Comparison of variation on gene expression and morphology between wild and cultured Japanese eel (Anguilla japonica)
Date Issued
2008
Date
2008
Author(s)
Chien, Hui-Chun
Abstract
The Japanese eel (Anguilla japonica) is a catadromous fish with a complex life cycle, spending their lives both in sea and freshwater environments. The wild eels hatch in the sea, and the leptocephali are transported from the spawning ground to the continental shelf. They metamorphose into glass eels in the coastal waters then become yellow eels in rivers where they may live for 4–10 years until silvering. After silvering, eels migrate back to the spawning area to spawn and die. In contrast with the wild eels that follow this normal migratory pattern to grow, mature and reproduce, the cultured eels that are collected from the wild spend their whole life cycle in aquaculture farms. In captivity, they grow fast when fed with commercial diet and may reach silver eel stage in two years. This study aims to investigate the differences between wild and cultured eels on morphological indices and pituitary hormone gene expression profiles due to different growth rates and habitats. The morphological indices and pituitary hormone gene expression profiles were compared between wild and cultured eels of the same size range and same developmental stage.ild eels were collected from Kaoping River estuary in southwestern Taiwan from May 1998 through May 2008 and the cultured eels, cultivated about 1-2 years, were collected from Yun Lin , Chiayi , Tainan and Pingdong. Morphological indices like CF, GSI, OI and FI, together with mRNA expression profiles of GPα, FSHβ, LHβ and POMC were examined. The results showed that cultured female eels, with the same size, have higher mean CF and GSI than wild ones. No significant differences were found between males of wild and cultured eels. Irrespective of the sex, mean OI and FI are significantly higher in the wild eels than cultured ones. In pituitary hormones, the expression of GPα, LHβ and POMC mRNA in males were higher in the wild than in the cultured eels. However, no difference on mean FSHβ mRNA expression was found between wild and cultured males. In female eels, there were no significant differences between wild and cultured eels in mRNA expression profiles of GPα, FSHβ, LHβ and POMC. Taken together, the results revealed only that male but not female eels were found to have the consistence aptitude in morphology and endocrine. The cultured eels spend their life in a more stable environment where they do not experience drastic environmental changes like salinity variation, osmotic stress and competition in food. In addition, in the same age eels, cultured eels grow faster than wild eels due to the ample amount of food supplied to them. These conditions may have caused the endocrine and morphological differences between wild and cultured eels.
Subjects
Japanese eels
Cultured eels
Morphologic indices
Gonadotropins
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