• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.2
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• pp.160-163
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• 2001

This study was performed to investigate the effect of vitamin $B_{12}$ addition on the production and hatching rate of resting egg of freshwater rotifer, Brachionus calyciflorus. Different concentrations of vitamin $B_{12}$ was added into concentrated freshwater Chlorella before fed to rotifer and rotifer was cultured in 250 mL flask. The maximum density of rotifer was 138 inds./mL at 6 ppm and it increased with an increase of vitamin $B_{12}$ addition. Mixis rate and fertilization rate of rotifer were $63.0\%$ and $89.6\%$, respectively, at 6.0 ppm. The production of resting eggs per mL was 231 eggs/mL at 1.5 ppm, but there was no significant difference among vitamin $B_{12}$ addition levels. The highest production of resting eggs per 10,000 rotifers and Chlorella dry weight (g) were 11,289 eggs and 121,252 eggs, respectively, at the 6 ppm. The hatching rate of resting egg was not significantly different among vitamin $B_{12}$ addition levels, but significantly higher than the control (without addition of vitamin $B_{12}$ ). These results showed that vitamin $B_{12}$ addition could affect production and hatching rate of resting egg of freshwater rotifer, B. calyciflorus.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.5
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• pp.779-784
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• 1998

The specific growth rate and production of resting ega of the freshwater rotifer, Brachionus calyciflorus Pallas was investigated at the different temperatures ($20\~30^{\circ}C$). The rotifer was cultured in 250 ml flask and fed on concentrated freshwater Chlorella. Specific growth rate of B. calyciflorus showed higher rate at higher temperature, but maximum density was observed higher at lower temperature, expect at $20^{\circ}C$. The production of resting egg with temperature was showed decrease on the basis on $26^{\circ}C$. The highest number of resting egg per ml and rotifer $10^4$ were 157 eggs and 810 eggs at $26^{\circ}C$, respectively. This result shows that the optimum temperature for mass culture and resting egg production of this freshwater rotifer were $30^{\circ}C$ and $26^{\circ}C$, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.62-67
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• 2019

We studied the effect of several sex-related steroid hormones (serotonin, progesterone and ${\beta}$-estradiol) for 6 days on the induction of sexual reproduction for the mass production of resting eggs in the marine rotifer Brachionus rotundiformis. The highest mix rate of 20.6% appeared with the ${\beta}$-estradiol ($E_2$) treatment on the third day. The number of resting eggs was highest with $E_2$ treatment, followed by that of the serotonin treatment group. In addition, we investigated the effect of the hormones on the expression pattern of the genes related to sexual reproduction in the rotifer. NrbP, SRY, Cyclin and MrpmB genes were up-regulated with all the hormone treatments. As a result, ${\beta}$-estradiol was more effective than the other hormone treatments to produce resting eggs in B. rotundiformis. We suggest that the sexual reproduction-related genes in the rotifer are the NrbP, SRY, Cyclin and MrpmB genes. Further study is required to determine the optimum concentration of $E_2$ for the effective production of resting eggs in the rotifer.

• 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 ($46.4\%$).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.692-697
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• 2016

This study examined the effects of salinity and medium used on the induction of sexual reproduction for the mass production of the resting eggs in the marine rotifer Brachionus rotundiformis for 9 days. After exposure to various salinities, the mixis rate in all treatments began to increase on the third day and decreased after the 4th or 5th day. The resting eggs appeared on the 4th day at 10‰, 15‰, 20‰, 25‰. In particular, the fertilization rates with 33.3% and 31.3% at 20‰ and 25‰ on day 6 were higher than those of the others, respectively. Mean mixis rate for 9 day at 0‰ and 20‰ were the highest with 25.3% and 20.2%, respectively, and the fertilization rate (14.0%) at 25‰ was the highest. In the medium experiment used, the mixis rate in all treatments were similar to the results of the salinity experiment. The resting eggs were only found at 0% and 25% of the used medium treatments. While there were no significant differences in the mean fertilization rate of all treatments, the mean mixis rate (22.3%) in the 25% treatment was higher than that of the control (0% treatment). As a result, salt stress was more effective than using the used medium to induce sexual reproduction in B. rotundiformis. The optimal salinity was considered to be 20-25‰, which caused a high mixis and fertilization rate in the rotifer. These results provide basic data for the mass production of rotifer resting eggs.

• Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.57-62
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• 2012

Interspecific relationship between a euryhaline rotifer Brachionus rotundiformis and a cyclopoid copepod Apocyclops borneoensis was investigated in the laboratory culture. In a mixed culture of B. rotundiformis and A. borneoensis, population growth of B. rotundiformis was suppressed from day 10, while growth in a monoculture population continuously increased throughout the experimental period. However, the population growth of A. borneoensis in the mixed culture did not markedly differ from that in a monoculture population. Suppression of B. rotundiformis growth coincided with a decrease in the numbers of both non-egg-bearing and egg-bearing females, and increasing resting egg formation. Growth of A. borneoensis was not affected by the presence of the rotifer. However, relative growth index of ovisac bearing females in the mixed culture was 1.62 times higher than that in the monoculture. Presence of the copepod did not greatly reduce the food available to the rotifer population. The rotifer B. rotundiformis responded in a unique way, to stresses such as physical damage (filtering by A. borneoensis) with the production of many resting eggs to increase its chances of survival.

• Korean Journal of Veterinary Research
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• v.31 no.1
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• pp.33-40
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• 1991

For the observations of both the membrane properties and the excitability on the unfertilized eggs of female mice, changes of the membrane resistance and the membrane potential by hyerpolarizing current stimulation were recorded. As current-voltage relation was linear over the entire range (-180mV~+60mV), membrane resistance($R_m$) was calculated from the amplitude of electrotonic potential to a given stimulus current. Also the presence of anode-break excitation was confirmed. The results were as follows; 1. There was a linear relation between the membrane resistance and resting membrane potential, the expected input resistance was 61. 4M$\Omega$(resting membrane potential was $-18.9{\pm}8.7mV$, mean${\pm}$SD, n=30). 2. Transient depolarization with overshoot was generated just after hyperpolarizing current stimulus and showed the dependency of stimulus duration. 3. Transient depolarization lasted over 30ms, amplitude of these depolarization was increased by high $Ca^{{+}{+}}$(20mM) and inhibited by $Ca^{{+}{+}}$-antagonist, $Mn^{{+}{+}}$. 4. From the above results, it was suggested that the unfertilized mouse egg showed the characteristics of the excitable cell.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.225-229
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• 2000

This study was performed to investigate production and hatching rate of the resting egg of freshwater rotifer, Brachionus calyciflorus fed the 5 different diets (ESP, freshwater Chlorella, baker's yeast, the mixture off$70{\%}\;ESP\;and\;30{\%}$freshwater Chlorelia, and the mixture of $30{\%}$ baker's yeast and $70{\%}$ freshwater Chlorella). The highest productions of resting eggs were 123.3 egg/ml and 126.7 egg/ml in the mixture of $70{\%}$ ESP and $30{\%}$ freshwater Chlorella, and the mixture of $30{\%}$ baker's yeast and $30{\%}$ and $70{\%}$ freshwater Chlorella, respectively, which were significantly better than ESP, freshwater Chlorella or baker's yeast alone (P<0.05). Hatching rate of the resting eggs from rotifer fed the mixture of $70{\%} ESP\;and\;30{\%}$ freshwater Chlorella was the highest, $71.9{\%}$ although this value was not significantly different compared with the mixture of $30{\%}$ baker's yeast and $70{\%}$ freshwater Chlorella, and freshwater Chlorella (P^lt;9.05). The results showed that the mixture of baker's yeast or ESP with the freshwater Chlorella seemed to be the best feeding regime for the production and hatching rate of resting egg of freshwater rotifer.

• Korean Journal of Veterinary Research
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• v.29 no.3
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• pp.245-251
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• 1989

In order to manifest the presence of Na-K pump and its property on the unfertilized egg membranes of mouse, membrane potential was recorded under the physiological condition (at $37^{\circ}C$ and 4mM $Ca^{2+}$). After an induction of superovulation, the fresh eggs with zona pellucida were collected from mouse oviduct. Transient hyperpolarization as pump action was recorded after the switch into the high potassium perfusate (15mM $K^+$) from K-free perfusate, and the difference between membrane potential observed just before the perfusion of high potassium solution and the maximal membrane potenlial during the perfusion of high potassium solution was regard as pump activities. The results observed were as follows, 1. Resting mombrane potential was depolarized under the treatment of $10^{-5}M$ ouabain. 2. Pump activities of the unfertilized mouse eggs were $-3.38{\pm}0.61mV$ ($Mean{\pm}SD$, n=6), recorded as transient hyperpolarization due to the electrogenic property. 3. Pump activities were blocked by both treatment of $10^{-5}M$ ouabain and perfusion of Nafree solution, while increased by high $Na^+$ (300mM) perfusion ($-7.45{\pm}0.75mV$, n =2). 4. Hyperpolarization due to pump activity was not altered by $Mn^{2+}$. 5. Above results confirm the presence of ouabain-sensitive Na-K pump, which affected the membrane potential directly, on the unfertilized egg membranes of mouse.

• Journal of Sericultural and Entomological Science
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• v.18 no.1
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• pp.7-10
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• 1976

This experiments were carried out to know hatching power on treatments of cold temperature and hydrochioric acid Iron Late January to Early February. Used silkworm variety was Jam 103${\times}$ Jam 104 laying in Spring. The results may be summarized as follows: 1. The resting of silkworm eggs activated to Late January, to longer cold treatment was, the more effects of activating increased completely. So activated eggs were possible to incubation. 2. How to the light or short hours of hycrochloric acid were compare with heavy or long each other, it was inclined that the former seems to be worse than the latter. 3. On the interaction of cold treatments and hydrochloric acid, in case of short cold treatment, hatching power was better effect all treatments of hydrochloric acid than control, but no difference between specific gravity or treatment hours. On tile contrary, in case of more longer of cold treatments, hatching power depended not only upon the specific gravity, but also upon the treatment hours.