Circadian metabolic rate and short-term response of juvenile green abalone (Haliotis fulgens Philippi) to three anesthetics

Abstract

Time-course experiments were performed on juvenile green abalone (Haliotis fulgens) to assess the degree of stress caused by the anesthetics magnesium sulfate (MS), benzocaine (BZ), and phenoxyethanol (PE). Metabolic rate (VO2) of abalone was reduced by 65, 35, and 18% during short-term (10 or 20 min) exposure to MS, BZ, and PE, respectively. Abalones significantly increased their VO2 above control values (1.5-fold) after removal of PE from metabolic chambers, whereas those treated with MS or BZ recovered their VO2 to preanesthesia values. Visual criteria of recovery generally coincided with those of metabolic measurements (i.e., 80% of abalone regained "normal" activity after 35 min postanesthesia), yet metabolic measurements showed that "fast" recovering abalone treated with PE maintained high VO2 values during 3-h postanesthesia. Abalone treated and nontreated with anesthetics exhibited a circadian metabolic rhythm, with 20-35% higher rates observed during dark than light hours. Despite the short-term metabolic alterations with MS, BZ, and PE, the present study suggests that all three anesthetics may be safely used in abalone. However, detailed evaluations are still needed to assess the effect of anesthesia on other physiological variables. The results obtained in this study highlight the importance of physiological evaluations when different chemical substances are used in aquatic invertebrates.