aquatic sediment.     

Acute Toxicity of Formalin to the Red-tide Dinoflageilate Prorocentrum minimum Schiller （Protozoa, Mastigophora）

The acute toxic levels of formalin to a marine red-tide dinoflagellate Prorocentrum minimum Schiller (Mastigophora, Dinoflagellida) were determined by linear regression analysis. The data obtained revealed that there is a close regression relationship between logarithmic concentrations of formalin and mortality probit scales of the organism when exposure times are 1, 2, 6, 12, 24 h. The median lethal concentrations (LC50 values) obtained from correlation analysis for these exposure times (with 95% confidence intervals), were 11.83, 6.76, 4.37, 4.27 and 3.98mgL^-1 respectively. A toxicity curve was obtained to connect the exposure time and LC50 value from the correlation between them. The results indicated that P. minimum could be killed or fixed by formalin in the concentration range of 4-12mgL^-1 within 1-24h.     

Purification and characterization of novel κ-carrageenase from marine Tamlana sp. HC4

We isolated a bacterial strain (HC4) that is able to degrade κ-carrageenan from a live specimen of the red alga Hyalosiphonia caespitosa. With 16S rRNA gene sequencing, we identified the strain as Tamlana sp., and then purified an extracellular κ-carrageenase from a culture of Tamlana sp. HC4 by ammonium sulfate precipitation, Sephadex G-200 gel filtration chromatography, and DE-cellulose 52 anion-exchange chromatography. The purified enzyme yields a single band on SDS-PAGE with a molecular mass of 66.4 kDa. The optimal pH and temperature for κ-carrageenase activity are at 8.0 and 30°C, respectively. The enzyme is stable over the range of pH 7.2–8.6 below 45°C. The enzyme activity is strongly inhibited by Zn²⁺ and Cu²⁺ at 1 mmol/L. The enzyme-catalyzed reaction follows Michaelis-Menten kinetics with the Michaelis constant (K _m ) at 7.63 mg/ml. Analysis of the degradation products of the κ-carrageenase by ESI-MS and ¹³C-NMR spectroscopy indicates that the enzyme degrades κ-carrageenan down to the level of κ-neocarrabiose sulfate.     

Acute toxicity of organochlorine insecticide endosulfan to the giant freshwater prawn Macrobrochium rosenbergii

Endosulfan, an organochlorine pesticide, is highly toxic and effective at controlling pests in agriculture, horticulture, and public health programs. In this study, static bioassays were used to evaluate the toxicity of endosulfan to freshwater prawns( Macrobrachium rosenbergii) of various lengths(1.5±0.03,4±0.08, and 7±0.06 cm). Additionally, the activities of peroxidase(POD), acid phosphatase(ACP),alkaline phosphatase, acetylcholinesterase(AChE), and Na + /K +-ATPase were analyzed to refl ect the effects of endosulfan exposure. The 96 h LC 50 of endosulfan for prawns 1.5, 4, and 7 cm long were 1.86, 4.53,and 6.09μg/L, respectively, improved tolerance to endosulfan with growth. The POD activities of test organisms exposed to low concentrations of endosulfan were inhibited, indicating the presence of oxygen damaged tissue. Moreover, a notable decrease in AChE activity was observed due to overstimulation of neurotransmission, which might result in abnormal behavior. The effect caused by endosulfan on phosphatase production in the hepatopancreas of prawns 1.5, 4, and 7 cm long was different because the ability of nonspecifi c immune regulation increased with growth. The 96 h LC 50 values obtained in this study could be used in the formulation of water-quality criteria in China. Moreover, the changes in enzymes activities of M. rosenbergii under stress of endosulfan could be applied in the establishment of early warning indicators for bio-safety.     

Studies on culture conditions of benthic diatoms for feeding abalone

Effects of salinity, pH, nitrogenous and phosphate nutrients on the growth rate of four species of benthic diatoms were studied by using the method of in situ optical density measurement. The optimal culture conditions for the four species of diatoms are as follows: forAmphora coffeaeformis, s 35; pH 8.5; NO₃ ⁻−N 1.54, NH₄ ⁺−N, 7.0; CO (NH₂)₂−N, 2.5 (mg/L); PO₄ ³⁻−P 1.13 (mg/L); forCocconeis scutellum varparva, s 30; pH 8.5; NO ₃ ⁻ −N 3.08, NH ₄ ⁺ −N 3.5, CO(NH₂)₂−N 5.0 (mg/L); pO ₄ ³⁻ −P 0.283 (mg/L); forNavicula corymbosa s 25; pH 8.0; NO ₃ ⁻ −N 1.54, NH ₄ ⁺ −N 3.5 CO(NH₂)₂−N 5.0 (mg/L); PO ₄ ³⁻ −P 0.565 (mg/L); forNavicula mollis. s 25; pH 8.0; NO ₃ ⁻ −N 1.54, NH ₄ ⁺ −N 1.75, CO(NH₂)₂−N 1.25 (mg/L); PO ₄ ³⁻ −P 0.141 (mg/L). Part of the results of this paper were exchanged in the Fourth Asian Aquaculture Forum. Oct. 16–20. 1995. Beijing, P. R. China.     

Hyper-spectrum models for monitoring water quality in Dianshan Lake,China

The correlation between water quality parameters and hyper-spectral reflectance is studied with models established for each parameter and applied in Dianshan Lake, in the upstream of the Huangpu River running through Shanghai, China. Models are for dissolved oxygen (DO in mg/L): R720/R680 = 20.362×(R720/R680)2-31.438×(R720/R680)+19.156; for turbidity (NTU): R*714.5 = 206.07× (R*714.5)2-582.5×R*714.5 + 423.24; and for total phosphorus (TP in mg/L): R*509.5 = 16.661× (R*509.5)2-32.646×R*509.5+16.116. The R2 values are 0.770 8, 0.660 4 and 0.738 7, respectively, showing strong positive relationships. The models were then applied to assess water quality of different times. Results are quite satisfactory for some samples.     

The influence of Fe^2＋ on growth and development of cells enzymatically isolated from Porphyra yezoensis blades

Fe^2＋ acted as an accessorial factor for many cellular enzymatic reactions is very important for seaweed growth and development, but the Fe^2＋ requirement in nori had not been seen. Porphyra yezoensis cells were separated enzymatically and cultured in a series of sterilized seawater media containing various concentrations of Fe^2＋. The growth development and cell were investigated in this work. Through this experiment, two biologically-meant concentration scales were found, one is low concentrations, 12.1-102.1μg/L, 10-100 times than that in seawater, favoring the development of isolated cells of Porphyra and the other was high concentrations, more than 10mg/L inhibiting the cell growth, leading to the deformity and shrinkage of the cells. At the concentration of 50 mg/L, the cells stopped growing and died eventually.     

Effects of Mg2+, NaCl, citric acid, and other factors on synthesis and accumulation of β-carotene inDunaliella salina

The effect of Mg²⁺, NaCl and citric acid on the accumulation of β-carotene inDunaliella Salina was studied. The experimental results showed that 10.5 mmol/L Mg²⁺, 5 mol/L NaCl, 3 μmol/L citric acid, and CO₂ are favorable forDunaliella Salina cell growth and β-carotene accumulation. After 144 h culture under the above conditions, theDunaliella Salina biomass increased by 7.18 times; β-carotene reached 9.61%. Project 89023990 supported by the Shandong Natural Science Fund.     

Roles of polysaccharide from <Emphasis Type="Italic">Branchiostoma belcheri</Emphasis> in anti-DNA oxidation and anti-tumor activity in S180 mice

In this study, we isolated a polysaccharide from Branchiostoma belcheri (PBB) by enzymatic protein hydrolysis and alcohol precipitation. We investigated the effects of PBB supplementation on DNA oxidation and growth of the transplanted tumor cells Sarcoma (S₁₈₀) in mice. Sixty healthy Kunming mice weighing between 18 and 25 g were randomly assigned to 6 groups, each consisting of 10 animals. All the mice, except for the blank control group, were inoculated with S180 sarcoma cells into the axilla of the left foreleg. PBB was given to mice by gavage at doses of 0 (model control), 25, 50, or 100 mg/kg b.w. in 0.2 ml saline for 30 days. The fifth group of S₁₈₀-mice was given cytoxan (50 mg/kg) by peritoneal injection as a positive control group. The animals had free access to food and water. The mice were sacrificed after the final treatment and blood was quickly collected. Spontaneous and oxidized DNA damage of peripheral lymphocytes induced by H₂O₂ were analyzed by SCGE. O⁶-methyl-guanine (O⁶-MeG) was measured by high-performance capillary zone electrophoresis. The average tumor weights (0.856–1.118 g) of the three PBB groups were significantly lower than that of the model control group (1.836 g) (p<0.05). The tumor inhibition ratios of the PBB groups were 39.1%–53.4% and similar to the cytoxan positive group (57.5%). There were no significant differences in spontaneous DNA damage in peripheral lymphocytes among the groups. The oxidative DNA damage induced by 10 μmol/L H₂O₂ in the 50 and 100 mg/kg b.w. groups were 246.1 AU and 221.7 AU, respectively, both of which were significantly lower than that in the model group (289.0 AU; p<0.05). The plasma concentrations of O⁶-MeG in the 25, 50, and 100 mg/kg supplemented groups were 2.09 μmol/L, 1.86 μmol/L, and 1.63 μmol/L, respectively, all of which were significantly lower than that of the model group (2.67 μmol/L; p<0.05). These results indicated that PBB may have antioxidative activity and thus reduce oxidation-induced DNA damage.     

Toxicity of five phenolic compounds to brine shrimp Artemia sinica (Crustacea: Artemiidae)

The acute toxicity of five phenolic compounds each to 15 d old Artemia sinica was determined in this study. The brine shrimp A. sinica was hatched from the encysted dry eggs(Bohai Bay Brand) produced by Dongying Ocean Artemia Co., Ltd., China at 27℃± 1℃ in pre-filtered(through pores of 0.45 μm in diameter) and autoclaved seawater(salinity 31, pH 7.5–8.0) in a cilindroconical glass beaker(2000 mL in volume) under continuous illumination(provided by a side set 20 W fluorescent lamp) with slight aeration. Ten Artemia individuals from the same batch of the hatched were cultured in 10 mL toxicant solution prepared with seawater(salinity 31, pH 7.5–8.0) at room temperature(about 20℃) to determine 24 h, 48 h and 72 h medium lethal concentration(LC50) of 5 phenolic compounds each. It was found that the toxicity of n-heptylphenol was the highest followed by nonylphenol, t-butylphenol, 2,4-dichlorophenol and bisphenol A in order. The LC50 values of the 5 compounds were calculated with regression analysis. The real concentration(in μg- L1) of 5 phenolic compounds each in toxicant solutions was measured with GC/MS analysis. Significant loss of phenolic compounds caused by either adsorption or desorption was not found. The significant difference of LC50 values was found among the five compounds 3 exposure times each. The range between the highest no-observed-effect concentration(NOEC) and 100% death causing concentration of five phenolic compounds each was determined. The toxicity in term of 24 h LC50 value of n-HP was 9.10 times higher than that of BPA, 1.71 times higher than t-BP, 1.53 times higher than 2,4-DCP and 1.36 times higher than NP, respectively.     

Effects of iron electrovalence and species on growth and astaxanthin production of Haematococcus pluvialis

To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron electrovalencies (Fe²⁺-EDTA and Fe³⁺-EDTA) and species (Fe-EDTA, Fe(OH)_x^32x and FeC₆H₅O₇) addition on cell growth and accumulation of astaxanthin were studied. Results show that different iron electrovalencies have various effects on cell growth and astaxanthin accumulation of H. pluvialis. Compared with Fe³⁺-EDTA, Fe²⁺-EDTA stimulate more effectively the formation of astaxanthin. The maximum astaxanthin content (30.70 mg/g biomass cell) was obtained under conditions of 18 μmol/L Fe²⁺-EDTA, despite the lower cell density (2.3×10⁵ cell/ml) in such condition. Fe³⁺-EDTA is more effective than Fe²⁺-EDTA in improving the cell growth. Especially, the maximal steady-state cell density, 2.9×10⁵ cell/ml was obtained at 18 μmol/L Fe³⁺-EDTA addition. On the other hand, all the various species of iron (EDTA-Fe, Fe(OH)_x^32x, FeC₆H₅O₇) are capable to improve the growth of the algae and astaxanthin production. Among the three iron species, FeC₆H₅O₇ performed the best. Under the condition of a higher concentration (36 μmol/L) of FeC₆H₅O₇, the cell density and astaxanthin production is 2 and 7 times higher than those of iron-limited group, respectively. The present study demonstrates that the effects of the stimulation with different iron species increased in the order of FeC₆H₅O₇, Fe(OH)_x^32x and EDTA-Fe. Supported by Xiamen Scientific and Technologic Projects (No. 3052Z20031086), Xiamen University Alumni Association Foundation in Singapore, and the First National College Students Innovative Experimental Project     

Purification and characterization of cold-active endo-1,4-β-glucanase produced by Pseudoalteromonas sp. AN545 from Antarctica

A bacterium hydrolyzing carboxymethylcellulose, isolated from Antarctic sea ice, was identified as Pseudoalteromonas sp. based on 16S rDNA gene sequences and named as Pseudoalteromonas sp. AN545. The extracellular endo-1,4-β-glucanase AN-1 was purified successively by ammonium sulfate precipitation, DEAE-Sepharose ion exchange chromatography and Sephadex G-75 gel filtration chromatography. The molecular mass of AN-1 was estimated to be 47.5 kDa utilizing SDS-PAGE and gel chromatography analysis. AN-1 could hydrolyze caboxymethylcellulose, avicel and β-glucan, but not cellobiose, xylan and p-Nitrophenyl-β-D-glucopyranoside. The optimal temperature and pH for the β-glucanase activity of AN-1 were determined to be at 30°C and pH 6.0, respectively. AN-1 was stable at acidic solutions of pH 5.0-6.5 and temperatures below 30°C for 1 h. Moreover, the specific activity was enhanced by Ca2+ and Mg2+, and inhibited by Cu2+. The kinetic parameters Michaelis constant (Km) and maximum velocity (Vmax) of AN-1 were 3.96 mg/mL and 6.06×10-2 mg/(min·mL), respectively.     

Acute toxicities of potassium permanganate, formalin, and Lugol’s iodine solution to a marine ciliate, Pleuronema coronatum (ciliophora, scuticociliatida)

Acute toxicities of potassium permanganate, formalin, and Lugol’s iodine solution to a commonly occurred marine ciliate Pleuronema coronatum (Ciliophora, Scuticociliatida) were measured. Linear regression analysis of the results highlighted the close relationships between doses of the medicines and mortalities of the organisms, thus providing a capability to predict toxicity effects from the dose. Toxic effects of the medicines on the ciliates were described in the present paper, and the median lethal concentrations (LC₅₀ values) were given. Results of measurements indicated that 2 h-LC₅₀ and 12 h-LC₅₀ values of formalin on P. coronatum were 59.00×10⁻⁶ and 43.57×10⁻⁶, while those of Lugol’s solutions were 90.13 and 67.84×10⁻⁶ respectively. The tolerance of P. coronatum to formalin is apparently lower than that to Lugol’s iodine solution and potassium permanganate is a suitable medicine to kill ciliates in short time.