Physiological determinants of individual variation in sensitivity to an organophosphate pesticide in Nile tilapia Oreochromis niloticus

Author(s)

McKenzie, David J. ; Blasco, Felipe R. ; Belao, Thiago C. ; Killen, Shaun S. ; Martins, Nathan D. ; Taylor, Edwin W. ; Tadeu Rantin, F.

• Document type: Journal article
• Source: AQUATIC TOXICOLOGY; v. 189, p. 108-114, AUG 2017.
• Web of Science Citations: 0

Abstract

Individual variation in sub-lethal sensitivity to the organophosphate pesticide trichlorfon was investigated in Nile tilapia, using critical swimming speed (U-crit) as an indicator. Tilapia exposed for 96 h to 500 mu g l-1 trichlorfon at 26 degrees C (Tcfn group, n = 27) showed a significant decline in mean U-crit, compared to their own control (pre-exposure) performance in clean water (-14.5 +/- 2.3%, mean +/- SEM), but also compared to a Sham group (n = 10) maintained for 96 h in clean water. Individuals varied in their relative sensitivity to the pesticide, with the decline in U-crit after exposure varying from 1 to 41%. The U-crit of the Tcfn group did not recover completely after 96 h in clean water, remaining 9.4 +/- 3.2% below their own control performance. The decline in performance was associated with a significant increase in net cost of aerobic swimming, of +28.4 +/- 6.5% at a sustained speed of 2 bodylengths s(-1), which translated into a significant decline in swimming efficiency (E-swim) of -17.6 +/- 4.0% at that speed. Within the T-cfn group, individual E-swim was a strong positive determinant of individual U-crit across all trials, and a strong negative determinant of individual% decline in U-crit after pesticide exposure (P < 0.001, linear mixed effect models). Trichlorfon had no effects on standard metabolic rate or active metabolic rate (AMR) but, nonetheless, individual U-crit in all trials, and% decline in U-crit after exposure, were strongly associated with individual AMR (positively and negatively, respectively, P < 0.001). Individual U-crit under control conditions was also a strong positive determinant of Ucrit after trichlorfon exposure (P < 0.001), but not of the% decline in U-crit performance. In conclusion, the OP pesticide impaired U-crit performance by reducing E-swim but individual tilapia varied widely in their relative sensitivity. Intrinsic individual physiology determined effects of the pesticide on performance and, in particular, good swimmers remained better swimmers after exposure. (AU)

• FAPESP's process: 15/22326-0 - The respiratory physiology of fishes: ecological and evolutionary significance of individual variation
• Grantee: Francisco Tadeu Rantin
• Support Opportunities: Research Grants - Visiting Researcher Grant - International