Changes
in oocyte and blood plasma osmotic components of ayu, Plecoglossus
altivelis Temminck & Schlegel during oocyte maturation
Ying-Nan
Chen, Shu-Ling Hsieh, Ching-Ming Kuo-2003
Aquaculture
Research, 34(10):
859
Abstract:
Oocyte
maturation in teleosts is characterized by a complex series of cytoplasmic
and nuclear changes. The purpose of this study is to present sequential
changes in the oocyte constituents and regulatory mechanisms involved in the
hydration and osmotic regulation of oocytes during final maturation of ayu, Plecoglossus
altivelis Temminck & Schlegel. Oocyte volumes and water contents in
ayu (P. altivelis) markedly increased from 0.372 mm3
and 60.5% at the mature stage to 0.712 mm3 and 79.4% at the
time of oviposition. In the same period, net increases in total free amino
acids and electrolytes were noted, and involvements of these constituents in
the water uptake by oocytes are discussed. Moderate oocyte hydration in ayu
is accompanied by steady increases in Na+, but not K+,
and these observations are in contrast to results for all other marine
teleosts reported elsewhere. In the present study, a steady increase in
oocyte Na+ during maturation until ovulation pre-dominantly
results from diffusional leakage due to concentration gradients, while at
the time of oviposition, both active transport and diffusional pathways play
important roles in osmotic regulation in ayu oocytes.
(Department of Aquaculture, National Pingtung
University of Science and Technology, 1, Hseuh Fu Road, Nei-Pu Pingtung,
Taiwan 912, ROC. E-mail of Ching-Ming Kuo: cmkuo@mail.npust.edu.tw)