Abstract
RESUMO:The effects of anesthesia with the essential oil of Ocimum gratissimum (EOO) in parameters of stress after handling were investigated in silver catfish (Rhamdia quelen). EOO was obtained from the aerial parts by hydrodistillation. Juveniles were anesthetized with 70 or 300 mg L-1 EOO and submitted to air exposure for 1 minute. The fishes were sampled immediately or transferred to anesthetic-free aquaria until sampling. In the first experiment, juveniles had their blood collected at 0, 1, 4, and 8 h after handling to assay plasma cortisol and blood glucose levels. The unanesthetized animals were restrained manually for blood collection. In the second experiment, water samples of the recovery aquaria were collected to evaluate net ion fluxes at 0 - 4 h and 4 - 8 h. Water and ethanol controls were also performed under the same conditions. The results showed that the cortisol levels did not differ among the treatments. Hyperglycemia was verified in fish exposed to 70 and 300 mg L-1 EOO at 1 h and 4 h after handling. After 8 h, cortisol and glucose concentrations were lower or similar than those from immediately after handling for all treatments. EOO anesthesia prevented Na+ efflux observed in the control groups in both flux periods. There were net Cl- and K+ effluxes at 0 - 4 h and influxes at 4 - 8 h after handling in most treatments, and these fluxes did not differ among the treatments. The results suggest that EOO did not impair stress recovery and did not act as an additional handling stressor in silver catfish.
Highlights
Anesthetics are often used to reduce fish movement and stress during fish farming procedures (Kiessling et al, 2009)
For silver catfish (Rhamdia quelen), the fish species used in this study, anesthesia with eugenol and the essential oil of Lippia alba prevented plasma cortisol increase in fish submitted to air exposure (Cunha et al, 2010a, b)
The different induction times to anesthesia observed in both studies may have been influenced by biological factors such as age, sex, life stage, body weight, and physiological condition, as well as environmental factors such as water temperature, pH, and dissolved oxygen level (Zahl et al, 2012)
Summary
Anesthetics are often used to reduce fish movement and stress during fish farming procedures (Kiessling et al, 2009). Stress response corresponds to an animal’s attempt to maintain its homeostatic state (Barton, 2002; Kiessling et al, 2009) It involves the activation of neuroendocrine pathways, which promote catecholamine and corticosteroid (cortisol) release. For silver catfish (Rhamdia quelen), the fish species used in this study, anesthesia with eugenol and the essential oil of Lippia alba prevented plasma cortisol increase in fish submitted to air exposure (Cunha et al, 2010a, b). This nocturnal species is one of the most widespread inhabitants of South American rivers, and has been considered a good alternative to fish production, as a result of its fast growth rate (Barcellos et al, 2001; Koakoski et al, 2012). It is susceptible to stress resulting from confinement and handling procedures, such as capture, tank transference, and air exposure (Barcellos et al, 2001, 2006; Cunha et al, 2010a, b)
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