EFFECT OF HYPOXIA ON NEUROPEPTIDE GENE EXPRESSION IN CHANNEL CATFISH

Brian Ott*, Peter Allen, and Les Torrans
 
USDA-ARS Warmwater Aquaculture Research Unit
Thad Cochran National Warmwater Aquaculture Center
Stoneville, MS 38776 USA
Brian.Ott@ars.usda.gov
 

Maximizing appetite is critical for intensive production of catfish; a reduction in feed consumption means a longer production cycle with higher mortalities.  When the minimum dissolved oxygen (DO) concentration falls below 3.0 mg/L there is a decrease in feed consumed.  The primary objective of this project was to examine regulation of the neuropeptides urotensin I (UI) and corticotropin-releasing factor (CRF) during a short bout of hypoxia that replicated the daily conditions of a catfish production pond.  Dissolved oxygen concentration was maintained in control aquaria at 95% saturation.  Hypoxia tanks were maintained at 95% saturation, dropped to 20% saturation for 12 hours then returned to saturation in replicate aquaria.   Fish were sampled at 0, 6, 12, 18, and 24 hours.  Venous PO2 was the same after 6 hours of hypoxia, 60% lower in the hypoxia group after 12 hours of hypoxia, and the same 6 hours after the DO returned to saturation.  Gene expression for CRF did not significantly change during hypoxia at any measured time point.  There was a significant increase in Urotensin I gene expression (1.6-fold higher) in the hypoxia group 18 hours after the onset of the experiment but fell to pre-hypoxia level by 24 hours.  At the time points sampled, the anorectic neuropeptide UI was significantly upregulated six hours after a 12-hour bout of hypoxia.  This data suggests that urotensin I may act to decrease appetite after periods of hypoxia.