Resumen del trabajo presentado en la Broodstock Management and Egg & Larval Quality. A Scienc... more Resumen del trabajo presentado en la Broodstock Management and Egg & Larval Quality. A Science in Aquaculture International Conference, celebrada en Stirling (Escocia), en julio de 1992Five females having body weights between 2.133 - 3.291 Kg. were investigated over a two week period to study the ovulatory cycles. When the first ovulation began, each female was handstripped every day, the eggs collected and fertilised using sperm of the two males. The percentage rates of fertilisation and hatching were calculated every time. The results demonstrated that freshly-ovulated eggs showed a 90% fertilisation or greater, and acceptable hatching rateo Ovulated eggs retained in the ovary for one or more days presented a loss of fertilisation and 0% hatching. Three of the five females showed regular three-days ovulatory cycles. In the other two females very few eggs were colleeted and they showed no evidence of constant ovulatory rhythms. Blood samples were taken every day to study the relationship between the ovulatory cycles and the plasmatic changes of sex steroid (17beta-estradiol, testosterone, 17alfa-hydroxyprogesterone and 170', 20{3-dihydroxy-4-pregnen-3-one)
Maximum reproduction rates (G = 0.7–0.8 day−1) of a wild type and two isolated clones of a local ... more Maximum reproduction rates (G = 0.7–0.8 day−1) of a wild type and two isolated clones of a local strain of Brachionus plicatilis were obtained at salinities of 4 and 10‰ Above optimum salinity, reproduction rates decreased by half for each 10‰ increase in salinity. Rotifer density depended on salinity and food concentration. An average density of 1500 rotifers m1−1 was obtained in cultures maintained at a salinity of 20‰ where rotifers were fed on Chlorella stigmatophora at a concentration adjusted to rotifer density. Rotifers transferred from lower (20‰ or 30‰) to higher salinities (30‰ or 40‰, respectively) reproduced at a rate which accorded with the salinity of their new environment. It is suggested that reliable production of B. plicatilis rotifers could be obtained by using mutants incapable of undergoing mixis, such as our clone N.R.E., in combination with cultures maintained at salinities lower than that of sea water (40‰).
A small-scale modular system was developed using stepwise up scaling of rotifer cultures from Ehr... more A small-scale modular system was developed using stepwise up scaling of rotifer cultures from Ehrlenmeyer flasks holding 2-litre culture volumes to 180 litre cultures in cylindrical tanks equipped with an outlet from a conical bottom. Rotifers of an asexually reproducing clone, isolated in our laboratory, were cultured in tanks with sieved, aerated, natural sea water and fed on bakers' yeast at a temperature of 25–27° C. Cultures attained rotifer densities ranging from 200 to 500 rotifers per ml (rot. M1−1), resulting in an average production of 70 rot. M1−1 day−1. This system allows for versatile planning of operating units in accordance with the demands of the hatchery.
... Besides in-dicating the best combination of salinity and food concentration for obtaining lar... more ... Besides in-dicating the best combination of salinity and food concentration for obtaining large numbers of resting eggs, they revealed the contribution of internal population factors that ... A laboratory culture of Brachionus plicatilis was used throughout the experiments. ... Page 6. ...
Resumen del trabajo presentado en la Broodstock Management and Egg & Larval Quality. A Scienc... more Resumen del trabajo presentado en la Broodstock Management and Egg & Larval Quality. A Science in Aquaculture International Conference, celebrada en Stirling (Escocia), en julio de 1992Five females having body weights between 2.133 - 3.291 Kg. were investigated over a two week period to study the ovulatory cycles. When the first ovulation began, each female was handstripped every day, the eggs collected and fertilised using sperm of the two males. The percentage rates of fertilisation and hatching were calculated every time. The results demonstrated that freshly-ovulated eggs showed a 90% fertilisation or greater, and acceptable hatching rateo Ovulated eggs retained in the ovary for one or more days presented a loss of fertilisation and 0% hatching. Three of the five females showed regular three-days ovulatory cycles. In the other two females very few eggs were colleeted and they showed no evidence of constant ovulatory rhythms. Blood samples were taken every day to study the relationship between the ovulatory cycles and the plasmatic changes of sex steroid (17beta-estradiol, testosterone, 17alfa-hydroxyprogesterone and 170', 20{3-dihydroxy-4-pregnen-3-one)
Maximum reproduction rates (G = 0.7–0.8 day−1) of a wild type and two isolated clones of a local ... more Maximum reproduction rates (G = 0.7–0.8 day−1) of a wild type and two isolated clones of a local strain of Brachionus plicatilis were obtained at salinities of 4 and 10‰ Above optimum salinity, reproduction rates decreased by half for each 10‰ increase in salinity. Rotifer density depended on salinity and food concentration. An average density of 1500 rotifers m1−1 was obtained in cultures maintained at a salinity of 20‰ where rotifers were fed on Chlorella stigmatophora at a concentration adjusted to rotifer density. Rotifers transferred from lower (20‰ or 30‰) to higher salinities (30‰ or 40‰, respectively) reproduced at a rate which accorded with the salinity of their new environment. It is suggested that reliable production of B. plicatilis rotifers could be obtained by using mutants incapable of undergoing mixis, such as our clone N.R.E., in combination with cultures maintained at salinities lower than that of sea water (40‰).
A small-scale modular system was developed using stepwise up scaling of rotifer cultures from Ehr... more A small-scale modular system was developed using stepwise up scaling of rotifer cultures from Ehrlenmeyer flasks holding 2-litre culture volumes to 180 litre cultures in cylindrical tanks equipped with an outlet from a conical bottom. Rotifers of an asexually reproducing clone, isolated in our laboratory, were cultured in tanks with sieved, aerated, natural sea water and fed on bakers' yeast at a temperature of 25–27° C. Cultures attained rotifer densities ranging from 200 to 500 rotifers per ml (rot. M1−1), resulting in an average production of 70 rot. M1−1 day−1. This system allows for versatile planning of operating units in accordance with the demands of the hatchery.
... Besides in-dicating the best combination of salinity and food concentration for obtaining lar... more ... Besides in-dicating the best combination of salinity and food concentration for obtaining large numbers of resting eggs, they revealed the contribution of internal population factors that ... A laboratory culture of Brachionus plicatilis was used throughout the experiments. ... Page 6. ...
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