• Journal of Aquaculture
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• v.9 no.4
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• pp.453-459
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• 1996

Cellulase was purified from marine rotifer, Brachionus plicatilis, to homogeneity by using chromatographic methods. Purified enzyme is an endo-${\beta}$-1,4 glucanase and shows a strong hydrolytic activity against carboxymethyl (CM) -cellulose. The physicochemical parameters of enzyme activity were determined. The molecular weight of the purified protein was approximately 62 kDa as determined by SDS-polyacrylamide gel electrophoresis. The enzymatic capability to digest cellulose of Chlorella cell wall was compared with that of other well known cellulases from Thermomonospora fusca. Experiments involving Chlorella digestion indicated that CM-cellulase from marine rotifer, Brachionus plicatilis, could digest Chlorella very efficiently while cellulase purified from Thermomonospora fusca did not. From the result here, we propose that the cellulolytic system from marine rotifer is responsible for the hydrolysis of cellulosic wall of Chlorella, probing that rotifer digests Chlorella as a major live food.

• Journal of Aquaculture
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• v.9 no.4
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• pp.339-344
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• 1996

The effect of temperature ($24\~36^{\circ}C$ and salinities ($5\~30$ ppt) on hatching rate of the resting egg of the Korean rotifer, Brachionus plicatilis was investigated. The highest hatching rate of the resting egg was $85.7\%$ at $28^{\circ}C$ and 15 ppt. The hatching rates of the resting eggs with salinities were not significant at $326{\circ}C$ and $36^{\circ}C$. Hatching was faster at higher temperature. The resting eggs stored at $5^{\circ}C$ in dark hatched simultaneously within two days, however, those at $28^{\circ}C$ in dark hatched intermittently within 14 days. But, final hatching rate of the resting egg at $28^{\circ}C$ was higher at $28^{\circ}C$ than that at $5^{\circ}C$. With regard to drying temperature and time of resting egg, the resting egg dried at $30^{\circ}C$ for 1 hour showed the highest hatching rate ($46.4\%$).

• Proceedings of the Korean Aquaculture Society Conference
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• 2002.08a
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• pp.207-208
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• 2002

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.665-670
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• 2011

The rotifer Brachionus plicatilis is one of the most important food organisms in aquaculture. The resting eggs produced by mictic female rotifers are easily stored and hatched, making them useful as the starter for the mass culture of rotifers in marine larval culture. This study examined the optimum preservation method for resting eggs to ensure a high hatching rate. To produce resting eggs, the marine rotifer B. plicatilis was cultured with Nannochloris oculata (KMMCC 16). The resting eggs were harvested and cryopreserved using 5% and 10% methanol (MeOH), dimethylsulfoxide (DMSO), and glycerol as cryoprotectant agents (CPAs). The cryopreservation comprised slow or rapid freezing and the resting eggs were stored for one month in liquid nitrogen ($-196^{\circ}C$). The resting eggs were also dried at different temperatures (30, 40, and $50^{\circ}C$) and for different times (1, 2, and 3 h). In general, the hatching rates of the resting eggs preserved with CPA were higher than those without CPA and the slow freezing method was better than the rapid freezing method. However, the optimum CPA concentration for the hatching rate of the resting eggs varied with the freezing method and kind of CPA, and the CPA also affected the viability of the resting eggs. Dried resting eggs had a high, rapid hatching rate over 80%. The moisture content of the resting eggs cryopreserved in liquid nitrogen affected the hatching rate. Drying at $30^{\circ}C$ for 1 hour resulted in a high hatching rate of the resting eggs. In conclusion, drying at $30^{\circ}C$ for 1 hour and preservation in liquid nitrogen with the slow freezing method, without CPA, is recommended for a high hatching rate (ca. 95%) of rotifer resting eggs.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.658-664
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• 2011

Rotifers of the genus Brachionus are commonly used as a live food for larval fish, and rotifers of different sizes are preferred according the mouth size of the fish. Rotifer species vary in size, and individual size can depend on the temperature and salinity of the rearing environment. We investigated the effects of temperature and salinity for two species, B. plicatilis (250-300 ${\mu}m$) and B. rotundiformis (100-220 ${\mu}m$). Two strains of B. plicatilis (CCUMP 36 and 48) and two strains of B. rotundiformis (CCUMP 51 and 56) were received from the Culture Collection of Useful Marine Plankton (CCUMP) at Pukyong National University and cultured with the green alga, Nannochloris oculata (KMMCC 16) from the Korea Marine Microalgal Culture Center (KMMCC). The growth and size of rotifers were examined at three water temperatures ($16^{\circ}C$, $24^{\circ}C$, $32^{\circ}C$) and four salinities (20 psu, 25 psu, 30 psu, 35 psu) under continuous light (40 ${\mu}molm^{-2}s^{-1}$). The maximum density and growth rate of B. rotundiformis were greater than those of B. plicatilis. The lorica length of B. plicatilis ranged from 215.4 to 269.7 ${\mu}m$ and from 154.9 to 206.6 ${\mu}m$ for B. rotundiformis, depending on strain, temperature and salinity. Rotifers were smaller when cultured at high temperatures, regardless of salinity. B. rotundiformis preferred higher salinity than B. plicatilis. The results demonstrated that the size of rotifers could be controlled to some extent by temperature and salinity.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2002.05a
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• pp.334-335
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• 2002

• Korean Journal of Environmental Biology
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• v.34 no.3
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• pp.193-200
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• 2016

Toxicity assessment of heavy metals (As, Cr and Pb) has been investigated by using the rate of survival and population growth(r) of marine rotifer, Brachionus plicatilis. The survival rate was determined after 24 hours of exposure to As, Cr and Pb. As and Cr reduced survival rate in dose-dependent manner and a significant reduction were occurred at concentration of greater than 30 and $150mg\;L^{-1}$, but Pb had no effect on survival rate. The r was determined after 72 hours of exposure to As, Cr and Pb. As, Cr and Pb reduced r in dose-dependent manner and a significant reduction were occurred at concentration of greater than 5, 25 and $50mg\;L^{-1}$. The toxicity of heavy metals were ranked As>Cr>Pb, with $EC_{50}$ values of 12.98, 82.34 and $110.14mg\;L^{-1}$, respectively. The no-observed-effect-concentration (NOEC) of r in As, Cr and Pb exposure were 1, 12.5 and $50mg\;L^{-1}$, respectively. The lowest-observed-effect-concentration (LOEC) of r in As, Cr and Pb exposure were 5, 25, and $50mg\;L^{-1}$, respectively. From the results, the concentration of As, Cr and Pb (greater than 5, 25 and $50mg\;L^{-1}$, respectively) have toxic effect on the r of B. plicatilis in natural ecosystems. These results (including NOEC and $EC_{50}$) might be useful for the mixing toxicity assessment and toxic guide line of heavy metals in marine ecosystems.

• Korean Journal of Environmental Biology
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• v.35 no.4
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• pp.573-580
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• 2017

The oxicity assesment of Phenanthrene (PHE) has been investigated by using the rate (r) of survival and population growth in rotifer Brachionus plicatilis. The survival rate was determined after 24 h of exposure to PHE. The survival rate of PHE had no effect at a maximum of $300mg\;L^{-1}$. The r was determined after 72 h of exposure to PHE. It was observed that r in the controls (absence PHE) was greater than 0.5, but that it suddenly decreased with an increased concentration of PHE. PHE reduced r in a dose-dependent manner and a significant reduction occurred at a concentration of greater than $37.5mg\;L^{-1}$. The $EC_{50}$ value of r in PHE exposure was $63.7mg\;L^{-1}$. The no-observed-effect-concentration (NOEC) of r in PHE exposure was $18.8mg\;L^{-1}$. The lowest-observed-effect-concentration (LOEC) of r in the PHE exposure was $37.5mg\;L^{-1}$. From the results, the concentration of PHE (greater than $37.5mg\;L^{-1}$) has a toxic effect on the r of B. plicatilis in natural ecosystems. These results(including NOEC, LOEC and $EC_{50}$) might be useful for the Polycyclic aromatic hydrocarbons(PAHs) toxicity assessment in marine ecosystems.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.6
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• pp.511-518
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• 1993

The lifespan and fecundity of three types(ultra small, small and large) rotifer, Brachionus plicatilis, were investigated. Generally, the lifespan and fecundity of three types rotifer were better at $25{\sim}27^{\circ}C$ than at $20{\sim}22^{\circ}C$, and this phenomenon was more distinct in the ultra small and the small type rotifers. With regard to salinity, while the ultra small and the large type rotifer prefer.ed low salinity(16ppt) to high salinity(32ppt), fecundity of the small type rotifer was higher at high salinity(32ppt) than at low salinity(16ppt). Suitable food organisms were Tetraselmis tetrathele and Chlorella ellipsoidea for the three types rotifer. Tetraselmis tetrathele was more adequate for the ultra small and large type rotifer as live food. However, Chlorella ellipsoidea showed better dietary value for the small type rotifer.

• Fisheries and Aquatic Sciences
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• v.8 no.2
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• pp.70-75
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• 2005

We investigated the effects of salinity and three food species of microalgae on the growth of three types of the rotifer Brachionus plicatilis, with the aim of improving mass culture of rotifers in hatcheries. Three types (large, small, and ultra-small) of the rotifer were cultured at 16 ppt and 32 ppt salinity with the green algae Chlorella ellipsoidea, Nannochloris oculata, or Tetraselmis tetrathele. The maximum density and specific growth rate were compared for each rotifer type. Ultra-small rotifers grew significantly faster at 16 ppt salinity than at 32 ppt, and C. ellipsoidea and T. tetrathele promoted significantly higher growth than did N. oculata. However, small rotifers grew significantly better at 32 ppt salinity than at 16 ppt, and small rotifers fed on N. oculata achieved the highest density at 1,185 individuals/ml. Large rotifers grew faster at 16 ppt salinity than at 32 ppt, with a diet of T. tetrathele resulting in the fastest growth. Each type of rotifer thrived under different regimens of microalgae and salinity.