Effects of different concentrations of 2-phenoxyethanol on primary and secondary stress responses in Persian sturgeon, Acipenser persicus

Abstract

Summary The anaethetic effects of 2-phenoxyethanol (2-PE) on possible primary (cortisol level) and secondary (hematological indices and glucose level) stress responses were studied in Persian sturgeon (Acipenser persicus). Fish were first exposed to 0.1, 0.3, 0.5, 0.7, 0.9 and 1.1 ml L−1 2-PE, and the time to induction (deep anaethesia) and recovery were measured. At a concentration of 0.1 ml L−1, 2-PE failed to induce deep anaethesia in fish, whereas at concentrations of 0.7, 0.9 and 1.1 ml L−1 all fish were anaethetized within 3 min of exposure. For assessing possible stress effects caused by effective concentrations of 2-PE, the hematological indices, serum cortisol and glucose were determined in the deeply anaethetized fish as stress indicators. The 2-PE exposure resulted in significant increases in red blood cell (RBC) values at 0.3 and 0.5 ml L−1; parallel increases in hemoglobin values were also observed at these concentrations (P < 0.01). Moreover, a lower concentration of 2-PE (0.3 ml L−1) caused a significant increase in hematocrit values (P < 0.05). Among the hematological indices, mean corpuscular volume (MCV) values decreased at 0.5 ml L−1 when compared with the control and other groups (P < 0.05). Serum cortisol level was elevated at 0.3, 0.5 and 0.7 concentrations of 2-PE (P < 0.01). The glucose level followed a trend similar to that observed for cortisol. The outcome of these experiments shows that 2-PE at a concentration of 0.9 ml L−1 is a suitable anaesthetic for Persian sturgeon. This study demonstrates that rapid induction of deep anaethesia with a relatively high concentration of 2-PE (0.9 and 1.1 ml L−1) was associated with the lowest effects on signs of physiological stress in Persian sturgeon.