MEPS 259:253-261 (2003)  -  doi:10.3354/meps259253

Salinity preference of silvering Japanese eel Anguilla japonica: evidence from pituitary prolactin mRNA levels and otolith Sr:Ca ratios

Yu San Han1, John Yu Lin Yu2, I Chiu Liao3, Wann Nian Tzeng1,*

1Institute of Zoology, College of Life Science, National Taiwan University, Taipei, Taiwan, ROC
2Endocrinology Laboratory, Institute of Zoology, Academia Sinica, Taipei, Taiwan, ROC
3Taiwan Fisheries Research Institute, 199 Hou-Ih Road, Keelung, Taiwan, ROC
*Corresponding author. Email:

ABSTRACT: The salinity preference of Japanese eel Anguilla japonica during silvering was validated from the viewpoints of physiological ecology by examining the pituitary prolactin (PRL) mRNA expression and the otolith strontium:calcium (Sr:Ca) ratios of the eels of different sexual maturity stages collected in an estuary of Taiwan. The PRL possessed a putative signal peptide of 24 amino acids and a mature peptide of 185 amino acids. RT-PCR and real-time quantitative PCR analyses indicated that the transcript levels of PRL mRNA significantly decreased from yellow to silver stage. On the contrary, the Sr:Ca ratios at the otolith edge of silver eels, which recorded their latest experience of salinity history, significantly increased. The increase in otolith Sr:Ca ratios and the decrease in PRL mRNA expression are consistent with the timing of migration from freshwater to seawater during silvering of the eel.


KEY WORDS: Japanese eel · Salinity preference · Otolith · Sr:Ca ratio · Prolactin · mRNA · Silvering


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