Number Of Rotifers Research Articles

Effect of the rotifer Lecane inermis, a potential sludge bulking control agent, on process parameters in a laboratory-scale SBR system

The influence of a high density of rotifers, which is known to be able to control filamentous bacteria, on the parameters of an activated sludge process was examined in four professional laboratory batch reactors. These reactors allow the imitation of the work of a wastewater treatment plant with enhanced nutrient removal. The parameters, including oxygen concentration, pH and temperature, were constantly controlled. The experiment showed that Lecane rotifers are able to proliferate in cyclically anaerobic/anoxic and aerobic conditions and at dissolved oxygen concentrations as low as 1 mg/L. In 1 week, rotifer density increased fivefold, exceeding the value of 2,200 ind./mL. The grazing activity led to an improvement in settling properties. Extremely high numbers of rotifers did not affect the main parameters, chemical oxygen demand (COD), N-NH(4), N-NO(3), P-PO(4) and pH, during sewage treatment. Therefore, the use of rotifers as a tool to limit the growth of filamentous bacteria appears to be safe for the entire wastewater treatment process.

베타(Betta splendens)의 부화 후 로티퍼(Brachionus calyciflor)와 물벼룩(Moina macrocopa)의 섭취, 소화속도 및 성장

The purpose of this study was to determine how an ornamental fish, such as the fighting fish, Betta splendens would respond to the use of freshwater live-prey, such as rotifers Brachionus calyciflorus and water fleas Moina macrocopa. Ingested quantity, digestive velocity and somatic growth were compared between larvae fed a freshwater rotifer and those fed boiled yolk. Food efficiency and somatic growth were compared between larvae that were fed freshwater water fleas and those fed a micro-diet developed for flounder (, I-hwa Ltd.). The number of rotifers ingested by larvae reached a maximum of 191 per day. However, based on the number ingested per hour and the digestive velocity of consumed rotifers, the maximum ingestible and digestible number of rotifers was calculated to be 272 per day. A maximum of 67 individuals (mean, 49.8 individuals) could be completely digested within the 1-h period from 90 to 180 min after feeding. Somatic growth was enhanced in larvae that were fed rotifers compared to those fed boiled yolk. Larvae exhibited greater growth at rotifer densities of 30 and 40 per mL than at lower densities. Among the water-flea (M. macrocopa and Bosmina sp.) and micro-particle diets, feeding with M. macrocopa resulted in the greatest somatic growth of larvae during the water-flea feeding stage.

Sub-lethal exposure to ultraviolet radiation reduces prey consumption by Atlantic cod larvae (Gadus morhua)

Levels of ultraviolet-B radiation (UV-B: 280–315 nm) reaching the earth’s surface have increased over the past few decades due to ozone depletion. It is well documented that exposure to UV-B radiation increases mortality in marine fish larvae. However, few studies have examined sub-lethal effects of UV-B radiation such as, for example, the possibility that it affects prey consumption by fish larvae. Atlantic cod larvae were exposed to a sub-lethal level of ultraviolet-B radiation (UV-B: 280–315 nm) for 15 h. After the exposure, rotifers (4/mL) were fed to cod larvae at three different post-exposure intervals (20 min, 3 and 6 h). Trials were replicated three times for each post-exposure interval. The number of rotifers in the gut and the percent of empty guts (number of fish with empty gut/number of fish examined × 100) were analyzed. Results were compared to those of unexposed fish (the control treatment). UV-B exposed cod larvae had consumed significantly fewer rotifers than control fish at all post-exposure intervals. There was no significant difference in the frequency of empty guts between fish in the UV-B treatment versus fish in the control treatment at any of the post-exposure time points (although the difference at 20 min post-exposure was borderline significant). These observations suggest that cod larvae exposed to sub-lethal levels of UV-B have lower net energy gain which may lead to reduced growth rate and possibly poorer survival.

Zooplankton of the Argazi reservoir (Southern Urals, Russia) and its long-term changes

(up to 11 g/m 3 ). Rotifers are the leading group in the plankton of the reservoir. Compared to the early 1960s, the abundance and biomass of zooplankton has increased by 5–10 times. The disappearance of some plank� ton forms and the emergence of new ones, as well as an increased number of rotifers and some crustaceans by

Physicochemical and biological dynamics in a coastal Antarctic lake as it transitions from frozen to open water

AbstractPony Lake, at Cape Royds, Antarctica, is a shallow, eutrophic, coastal lake that freezes solid in the winter. Changes in Pony Lake's physicochemical parameters and microbial community were studied during the transition from ice to open water. Due to rising water temperatures, the progressive melt of the ice column and the gradual mixing of basal brines into the remaining water column, Pony Lake evolved physically and chemically over the course of the summer, thereby affecting the microbial community composition. Temperature, pH, conductivity, nutrients and major ion concentrations reached their maximum in January. Pony Lake was colonized by bacteria, viruses, phytoflagellates, ciliates, and a small number of rotifers. Primary and bacterial production were highest in mid-December (2.66 mg C l-1d-1and 30.5 μg C l-1d-1, respectively). A 16S rRNA gene analysis of the bacterioplankton revealed 34 unique sequences dominated by members of theβ- andγ-proteobacterialineages. Cluster analyses on denaturing gradient gel electrophoresis (DGGE) banding patterns and community structure indicated a shift in the dominant members of the microbial community during the transition from winter ice, to early, and late summer lakewater. Our data demonstrate that temporal changes in physicochemical parameters during the summer months determine community dynamics and mediate changes in microbial species composition.

Suppression of Meloidogyne incognita in different agricultural soils and possible contribution of soil fauna

A total of 12 soils collected from different agricultural fields, having different backgrounds of organic input, were evaluated for their suppressive potential against Meloidogyne incognita. Second-stage juveniles (J2) of M. incognita were inoculated into the soils and their survival was evaluated. The number of M. incognita J2 5 days after inoculation differed depending on soil and was significantly lower in two soils, suggesting higher suppressiveness against M. incognita in these soils. This was confirmed by an experiment using tomato as a test plant, in which the gall formation was significantly lower in the two soils than in other soils. To estimate the contribution of below-ground biota to the suppressiveness, numbers of nematodes (predator, omnivore, bacterivore and fungivore) and other soil fauna such as tardigrades and rotifers, were counted. Some soil chemical and biological properties were also measured. Results from multiple linear regression analysis suggested that the number of rotifers, microbial activity, soil pH and total C may be involved in the suppression. The relationship between the suppressiveness and soil chemical and biological parameters is discussed.

Food consumption and selectivity by larval yellowtail kingfishSeriola lalandicultured at different live feed densities

Live food supply is a key factor contributing to the success of larval fish rearing. However, live food densities vary greatly between fish species and management protocols across fish hatcheries. The growth, survival, food selection and consumption of yellowtail kingfish larvae were examined at different regimes of live food supply in an attempt to identify a suitable live food feeding protocol for larval rearing in marine fish. This study was divided into two feeding phases: rotifer phase from 3 to 14 DPH (phase I) and Artemia nauplii phase from 15 to 22 DPH (phase II). In phase I, four rotifer densities (1, 10, 20 and 40 mL−1) were used. In phase II, Artemia started at 0.8 nauplii mL−1 on 15 DPH, and then the density of Artemia was daily incremented by 50%, 70%, 90% and 110%, respectively, in four treatments from 15 to 22 DPH. In phase I, rotifer density significantly affected larval growth, but not survival. By 7 DPH, the number of rotifers consumed by fish larvae reached 170–260 individuals, but did not significantly differ between rotifer densities. During cofeeding, fish larvae selected against Artemia nauplii by 10 DPH, but by 14 DPH Artemia nauplii became the preferred prey item by fish larvae exposed to the 10, 20 and 40 rotifers mL−1. In phase II, both fish growth and survival were affected by Artemia densities. Fish daily consumption on Artemia by 20 DPH reached 500–600 individuals but did not significantly differ between prey densities. The result suggests that rotifer densities be offered at 20–40 mL−1 before 6 DPH and 10–20 mL−1 afterwards to support larval fish growth and survival. Likewise, Artemia is recommended at a daily increment of 90–110% of 0.8 mL−1 from 15 to 22 DPH. This study proposes a management protocol to use appropriate type and quantity of live food to feed yellowtail kingfish larvae, which could be applicable to larval culture of other similar marine fish species.

The Influence of Temperature on the Effectiveness of Filamentous Bacteria Removal from Activated Sludge by Rotifers

We investigated the feeding of the rotifer Lecane inermis on filamentous bacteria to determine if the ability of rotifers to remove filaments depends on temperature. The bacteria originated from two treatment plants, one of which was dominated by Microthrix parvicella and the other by Nostocoida limicola-like organisms. The experiments showed that the number of rotifers increased with temperature, and thus the ability of rotifers to reduce the number of filaments also increased with temperature. At 8 degrees C, their removal effectiveness was low, but the rotifers were able to survive at this temperature. When presented with sludge containing N. limicola-like microorganisms at 20 degrees C, the rotifers reduced the number of bacteria by 95%. In the case of M. parvicella, the reduction reached 50%. The results confirmed that Lecane are capable of controlling the growth of bacteria responsible for sludge bulking. This is the first report indicating that the seasonality of bulking may be the result of the activity of filamentous bacteria grazers, which is temperature dependent.

Spatial distribution of rotifers (Rotifera) in monospecies beds of invasive Vallisneria spiralis L. in heated lakes

Abstract Species abundance and richness of rotifer communities occupying monospecies beds of Vallisneria was studied in Lake Licheńskie included in the open cooling system of heat and power stations. Differences were found in rotifer numbers, species composition and diversity between sampling points within the same location and between the locations. Factors that seem to be responsible for the high diversity of rotifer communities inhabiting Vallisneria beds are: large-scale horizontal diversity (between macrophyte patches), small-scale horizontal diversity (within patches) and the high vulnerability of Vallisneria epiphyton to disturbances caused by wave action.

Bacillus cereus and Bacillus subtilis used as probiotics in rotifer (Brachionus plicatilis) cultures

Since live food is a key factor in fish and invertebrate larvae rearing, the objective of this study was to evaluate the probiotic potential of two Gram positive Bacillus species: Bacillus cereus (CCBM-2) and Bacillus subtilis (CCBM- 64), originally isolated from marine sediments in the Colombian Caribbean, in rotifer Brachionus plicatilis cultures. The enzymatic activity and antibacterial activity against pathogens of B. cereus and B. subtilis were measured in vitro. Direct supplementation of the rotifer culture water with both bacteria was also carried out and the effect was measured in vivo by estimating the density of rotifers and bacterial counts in the culture. The results indicated that extracellular products of both bacteria strongly inhibited the growth of AeromonA. hydrophila and Vibrio alginolyticus isolated from diseased fish. Enzyme API ZYM assays showed that both bacteria have esterase lipase, leucine arylamidase, acid phosphatase, lipase, and Naphthol-AS-BI- phosphohydrolase activities. Furthermore, it was observed that the addition of B. subtilis to the rotifer culture water resulted in a significant increase in rotifer numbers and a reduction of Vibrio levels. B. subtilis appears to be a promising probiotic for rotifer cultures, but further research is required to determine the capacity in controlling A. hydrophila and V. alginolyticus when administered via rotifers to fish larvae.

Daphnia–rotifer interactions in Patagonian communities

In fishless ponds of extra-Andean Patagonia, large Daphnia often may severely limit the abundance of small rotifers by mechanical interference (ingestion and damage after rejection). In ten laboratory experiments, 15–20 rotifers were exposed to one large daphniid for 1 day in 80 ml water with Cryptomonas erosa (5 × 103 cells ml−1). Both D. cf. pulex (3.6 mm) and D. cf. obtusa (3.4 mm) imposed significant mortality on Keratella tropica and newborn Brachionus angularis and Brachionus calyciflorus, but not on the larger neonates of Brachionus rubens or adults of B. angularis and B. calyciflorus. B. rubens neonates avoided the possibility of interference by rapidly attaching to Daphnia. The number of susceptible rotifers killed per Daphnia day−1 was 2–8 for D. cf. obtusa and 8–15 for D. cf. pulex; rotifer-based clearance rates per Daphnia day−1 were 10–35 and 35–65 ml, respectively. When large daphniids occurred in Laguna Los Juncos in late September and October 1997, the only common plankton rotifer was the large and probably well-protected Keratella morenoi (total length = 210 μm). Still, microscopic examination of gut contents revealed three K. morenoi in a 3-mm D. cf. obtusa and one in a 3.5-mm D. dadayana.

Optimization of Indoor Production of Fresh Water Rotifer, Brachionus calyciflorus, b: Feeding Studies

Brachionus calyciflorus is commonly found in fresh water ponds. Its production depends on unrelenting supply of Chlorella in sufficient quantity. In the current studies a water sample was collected from fish culture ponds by Wisconsin plankton net (64 µm mesh). The freshly collected stock was concentrated and fractionated by passing through 600, 200, 125, 75 and 38 µm sieves arranged vertically with gradual decrease in pore size. The pure Brachionus calyciflorus were fed on Chlorella available in the laboratory. Algae was gradually replaced by yeast to reduce dependency on labour intensive live food. Maximum number of rotifers 413 ml , was observed when they were fed on 160:32 yeast:algae ratio by weight combination. -1 Ciliates and cyclops posed a major threat during culture and frequent crashes were observed due to this menace. Cyclops were selectively eradicated from the rotifer culture at 0.09 DDVP after 20 h of exposure but not ciliates. There was no selective mortality in ciliates at any stage. Nevertheless both ciliates and rotifers were dead at 0.2 ppm. Simple method of cyst preservation is mentioned.

Freshwater rotifers from Hordaland, western Norway, with a survey of freshwater rotifers previously found in Norway

Bjørklund BG. 2009. Freshwater rotifers from Hordaland western Norway with a u survey of freshwater rotifers previously found in Norway. Fauna Norvegica29: 11-54. A total of 156 species (or subspecies) o rotifers, mostly non-planktonic, have been identified from freshwater or slightly brackish-water localities in the county of Hordaland; 83 are new to Norway and 24 others are new to the county. One hundred of the species were collected from the two valleys of Eksingedalen and Teigdalen in spring and summer 1967. Samples were taken on the shallow shores of lake-like parts of the rivers, and in pools, tarns and small lakes. Forty more or less euryhaline fresh­water rotifers were also collected during studies of slightly brackish-water localities around Bergen in 1963-1969. A number of freshwater rotifers were collected at several localities in and around Bergen in 1968-1970, and on the western part of Hardangervidda. Of those so far identified ,23 are new to Norway and 8 more are new to the county. They are therefore included in the species list. A few additional ones are referred to in the taxonomical notes. All the species are listed with localities and habitat categories, or, in the case of the last-mentioned ones, just the district where they were collected. The paper includes notes, measurements and ,in most cases, figures regarding 44 little known, variable or taxonomically problematical species, especially in the genera Cephalodella and Trichocerca. Comments are given on the distribution , abundance and diversity of the species. The paper presents asurvey of previous investigations on rotifers in Norway, listing 200 previously recorded freshwater (a few euryhaline) rotifers, giving other names, the authors who recorded the finds and, in most cases, the counties where the species were collected.

A method for efficient extraction of rotifers (Rotifera) from soils

Abstract Rotifers are a group of soil animals which are not commonly quantified. The most recent data originated from soil studies focussed on nematodes and various modifications of the Baermann funnel, which is not suitable for rotifers. The present study developed a method for quantitative extraction of rotifers, which gives representative results describing rotifer populations and facilitates subsequent identification to the species level. The LC extractor recovered rotifer numbers that were two orders of magnitude higher than what was extracted from the Baermann funnel. The method involves spreading a soil sample on a plastic sieve and uses a very thin layer of cellulose submerged in distilled water in a Petri dish. The Petri dish is situated on a cooled panel and light from the top by fluorescent lamps. The temperature of the base panel which gave the best extraction results was determined experimentally to be 5 °C. Rotifers were not able to withstand any heating from the top, which drastically reduced extraction results.

Production and Collection of Copepod Nauplii from Brackish Water Ponds

Copepod nauplii are a nutritious food item for first-feeding marine fish larvae. Unfortunately, mass culture techniques for producing copepod nauplii are not well established. Copepod nauplii can be collected from wild zooplankton populations or specially prepared ponds and transferred to larval fish tanks for feeding. This study evaluated the use of two trapping methods for harvesting zooplankton, particularly copepod nauplii, from fertilized ponds and the impact on the zooplankton population. Nine, 0.11 ha brackish-water (∼2-7 ppt salinity) ponds were filled and fertilized with organic and inorganic fertilizers. The change in zooplankton abundance, mainly rotifers, nauplii and adult copepods, was monitored in the ponds for 22 d following initial pond filling. Beginning on day 8, three ponds were trapped with a large plankton net (Trap I), three with a pump and bag trap method (Trap II), and three ponds were not trapped. The ponds were trapped with the corresponding method for 1 h per day, for 15 d. The two trapping methods were similar in their efficiency to harvest nauplii, averaging 8,383,400 ± 2,508,378/h and 6,695,822 ± 433,533/h for Traps I and II, respectively. The zooplankton harvested by Trap I was not correlated to the densities in the ponds. However, the number of rotifers and nauplii harvested by Trap II was correlated to the rotifer and nauplii densities in the ponds. Both trapping methods were similar in terms of labor requirements and ease of use. Both methods were effective in collecting zooplankton without negatively impacting pond abundance.

Assessing rotifer diapausing egg bank diversity and abundance in brackish temporary environments: an ex situ sediment incubation approach

The hatching of diapausing eggs from sediment samples of ponds and lakes is a fast, easy, and economical technique proven useful for the assessment of diversity and abundance of zooplankton in permanent habitats. Here, we extend and optimize this approach for temporary brackish ponds which may experience great within-year variation in salinity conditions. We studied the species and numbers of rotifers emerging from the sediments of several brackish ponds and saline lakes from Eastern Spain incubated at the full range of salinity conditions observed at the study sites. On average, 82 % of the total observed species in weekly sampling for one year were detected in a single sample of both the sediments and water column. No statistical difference was found between both methods. However, some rotifer species were only observed in the water column samples, but not in sediment hatchlings, and vice versa. We concluded that both methods are not exhaustive by themselves but are complementary. Salinity affected the estimation of both rotifer richness and the density of individuals of each rotifer species that emerged from the incubated sediments. Differences in the density of emerging animals were also found among sites and among combinations of sites and salinities. The latter result indicates that in order to obtain an estimate of the emergence rate for each rotifer species present at a site, it is necessary to incubate sediments at salinity conditions close to their local values.

Influence of light intensity on feeding, growth, and early survival of leopard coral grouper ( Plectropomus leopardus) larvae under mass-scale rearing conditions

This study investigated the effect of different light intensities on feeding, growth and survival of early stage leopard coral grouper Plectropomus leopardus larvae. Four different light intensities (0, 500, 1000 and 3000 lx) were used and larvae were kept under constant light conditions from 0 day after hatching (DAH) to 5 DAH. The larvae were fed a small S-type of Thai strain rotifers at a density of 20 individuals/mL from 2 DAH. The number of rotifers in larval digestive organ and total length of larvae were examined at 3 h intervals between 04:00 and 22:00 h on 3 DAH, and thereafter at 6 h intervals until the end of the experiment (5 DAH). Four experimental trials of the larval rearing were repeated using by 60 kL mass-scale rearing tanks. The results indicate that coral grouper larvae are visual feeders and their food intake increases with increasing light intensity. Food intake of larvae reared at 3000 lx was significantly higher than those reared at 0–1000 lx on 3 DAH despite being the first-feeding day ( P < 0.01). On 4 DAH, total length of larvae reared at 3000 lx was significantly larger than those reared at the lower light intensities (0, 500 and 1000 lx), and thereafter light intensity significantly influenced larval feeding and growth until the end of the experiment. Survival on 5 DAH did not show a significant difference between light intensities, but survival rate at 3000 lx and 1000 lx had a tendency to be higher than those reared at the lower light intensities (0 and 500 lx). In contrast, larvae reared at 0 lx exhibited stagnant and/or negative growth. These results indicate that light intensity is significantly the factor affecting larval feeding, growth, and survival in coral grouper larvae under the rearing conditions.

Note on a Highly Diverse Rotifer Assemblage (Rotifera: Monogononta) in a Laotian Rice Paddy and Adjacent Pond

AbstractDuring August 1999, the authors conducted a sampling campaign in the PDR Laos, in order to contribute to the chorology of rotifers in the region. Two samples, collected from a rice paddy and an adjacent pond near Vientiane, Laos, contained a total of 135 rotifer species including several that appear new to science or that warrant taxonomical or biogeographical comments. No new species can be named, but Cephalodella boettgeri Koste and Floscularia armata Segers are recorded for the second time ever after their description from South America, and Parencentrum lutetiae (Harring and Myers) and Polyarthra luminosa Kutikova are new to Southeast Asia. This raises the number of rotifers recorded from Laos from 9 to 130. The diversity recorded is remarkable, especially when compared with that of similar habitats in the Thai part of the floodplain of River Mekong and its tributaries. Different agricultural practices may account for the difference in species richness. Similar highly diverse rotifer faunas are known to occur in natural, tropical and subtropical floodplain systems only. This accords with the view that rice paddies can be regarded as artificial wetlands or floodplain systems, which, if managed taking biodiversity concerns into account, may have a potential for the conservation of freshwater biodiversity. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

An individual-based population model for the prediction of rotifer population dynamics and resting egg production

Most species of rotifers have a combination of sexual and asexual reproduction, with sexual reproduction resulting in resting eggs, which can lay dormant for long periods. The occurrence of sexual reproduction affects population dynamics through the temporary presence of male rotifers, and a reduction in the growth of the number of female rotifers. A previously published, individual-based model used dynamic energy budget theory to describe rotifer food intake, growth, egg production, and mortality, but assumed asexual reproduction only. In the current study, we have expanded the model to describe the entire reproductive cycle of the rotifers, making it usable for investigating relationships, such as those between the signal triggering mictic egg production, and the timing and number of resting eggs produced. The model is intended for use in predicting the specific future development of cultures, for instance, as a process model in rotifer or resting egg production for aquaculture.

Mass Production of Freshwater Rotifer, Brachionus calyciflorus, Under Different Diets and Regimes

ABSTRACT The production ability of freshwater rotifer, Brachionus calyciflorus, cultured with two algal species, Chlorella vulgaris, and Spirulina platensis, and a baker's yeast, Saccharomyces cerevisiae, were studied using semicontinuous culture method. B. calyciflorus was fed with the above three types of food at five different concentrations (125, 250, 500,750, and 1,000 μg/mL). Among the three different types of diet, maximum production of B. calyciflorus (489.20 ±10.91 individuals/mL; P < 0.05) was obtained with C. vulgaris, followed by S. cerevisiae, and S. platensis. Moreover, in each of the three diets, the maximum rotifer production was obtained at a particular concentration (C. vulgaris, 750 μg/mL; S. cerevisiae, 750 μg/mL; and S. platensis, 500 μg/mL) beyond which the rotifer production decreased. The peak production due to C. vulgaris (489 individuals/mL) was better than S. cerevisiae (321 individuals/mL) when the number of rotifers was considered. The present study indicates that the quantity and quality of food have a significant role on the rotifer production and that C. vulgaris at 750 μg/mL appears suitable to feed to rotifers for maximal production.