Crude oil exposure affects air-breathing frequency, blood phosphate levelsand ion regulation in an air-breathing teleost fish, Hoplosternum littorale

Exposure of a facultative air breather, Hoplosternum littorale, to 12.5, 25 , and 37.5% of the water soluble fraction (WSF) of Urucu crude oil, resulte d in a rapid increase in air-breathing frequency (ABF) sustained over the 4 5 min period of exposure. Following 4 h exposure to a graded increase in WS F up to 50%, there was no significant affect on haematocrit, or plasma [Na] and [K+]. Crude oil ingestion resulted in some degree of ion regulatory i mpairment, however results were variable. A single oral dose of 3.0 ml/kg o f Urucu crude elevated net whole body Na+ efflux and resulted in a 7% reduc tion in plasma [Na+] 72 h following ingestion, A single oral dose of 3.0 ml :kg resulted in a significant net whole body K+ efflux and a reduction in p lasma [K+] 24 h after ingestion. No mortalities were observed in any exposu re regime in this study. An oral dose of Urucu crude oil at 3.0 ml/kg also resulted in a 24% reduction in ATP:Hb ratio (from 0.206 to 0.157) and a 31% reduction in GTP:Hb ratio (0.455 to 0.315) 24 h following ingestion indica ting that these fish may be hypoxemic. Taken together, these results indica te that exposure of H. littorale to Urucu crude oil affects gas exchange an d ion regulation. (C) 1999 Elsevier Science Inc. All rights reserved.