Abstract:
The use of plant-derived essential oils in aquaculture has aroused interest due to their
bioactive properties, including anesthetic effects. This study investigated the chemical
composition and anesthetic effect of six plant-derived essential oils (EOs) (Eucalyptus
globulus - EGEO, E. citriodora - ECEO, Thymus vulgaris - TVEO, Mentha piperita - MPEO,
Melaleuca alternifolia - MAEO and Ocimum basilicum - OBEO) on juvenile Nile tilapia
(Oreochromis niloticus), a species of global economic importance. The chemical composition
of EOs was determined through high-resolution gas chromatography coupled with mass
spectrometry (GC/MS), and the anesthetic effect was assessed by the induction time to
anesthesia and recovery after exposing healthy tilapia (5±2 g) to 100 mg/L of EO or lidocaine
(positive control). The in vivo experiment with tilapia was performed in triplicate. Forty-five
compounds were identified. 1,8 cineole, ρ - cymene, citronellal, thymol, menthol, 1-terpinen-
4-ol and estragole were the major components of EGEO, ECEO, TVEO, MPEO, MAEO and
OBOE, respectively. All tested oils demonstrated anesthetic properties for juvenile Nile
tilapia. Lidocaine, EGEO and MAEO had similar anesthesia times (~30 min), TVEO
presented the shortest time (~4 min), followed by OBEO (~6 min). ECEO and MPEO had
intermediate times (~9 and ~23 min, respectively). Recovery time was very similar among
the experimental groups, except of the OEOB which had a longer time (p ≤ 0.003) and
mortality was observed. TVEO was the most effective anesthetic and can be recommended
for use in juvenile Nile tilapia. This study highlights the potential of using EOs as anesthetics
in aquaculture or aquaculture research.
