Differential Expression of Hypothalamic and Gill- System With Osmotic Stress in the Euryhaline Black Porgy, .

The local gill production of corticotropin releasing hormone () and -receptor () is hypothesized to play important roles during seawater (SW) and freshwater (FW) acclimation in euryhaline black porgy (). The mRNA expression of , , and / () was examined in SW and FW diencephalon (Dien) and in the gills at different exposure time by Q-PCR analysis. The hybridization results indicate that mRNA hybridization signals were more abundant in FW fish in the gigantocellular (PMgc) and parvocellular (PMpc) part of the magnocellular preoptic nucleus versus SW fish. The and expressing cells were located in basal cells of gill filament. Furthermore, dexamethasone (DEX) treatment could increase the -system in the gill. Increased transcripts of the -system in the gill via and CRH treatments suggest that CRH may regulate the system in a local manner. The a-Nka cells were localized in the filament and secondary lamellae mitochondria rich cells (MRCs) of FW fish at 8 h and 1 day. a-Nka cells were seen in both filament and lamellae in the FW but much less in SW fish indicating that gills play key roles in black porgy osmoregulation. Gill and play important roles in the response to salinity stress.