Meeting Abstract

45.5  Thursday, Jan. 5  Vitellogenin gene expression is correlated with stage 2 oogenesis in zebrafish (Danio rerio) CONNOLLY, MH*; DUTKOSKY, RM; HEAH, TP; SAYLER, GS; HENRY , TB; University of Tennessee, Knoxville ; University of Tennessee, Knoxville ; University of Tennessee, Knoxville ; University of Tennessee, Knoxville ; University of Tennessee, Knoxville mconnol3@utk.edu

Vitellogenin genes (e.g., vtg-1) code for egg yolk proteins that are highly induced by estrogen and estrogen mimics. While induction of vtg-1 has been established as a biomarker of exposure to environmental estrogens in male fish, little is known about how its expression relates to the stages of oogenesis in females, especially among fish with asynchronous egg development. The objective of this study was to relate hepatic vtg-1 expression to changes in oocyte and ovarian morphology in adult zebrafish (Danio rerio). Liver and gonad samples were collected from female fish 1-32 days post-spawning and analyzed using qRT-PCR and histological methods. Four stages of oocyte development were distinguished at all time points under investigation. Notably, the composition of these stages within the ovary indicates that zebrafish eggs develop in distinct batches, which may be reminiscent of seasonal spawning behavior observed among wild zebrafish. Vtg-1 was positively correlated with the presence of stage two oocytes, suggesting that it is required during early vitellogenesis. In addition, the greatest upregulation of vtg-1 occurred one hour post-spawning, indicating that the event of spawning itself may be important to the regulation of oocyte development in fish.