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PubMed2000

[Effect of initial population density on resting egg formation of rotifer Brachionus calyciflorus].

With the method of population accumulative culture, the effect of initial population density on the formation of resting eggs of freshwater rotifer(Brachionus calyciflorus), and on the rates of mictic female and fertilization was studied. During 11 days culture, the productivity and the formation efficiency of resting eggs, and the mean rate of mictic female were the biggest when the initial population density was 1.0-10.0 ind.ml-1, second by the density of 20.0 ind.ml-1, and the lowest by the density of 50.0 ind.ml-1. There was no significant effect of initial population density on the fertilization rate. Statistical analysis on maximum formation efficiency of resting eggs, their emergence and productivity showed that when the production of resting eggs was large-scaled proceeded, the feasible initial population density should be 10.0 ind.ml-1, and the corresponding time should be 6 days to obtain a higher yield of resting eggs and a higher formation efficiency.

Animals↗
PubMed2001

Sludge reduction potential of metazoa in membrane bioreactors.

In order to check the sludge reduction capacity of metazoa in a membrane bioreactor (MBR), pilot-scale studies were conducted. Three MBRs had been set in a wastewater treatment plant at Tokyo, Japan and they were receiving real wastewater. Initially pH inside the three MBRs was controlled as pH 7, 6 and 5 respectively. Then metazoa population was monitored along with MLSS change. It was found that the presence or absence of the metazoa population did not have any significant effect on the increasing pattern of MLSS. In the MBR with pH 6 highest accumulation of sludge was observed though a high and steady level of metazoa (1,000-2,000 per ml) was present there. But in this MBR a lot of metazoa attached in the membrane was also observed and here the increase in transmembrane pressure was less than in the other two. So, metazoa population especially the attached one in the membrane plays an effective role in fouling control of the membrane. Presence of attached media may provide a suitable niche for metazoa in the process. So, attached media known as DB lace was also inserted in MBRs for testing its capacity along with inoculum of oligochaete worms. Accumulation of sludge was not satisfactory in the attached string and it seems that inoculated worm could not adjust to the environment as they were not sludge originated. So, in the next experimental stage, attached media was inserted in the form of a bundle and this time no inoculation of worm was used. A steady metazoa population was observed in the system but the accumulation of sludge in the attached media was the same as before.

Animals↗
PubMed2001

Biota participating in wastewater treatment in a horizontal flow constructed wetland.

During the period 1996-1997, three constructed wetlands with sub-surface horizontal flow were investigated. All systems are designed to treat municipal sewage from small villages (150, 200 and 300 PE). The survey included microscopical identification of organisms in both wastewater and filtration substrate. The organisms were used as an indication of oxygen conditions (aerobic, anoxic and anaerobic) in the particular microenvironment. Saprobiological terms characterizing different levels of saprobity were employed to characterize inflowing wastewater, filtration bed and outflowing water. The occurrence of organisms was correlated with BOD5 values in particular profiles. It has been found that the biocenosis in the inflowing wastewater differs from those found in the filtration bed and water outflowing from the vegetated beds. The organisms were grouped into those living under anaerobic and anoxic conditions and those living under aerobic conditions. More than 70 species of bacteria, amoebae, ciliates, rotifers, colorless flagellates, cyanobacteria and algae were found and the most important 45 species were figured in a plate together with saprobiological information for each species. Biota of the inflowing water is usually restricted to bacteria, ciliata and colorless flagellata while the organisms found in outflowing water as well as in periphyton growing on outflow structures indicate 2-3 levels better quality.

Animals↗
PubMed2002

[Effects of cumulative parthenogenetic generation and age of amictic female on the reproduction of rotifer Brachionus calyciflorus].

Effects of cumulative parthenogenetic generation and age of amictic female on mictic female production and fecundity of the rotifer Brachionus calyciflorus were studied by means of individual culture. The results showed that percentage of total mictic females produced by the parental females in each of four generations increased with the increasing generations. More mictic females were produced from younger maternal amictic females. Amictic offspring from older mothers produced more mictic daughters. There was no significant effect of the cumulative parthenogenetic generation on the mean number of eggs produced by amictic females per life cycle, and no significant effect of the age of amictic female on the mean number of eggs produced by the offspring of amictic female.

Aging↗
PubMed2002

[Effect of suspended silt from dredging at Yangtze estuary on Brachionus plicatilis].

The effect of suspended silt from dredging at Yangtze estuary on Brachionus plicatilis was investigated by clonal culture (to construct life table) and population accumulative culture. The intrinsic increasing rate of the rotifer population was greatly reduced under different concentrations (1, 3, 5, 7 and 9 mg.ml-1) of silt, from 29.6% to 64.1%, and to a maximum of 130.0%. The suspended silt affected population survival rate, rather than its reproduction rate. In accumulative culture, the densities of female, males, parthenogenetic eggs, and resting eggs in the population were not affected by silt. It was concluded that the presence of suspended silt should have a certain negative influence on the rotifer population in dredging Yangtze estuary.

Animals↗
PubMed2002

[Effects of food concentration on population growth, body size, and egg size of the freshwater rotifer Brachionus angularis].

With the food Chlorella pyrenoidosa and the method of population accumulative culture, the effects of food concentration on the population growth, body size, and egg size of the freshwater rotifer Brachionus angularis were studied. The results showed that there were very significant effects of food concentrations on the population growth rate, body size and egg size. The relationship between the population growth rate and the food concentration was curvilinear correlation. When the food concentration was 8.2453 x 10(6) cells.ml-1, the population growth rate reached it's maximum, 0.6085 d-1. Body size tended to enlarge with increasing food concentration. At the intermediate range of food levels between 6.0 x 10(6) cells.ml-1 and 9.0 x 10(6) cells.ml-1, the egg volume was larger than those at the other food concentrations.

Animals↗
PubMed2003

Identification of phototransformation products of prednisone by sunlight: toxicity of the drug and its derivatives on aquatic organisms.

Solar simulator irradiation of an aqueous suspension of prednisone, a widely prescribed drug, produces seven photochemical derivatives. The compounds have been identified on the basis of their physical features. All the chemicals have been tested to evaluate their toxic effects on freshwater organisms from different trophic levels. The rotifer Brachionus calyciflorus and two crustaceans, the cladoceran Daphnia magna and the anostracan Thamnocephalus platyurus, were used to perform acute toxicity tests. Chronic toxicity tests have been performed on the alga Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum) and the crustacean Ceriodaphnia dubia. The results showed low acute and chronic toxicity of prednisone. Some of the photoproducts had high toxic effects on C. dubia.

Animals↗
PubMed2003

Predation of Cryptosporidium oocysts by protozoa and rotifers: implications for water quality and public health.

Predation by free-living protozoa and rotifers was investigated as a possible mechanism for the removal of Cryptosporidium parvum oocysts in aquatic ecosystems including wastewater treatment plants. Free-living ciliated protozoa (Stylonychia mytilus, Paramecium caudatum and an unidentified wastewater wetland ciliate), an amoeba (Acanthamoeba culbertsoni) and rotifers, all commonly found in aquatic ecosystems, were exposed to varying doses of C. parvum oocysts. All organisms investigated ingested oocysts. Predation activity and rates of ingestion varied with predator species and prey density. Ciliated protozoa demonstrated greater predation activity than A. culbertsoni or rotifers when exposed to 2 x 10(5) oocyst/mL for up to 3 h. Greatest predation after 1 h exposure was observed in P. caudatum, the largest ciliate, with on average 1.9 oocysts/cell (range 0-9 oocysts/cell). Stylonychia mytilus and the wetland ciliate had a similar mean ingestion of around 0.3 oocysts/cell, with numbers internalised ranging from 0-3 oocysts/cell. Rotifers ingested on average 1.6 oocysts/individual (range 0-7 oocysts/individual) whilst amoebae ingested on average 1.8 oocysts/cell after 2 h exposure (up to 3 oocysts/cell). Grazing activity by P. caudatum was demonstrated at a variety of prey levels ranging from 9 to 9,000 oocysts. Numbers of oocysts internalised by Paramecium frequently exceeded the reported human infective dose of 30 oocysts. In general, numbers of internalised oocysts increased with incubation time of up to 20-30 min although the rate of accumulation was slower at lower dose levels. The significance of predation on the fate of Cryptosporidium oocysts in the environment is discussed.

Animals↗
PubMed2002

[Relationship between sexual reproduction, population growth and resting egg production of freshwater rotifer Brachionus calyciflorus].

Using exponential and logistic growth models, the effects of sexual reproduction frequency and the proportion of a female's daughters reproducing sexually on population growth rate and resting egg production of freshwater rotifer Brachionus calyciflorus were examined by computer simulation. Within the parameters of the simulation, the percentage of micitc females in the offspring required for maximum resting egg production increased from 9% to 69%, when the frequency of sexual reproduction decreased from 100% to 20%. The increase of density-dependent limitation (the value of K decreased from 1000 to 100) made this percentage increase from 18% to 69%, and resting egg production decrease from 1072.10 to 133.67. The relationship between the population growth rate (r) and the optimum percentage of mictic females in the offspring required for maximum resting egg production was best described by curvilinear regression. When sexual reproduction became more frequent and density-dependent decreased, The population with the percentage of mictic females in the offspring in 10-30% had a bigger resting egg production.

Animals↗
PubMed2003

[Comparative studies on individual growth and development of three Brachionus angularis strains].

The embryonic developmental period (De), pre-reproductive period (Dp), the least generation time (Tg), body size of juveniles and adults, egg volume and relative egg volume of three strain Brachionus angularis from Qingdao, Guangzhou and Wuhu were studied with Scenedesmus obliquus at 2.4 x 10(6) cells.ml-1 as the rotifers' food at 25 degrees C. We found that there were significantly different in De, Dp and Tg of three strains. De of WH strain was the top, and subsequently was GZ strain and QD strain. QD strain had the longest Dp, but GZ strain had the shortest. Tg in GZ strain was the shortest, and QD strain, and WH strain were longer, respectively, but no significantly difference existed in the later two. De tended to decrease as the relative egg volume increased in the three strains. Body size at the same stage in pre-reproductive period of three strains was significantly different. WH strain had the largest body size during all of the stages. The relationships between body size and the age of the juvenile of QD, GZ and WH strain were all curvilinear. The variance of the neonates and the adults was 244.24% in WH strain, and 182.89%, 156.28% in QD and GZ strain, respectively. The adults' body size, egg size, and relative egg size was significantly different in three strains.

Animals↗
PubMed2003

[Effects of food component and concentration on population growth, body size, and egg size of freshwater rotifer Brachionus rubens].

The effects of food component and concentration on the population growth, body size, and egg size of freshwater rotifer Brachionus rubens were studied using population accumulative culture method. The results showed that there were very significant effects of food component and concentration on the population growth rate, body volume and egg volume. Among three types of algal food, the population growth rate of rotifers fed with Chlorella pyrenoidosa was lowest, and that fed with Scenedesmus obliquus was the highest. Rotifers fed with C. pyrenoidosa had the smallest body volume, but there were no significant difference between the two others. The relationship between population growth rate and food concentrations was curvilinear, and it could be described as Y = -0.0040X2 + 0.0409X + 0.4471. The body and egg volumes tended to be smaller, when the food concentrations were higher than 6.0 x 10(6) cells.ml-1 and or lower than 3.0 x 10(6) cells.ml-1.

Animals↗
PubMed1992

Cyst-based toxicity tests. VI: Toxkits and Fluotox tests as cost-effective tools for routine toxicity screening.

During the last two decades microbiotests have been developed which are independent of recruitment, maintenance and/or culturing of live stocks of test organisms. "Culture and maintenance free" microbiotests have been worked out in the Laboratory for Biological Research in Aquatic Pollution at the University of Ghent, with selected aquatic invertebrates. The new approach is based on the use of "resting stages" (cysts) as inert biological material from which live test organisms can be hatched "on demand". The "cyst-based" bioassays have recently been miniaturized in Toxkits. Four cyst-based screening tests have reached the stage of commercialization: two freshwater 24h-LC50 tests (Rotoxkit F and Streptoxkit F) and two estuarine/marine 24h-LC50 bioassays (Rotoxkit M and Artoxkit M), based on cysts of rotifer and crustacean species, respectively. Recently, the same laboratory has also been focusing on the development of a "rapid" (one hour) sublethal bioassays with aquatic invertebrates. The so called "Fluotox" screening test is based on the visual observation of in vivo inhibition of an enzymatic process, using a fluorescent substrate. Besides the advantages of rapidity and cost-effectiveness, the Fluotox assay also appears to have a remarkable predictive potential for mortality, as displayed by the remarkable correlation between the Fluotox 1h-EC50's and conventional 24h-LC50's with the same species.

Animals↗
PubMed2003

[Effects of Alexandrium tamarense and Prorocentrum donghaiense on rotifer Brachionus plicatilis population].

The effects of Prorocentrum donghaiense and Alexandrium sp., causative species of harmful algal bloom of East China Sea in May 2002, on rotifer Brachionus plicatilis population were studied in the laboratory. The results showed that Alexandrium tamarense (ATHK) had a lethal effect on B. plicatilis and the 48hLC50 was about 1300 cell.ml-1. The toxin comparison of different fractions showed that the algal culture and re-suspended algal cells had the adverse effects, and the alga at earlier growth phases showed a stronger impact, indicating that the inhibitory effect was related with the activity of the living algal cells. P. donghaiense at high densities (4 x 10(4), 5 x 10(4) and 10 x 10(4) cell.ml-1) had an adverse effect on B. plicatilis population, while at low densities (1 x 10(4), 2 x 10(4) and 3 x 10(4) cell.ml-1), the alga could be used as food for rotifer population. When the two algae were mixed, the lethal effect of A. tamarense could be decreased by P. donghaiense. The results indicated that the above HAB event could affect the micro-zooplankton population in the occurrence area of East China Sea.

Animals↗
PubMed2004

[Suspending particulates in rotifer-culturing pond ecosystem].

A comparative study on the structure and dynamics of suspending particulates in static and current water rotifer-culturing ponds showed that the total content of suspending particulates varied from 6.76 to 65.39 mg.L-1, with an average of 11.50 mg.L-1 in static water ponds, among which, organic pariculates accounted for 66.8%, while inorganic particulartes occupied 33.2%. In the organic particulates, both particulate detritus and bacteria accounted for 31%, while phytoplankton and zooplankton occupied 30.5% and 5.3%, respectively. The amount of suspending particulates in current water ponds was 41.83 mg.L-1 in average, among which, organic pariculates accounted for 70.4%, while inorganic pariculates occupied 29.6%. In the organic pariculates, both particulate detritus and bacteria accounted for 39.2%, while phytoplankton and zooplankton occupied 30% and 1.2%, respectively. The content of suspending pariculates in static water ponds was less than those in current water ponds. Rotifer-culturing pond was a special type of ecosystem, where Brachionus plicatilis was the major consumer, its community structure was sample, and the abiotic factors were easy to be changed, which resulted in the dynamics of suspending pariculates content in ponds. The ratio of organic to total pariculates in rotifer-culturing ponds was higher, and the contents of both particulate detritus and bacteria were corresponding to that of plankton.

Animals↗