• 한국수산과학회지
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• 제44권6호
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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.

• Ocean and Polar Research
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• 제40권4호
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• pp.213-222
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• 2018

We investigated seasonal variations in the abundance of the adults and the resting eggs of copepods to understand the role of copepod resting eggs for maintaining their population inhabiting the coastal area of Dadaepo, Korea. Adults and resting eggs of copepods were collected bi-monthly with a conical net (45 cm mouth diameter, $330{\mu}m$ mesh size) and van Veen grab ($0.1m^2$ area), respectively, from October 2016 to September 2017. The species of resting eggs were identified using mtCOI gene. The mean abundance of copepods was highest in October ($3686{\pm}1190inds{\cdot}m^{-3}$) and lowest in January ($176{\pm}60inds{\cdot}m^{-3}$) with the dominance of Paracalanus parvus s.l.. Among copepod producing resting eggs, Acartia omorii and Centropages abdominalis were dominant. The mean abundance of resting eggs was the highest in July ($9148{\pm}6787eggs{\cdot}m^{-2}$) and the lowest in October ($530{\pm}348eggs{\cdot}m^{-2}$). Most of the collected resting eggs were identified as A. omorii's. The mean abundances of A. omorii adults and resting eggs were highest in July, and both abundances fluctuated in a similar pattern except in September. In September, A. omorii adults were observed in a state of low abundance, while their resting eggs occurred in a state of high abundance. These results suggest that A. omorii maintain their population by producing a large quantity of resting eggs, particularly diapause eggs, before the seawater temperature rises. These eggs would hatch and be newly recruited to their population when the environmental condition becomes favorable.

• Journal of the korean society of oceanography
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• 제37권3호
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• pp.108-115
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• 2002

To Investigate the distribution of resting eggs at the intertidal zone, Gomso Bay, samples were taken from the top of the sediments to 10 cm depth at four sites using a cylindrical corer in February, 1997. Additional samples were also taken from one station at subtidal zone to compare the distributions between the inter- and subtidal zones. The resting eggs of few copepods, Acartia pacifica, Centropages abdominalis, Calanopia thompsoni, and Tortanus forcipatus were studied. Mostly, the abundance of the resting eggs in the lower intertidal zone was greater than that in the upper intertidal zone, but was not significantly different from that in the subtidal zone. The abundance of the resting eggs in the intertidal sediments was related with the grain-size and moisture content of sediments. Intertidal sediments are potential egg banks like subtidal sediments.

• 한국양식학회지
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• 제9권4호
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• pp.321-327
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• 1996

Production of resting egg from the Korean rotifer, Brachiunus plicatilis (L and S-type) was investigated at different temperatures (L-type : 20, 24, $28^{\circ}C$, S-type : 28 32, $36^{\circ}C$) and salinities (10, 20,30 ppt). The rotifer was cultured in 25 ml test tube and fed on Nannochloris oculata. With regard to mixis rate, L-type rotifer showed higher rate at lower temperature, and the highest rate was observed at 20 ppt of salinity at each temperature of the experiment. However, for S-type rotifer, the optimum temperature and salinity were $28\~32^{\circ}C$ and 20 ppt, respectively. The highest number of resting egg was 173 eggs/ml in 16 days at $24^{\circ}C$, 10 ppt for L-type rotifer and 410 eggs/ml in 14 days at $28^{\circ}C$, 10 ppt for S-type rotifer. The maximum number of resting egg produced per 10,000 rotifers was 8,122 eggs at $20^{\circ}C$, 20 ppt for L-type rotifer and 8,700 eggs at $28^{\circ}C$, 20 ppt for S-type rotifer. The maximum number of resting egg produced $10^8$ cells of N. oculata was 50.7 eggs for L-type rotifer ($24^{\circ}C$, 20 ppt) and 79.6 eggs for S-type rotifer ($32^{\circ}C$, 10 ppt). The number of resting egg produced per day was $1\~11$ eggs/ml for L-type rotifers and $21\~35$ eggs/ml for S-type rotifer in 9 combination experiments. In this study, S-type rotifer is better than L-type rotifer in resting egg production, and the optimum temperature and salinity for resting egg production were $20^{\circ}C$, 20 ppt for L-type rotifer and $28^{\circ}C$, 20 ppt for S-type rotifer. This result shows the difference of Korean rotifer in the optimum condition for resting egg production from other rotifers reported earlier.

• Fisheries and Aquatic Sciences
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• 제3권2호
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• pp.126-134
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• 2000

We investigated the distribution of the marine cladoceran resting eggs in the intertidal sediments of Gomso Bay, Korea and compared the data with those in the subtidal sediments. The abundance of the eggs in the top 6cm of the sediments was higher than that in the other depths. The abundances of the eggs in seaward intertidal sediments below mean sea level (MSL) were higher than those in the sediments over MSL, but were not significantly different from those in the subtidal sediments. The distribution of the resting eggs of cladocerans in the intertidal sediments was affected by the grain-size and moisture content of sediments. The results of the present study suggest that the intertidal sediments as well as the subtidal sediments are a potential egg bank which plays important roles in population dynamics of zooplankton in coastal waters, in particular, recruitment of eggs into plankton.

• 한국양식학회지
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• 제12권1호
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• pp.31-38
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• 1999

넙치(Paralichthy olivaceus) 및 돌돔 (Oplegnathusfasciatus) 자어를 대상으로 각각 B.plicatilis와 B.rotundiformis의 내구란에서 갓 부화한 rotifer의 먹이효율과 지방산 조성을 대량배양한 rotifer와 비교 조사하였다. Rotifer 내구란은 Chlorella와 빵 효모를 먹이로 공급하여 $1~4m^3$에서 생산하였다. B.plicatilis와 B.rotundiformis 내구란은 $5^{\circ}C$ 암내장 상태에서 각각 3개월과 5개월 동안 보관하여 $28^{\circ}C$ 연속 조명하에서 부화시켰다. 내구란에서 갓 부화한 rotifer와 대량 배양한 rotifer(대조구)를 자어에게 공급하였다. B.rotundiformis 내구란에서 갓 부화한 rotifer를 공급한 돌돔자어의 성장과 생존률은 대조구와 비슷하였게 나타났고, B.plicatilis 내구란에서 갓 부화한 rotifer를 먹은 넙치자어의성장과 생존률은 각각 대조구에 비해 비슷하거나 높게 나타났다. 또한 내구란에서 갓 부화한 rotifer의 지방산조성은 대조구와 비슷하게 나타났다. 이와 같은 결과를 볼 때 내구란에서 갓 부화한 rotifer는 넙치 및 돌돔 자어의 먹이로서 이용 가능하다고 판단된다.

• 한국양식학회지
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• 제18권2호
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• pp.115-121
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• 2005

본 연구는 통기방법과 배양수의 환수에 따른 담수산 rotifer B. calyciflorus의 내구란 형성을 조사하였고 0.5 톤 수조에서 내구란 대량 생산을 수행하였다. 산소와 공기를 공급한 실험구에 있어서 rotifer의 최고밀도와 유성생식률은 차이는 없으나 수정률과 내구란 형성은 공기를 공급한 실험구가 산소를 공급한 실험구보다 높게 나타났다. 배양수의 환수간격에 따른 실험에서 환수를 하지 않은 실험구가 rotifer 최고밀도와 내구란 형성은 환수를 한 실험구(매일 환수한 실험구)보다 높게 나타났지만 내구란 생산의 효율적인 측면에서 Chlorella 건조중량당 내구란 형성은 환수를 한 실험구(매일 환수한 실험구)에서 가장 높게 나타났다. 또한 0.5톤 수조에서 내구란의 총 생산량은 $51.8{\sim}57.9{\times}10^6$개로 나타났다. 본 연구의 결과를 종합하여 볼 때, 공기를 공급한 batch 배양이 담수산 rotifer, B. calyciforus의 내구란을 대량생산하는데 효과적인 방법인 것으로 판단된다. 또한 이종의 내구란 대량생산은 해수산 rotifer B. plicatilis와 B. rotundiformis와 비슷한 생산 효율을 보인 것으로 판단된다.

• 한국양식학회지
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• 제9권4호
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• pp.345-351
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• 1996

한국산 B. plicatilis, L-type rotifer와 S-type rotifer의 내구란 대량생산은 L-type rotifer의 경우 15일 동안 농축 Chlorella + 빵효모 혼합구와 빵효모 단독구로 하였고 S-type rotifer는 7일동안 1 $m^3$ 수조에서 농축 Chlorella로, $6{\~}8$일 동안 4 $m^3$ 수조에서 냉동 농축 Chlorella + 빵효모로 대량생산하였다. L-type rotifer 내구란 대량생산 실험에서 농축 Chlorella + 빵효모 혼합구가 총 내구란 생산 $54.5{\times}10^6$개, $10^{8}$ rotifers 당 내구란 생산 $30.5{\times}10^6$개, 먹이 건조 중량 1g 당 내구란 생산 $100{\times}10^3$개로 빵효모 단독구 보다 높게 나타났다. S-type rotifer의 내구란 대량생산은 4 $m^3$ 수조에서 냉동 농축 Chlorella + 빵효모를 먹이로 총 내구란 생산 $149{\~}567{\times}10^6$개, $10^{8}$ rotifers당 내구란 생산 $36{\~}123{\times}10^6$개, 먹이 건조 중량 1 g당 내구란 생산 $131{\~}338{\times}10^3$개를 생산하여 1 $m^3$ 수조에서 농축 Chlorella를 단독 먹이로 생산한 경우 보다 높았다.

• The Korean Journal of Physiology
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• 제23권1호
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• pp.35-42
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• 1989

The present study was performed to observe the effects of cations on resting membrane potential and pump activity in the unfertilized eggs of ICR strain mice. After an induction of superovulation, the fresh eggs with zona pellucida were collected and the membrane potentials were recorded. Recordings of membrane potential in this study was obtained from the physiological conditions ($37^{\circ}C$ and 4mM Ca in standard solution), differently from the another reports with unphysiological conditions (room temprature and high Ca in standard solution) for a stable and long-lasting observations. Presented data was obtained within 6 hours after collection from the oviduct. The results observed are as follows, 1) Resting potential of the unfertilized eggs was $-25.8{\pm}3.8mV$ $(Mean{\pm}Se,\;n=31)$. 2) As the K ion concentration was increased, resting membrane potential was depolarized but showed hyperpolarization with $K^{+}$ below 25mM. 3) Alteration of the resting membrane potential for the changes of $Na^{+}$ concentration were hardly observed, while resting potential was hyperpolarized as $Ca^{2+}$ concentration was increased. 4) Pump activity as transient or prolonged hyperpolarization was $-2.29{\pm}0.75mV$ $(Mean{\pm}Se,\;n=16)$, the hyperpolarization was increased in both amplitude and duration under the 10mM $Ca^{2+}$ solution. 5) Hyperpolarization due to pump activity was decreased or disappeared by $5{\times}10^{-5}\;M$ ouabain treatment and could not be observed under the both Na-free and Ca-free solutions. 6) Above results are likely to suggest that the resting potential of the mouse unfertilized eggs is affected to mainly by Ca-dependent K conductance and Na-Ca exchange mechanism and that there is pump activity coupling between $K{+}$, $Na^{+}$ and $Ca^{2+}$.

• 한국양식학회지
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• 제9권4호
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• pp.329-337
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• 1996

한국산 rotifer, B. plicatilis, S-type를 대상으로 식물부유생물, 농축 Chlorella 및 효모류에 대한 내구란 생산과 먹이 종류에 따라 생산된 내구란의 부화율을 조사하였다. 4 종류(Chlorella ellipsoidea, Nannochloris oculata, Tetraselmis suecica, Pavlova lutheri) 가운데 N. oculata는 3,760개/20 ml로 가장 많은 내구란을 생산하였다. 그러나 식물부유생물 종류에 따른 부화율의 유의적인 차이는 없었다. 9 종류의 농축먹이(유지효모, 빵효모, 두 종류의 해수산 농축 냉장 Chlorella, 해수산 냉동 Chlorella, 냉동 해수산 Chlorella ($70\%$)+ 빵효모($30\%$), 냉동 해수산 Chlorella ($30\%$)+ 빵효모($70\%$), 두 종류의 냉장 담수산 Chlorella)에서 내구란 생산이 가장 많은 먹이는 냉동 Chlorella($30\%$)+빵효모($70\%$)와 냉장 담수산 Chlorella에서 각각 283개/ml로 나타났다. Rotifer $10^4$개체와 건조 먹이 1 mg당 내구란 생산은 냉동 Chlorella ($30\%$)+빵효모($70\%$)에서 각각 5,566개와 2,131개로 가장 높게 나타났다. 농축 먹이에 따른 내구란의 부화율은 유지효모가 $67.4\%$로 가장 높았다. 본 연구의 결과, 경제적인 내구란 생산을 위하여 빵효모와 농축 냉동 Chlorella를 혼합하여 공급하는 것이 효과적인 것으로 판단된다.