Cortical reaction and solicitation mechanism in Hemibarbus labeo ovum |
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Authors: | Gan Guangming and Zhang Yaoguang |
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Institution: | (1) College of Life Science, Southwest Normal University, Chongqing, 400715, China;(2) Genetics Research Center, Southeast University, Nanjing, 210009, China |
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Abstract: | There are 1 to 4 rows and five types of cortical alveoli in the cortex of the pallas (Hemibarbus labeo) egg. From the outer to the inner of the cortex, the diameter of the cortical alveoli decreases gradually. We found a new
structure named solicitation speckle at the low latitude of the animal pole and near the micropylar apparatus between the
ovum envelope and cell membrane in the zygote of fish. The solicitation speckle similar to type I cortical alveoli was very
purple in H.E. chromosome, and it had no obvious boundary with the ovum envelope and membrane. Moreover, no membrane around
the solicitation speckle in TEM was found. In SEM, the solicitation speckle looked flocculent. During cortical reaction, the
solicitation speckle played a very important function in arousing cortical reaction. Thirty-five seconds after fertilization,
cortical alveoli began to break down near the low latitude of the animal pole. At the same time, the same thing happened near
the micropylar apparatus before cortical reaction. Both starting points encountered and healed up at the vestibule of the
micropylar apparatus. The cortical reaction that happened near the low latitude of the animal pole was another new pattern.
The cortical reaction was divided into four parts that included latent period, developmental period, climactic period and
declining period. In the latent period, no cortical alveoli were released. In the developmental period, a few cortical alveoli
were released outside the cortex. In the climactic period, several cortical alveoli were inosculated into a big vesicle and
released intensely. In the declining period, the type V cortical alveoli and the other remnant cortical alveoli were released.
Five minutes after fertilization, cortical alveoli were released entirely in the animal pole. Five minutes after fertilization,
all of the remnant cortical alveoli were released. This leads us to conclude that cortical reaction is induced by type I cortical
alveoli, and the solicitation speckle is a volcanic chain reaction under water or the other lower osmotic pressure of fluids.
The outer cortical reaction can accelerate the inner cortical reaction. While cortical alveoli releases in batches, the cell
plasma membrane is reorganized over and over. No cortical alveoli were found below the micropylar tube where sperm enters
the ovum, which suggests that the cortical reaction prevents polyspermy.
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Translated from Acta Hydrobiological Sinica, 2005, 29(5): 479–487 译自: 水生生物学报, 2005, 29(5): 479–487] |
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Keywords: | Hemibarbus labeo cortical alveoli cortical reaction solicitation speckle solicitation mechanism |
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