T6 AM Environmental Hypoxia
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 324-326

(BRO-1117-841086) Changes in gene expression and reproduction in grass shrimp, Palaemonetes pugio, in response to chronic and intermittent hypoxia.

Brouwer, M¹, Brown-Peterson, N¹, Manning, S¹, Larkin, P², , N, Denslow, N³, ¹ University of Southern Mississippi, Ocean Springs, MS² EcoArray LLC, Alachua, FL³ University of Florida, Gainesville, FL

ABSTRACT- Despite the ecological importance of hypoxia, little is known about the sublethal effects of chronic hypoxia on estuarine organisms, and there are no indicators for recognizing populations that are suffering from chronic hypoxic stress. Here we examine the use of hypoxia-responsive gene expression profiles in the grass shrimp, Palaemonetes pugio, as early warning signals of impacts of hypoxia. We cloned 78 potential hypoxia-responsive genes using PCR-select subtractive hybridization. The cDNAs were used to construct macroarrays. Next we exposed grass shrimp to chronic and intermittent hypoxia in a flow-through system and examined effects on gene expression and reproduction. Additionally, gene expression profiles and reproductive parameters were evaluated in wild grass shrimp collected from diurnally hypoxic and normoxic field sites across a large range of spatial and temporal scales. Changes in gene expression profiles are dependent on DO levels and length of exposure. When exposed to 1.5 ppm DO, genes encoding proteins involved oxygen transport and ATP synthesis are upregulated on a time scale of days. Transcription of mitochondrial genes (16S rRNA, cytochrome b and cytochrome c oxidase subunits 1 and 3) and genes involved in heme/iron metabolism are upregulated after 7 days, followed by a coordinated downregulation of the same genes after 14 days. Grass shrimp collected in diurnally hypoxic marsh sites in Pensacola Bay show similar downregulation of mitochondrial gene transcription, whereas shrimp from normoxic controls sites do not. Chronic hypoxia increases fecundity. Diurnal hypoxia decreases fecundity and increases brood interval. Percent gravid females are lower in diurnally hypoxic field sites compared to normoxic sites. These results suggest that hypoxia-responsive macroarrays might be useful for monitoring effects of hypoxia in estuarine crustacea and that it might be possible to link these molecular signals to reproductive fitness. Supported by EPA-STAR Grant R 82945801.

Key words: Hypoxia, Gene Arrays, Reproduction