Effects of inorganic mercury on the respiration and the swimming activity of shrimp larvae, Pandalus borealis

In order to test the sensitivity of respiration (physiological and potentia l) to mercury (Hg) contamination, larval shrimp Pandalus borealis were expo sed to inorganic Hg (0-160 ppb) for 27 h in the laboratory. Oxygen consumpt ion rates (RO2), potential respiration (determined by respiratory electron transfer system activity, ETSA), protein content, and swimming activity for zoeae III and zoeae V stages were measured. For both zoeae stages, ETSA an d protein content remained constant after 27 h exposure to 160 ppb Hg where as RO2 and swimming activity decreased. This study revealed the impact of d ifferent Hg levels and different exposure times on RO2 of shrimp larvae. Af ter 10 h exposure to 160 ppb Hg, the RO2 decreased by 43 and 49% in zoeae I II and zoeae V stages, respectively. Exposure time of 27 h to 80 ppb Hg and higher, induced paralysis in nearly 100% larvae. Surprisingly, the paralys ed larvae displayed almost 50% of the control's RO2. The results showed tha t Hg disturbs a part of the respiration process without modifying the maxim um activity of the enzymes involved in the ETSA assay. Therefore, the ETSA assay can not be used as a sublethal bioanalytic probe to detect Hg in shor t-term exposures. The decline of the RO2/ETSA ratios reported here, indicat es an inability of contaminated larvae to adapt their metabolism to physiol ogical stress caused by Hg. (C) 1999 Elsevier Science Inc. All rights reser ved.