The migration of docosahexenoic acid (DHA) to the developing ovary of female zebrafish (Danio rerio)

Fish selectively reserves docosahexenoic acid (DHA) in ovary during gonadal development. However, no direct proof supports this. The present study tried to elucidate the DHA migration to the developing ovary of female zebrafish. An injection study of C-13-labeled DHA for DHA tracing was conducted, and another injection study of unlabeled-DHA (DHA-injected group) and BSA-saline (control group) was conducted for lipid and DHA content detection, related gene expression analyses, and histological observation. The results showed that the rapid absorption of lipid occurred at stage III with a constant accumulation of DHA in the ovary. The proportion of oocytes at stage III on day 7 and 21, and at stage IV on day 3 and 21 in DHA-injected group was significantly higher than that in control group, respectively (P < .05). The injected C-13-labeled DHA was accumulated twice in the ovary respectively on day 1 and 7, and remained at a relatively high level. In DHA-injected group, the fatp4 expression was significantly higher in ovary on day 3, 5 and 7 (P < .05), and significantly lower (P < .05) in liver on day 5, 14 and in muscle on day 1, 5 and 7 than that in control group. In conclusion, the present study suggested a migration of DHA from the liver and muscle to the gonads when necessary.