Sharine Nunes Descovi

Essential oils (EOs) are increasingly studied as natural anesthetics for fish, offering potential alternatives to synthetic agents. This systematic review aimed to summarize the effects of EOs on Oreochromis niloticus, focusing on their efficacy in inducing sedation and anesthesia, recovery times, and associated physiological responses. A comprehensive search was conducted in the Scopus, Web of Science, and Wiley Online Library databases for studies published up to 10 December 2024. Studies evaluating EOs or their main components in O. niloticus with quantitative data on anesthesia or sedation were included. From 355 records initially identified, studies meeting the inclusion criteria were analyzed qualitatively. EOs rich in compounds such as linalool, carvacrol, and pulegone effectively induced anesthesia in less than 3 min, with recovery times under 10 min, aligning with operational standards for fish anesthesia. However, some EOs caused physiological changes that may be related to stress responses. Variability in experimental protocols and incomplete reporting of chemical composition limited the comparability between studies. EOs demonstrate promising anesthetic potential for O. niloticus, representing safe and environmentally sustainable alternatives. Further standardized and controlled studies are required to confirm their safety and optimize application in aquaculture.

This study evaluated the effects of dietary supplementation with citral on growth performance and intestinal parameters, and specific activity of the digestive enzymes of Sardinella brasiliensis. 240 juvenile S. brasiliensis were randomly distributed in a recirculating aquaculture system (RAS) composed of 12 circular tanks of 150 L (n = 20 per tank). A diet without citral addition (control) and three diets containing different levels of citral inclusion (0.5, 1.0 and 2.0 mL kg*feed–1) were used in the fish feeding management during 20 days. The indexes of zootechnical performance, survival, weight gain, specific growth rate, feed conversion and condition factor of the fish were verified, as well as digestive enzymes and histological analysis. A significant positive relationship was found between citral supplementation and fish survival. In the specific activity of digestive enzymes, dietary citral supplementation at 2.0 mL* kg feed–1 increased lipase and amylase activity. Citral supplementation positively influenced the number of villi and intestinal crypt depth. Furthermore, the inclusion of citral at 0.5 mL kg*feed–1 increased the intestine diameter of the fish. The results of the experiment suggest that the addition of citral as an additive in the diet of S. brasiliensis improved the survival of fish.

The objective of this study was to evaluate the possible relaxing effect of essential oils (EOs) (Aloysia triphylla and Lippia alba) and phytochemicals (citral and linalool) in the gastropod Pomacea canaliculata. Animals were exposed to compounds at the concentrations range of 25-750 µL L-1. Magnesium chloride (MgCl2, 10-50 g L-1) and control group (ethanol 6.75 mL L-1, highest concentration used for treatment dilution) were also tested. The EOs, citral and MgCl2 had no relaxing effect at the concentrations range tested, and citral caused aversive behavior (closure of the operculum) from 90 μL L-1. Exposure to linalool at 25, 50, 100, 200 and 400 µL L-1 relaxed 28, 76, 88, 96 and 100% of the animals, respectively. The concentrations of 25, 50 and 400 µL L-1 differed statistically from each other, while 100 and 200 µL L-1 were equal to 50 and 400 µL L-1. All animals recovered up to 40 min, except at of 400 µL L-1. Linalool is effective for relaxing P. canaliculata and can be useful in management techniques that require relaxation. However, further studies are needed to certify whether linalool is appropriate for maintaining animal welfare in invasive procedures that require total insensitivity.

This study aimed to evaluate the essential oil of Ocimum gratissimum L. (EOOG) for anesthesia and in the transport of Oreochromis niloticus. Experiment I determined the time of anesthesia induction and recovery during anesthesia of O. niloticus exposed to different concentrations of EOOG (0, 30, 90, 150, and 300 mg L⁻¹). Based on data from Experiment I, Experiment II evaluated the effect of 0, 30, and 90 mg L⁻¹ EOOG on blood parameters and oxidative stress immediately after anesthesia induction and 1 h after recovery. Experiment III evaluated the effect of 0, 5, and 10 mg L⁻¹ EOOG on blood variables immediately after 4.5 h of transport of juveniles. Concentrations between 90 and 150 mg L⁻¹ EOOG were efficient for anesthesia and recovery. The use of 90 mg L⁻¹ of EOOG prevented an increase in plasma glucose. Other changes in blood parameters and oxidative stress are discussed. The use of 10 mg L⁻¹ EOOG in transport increased plasma glucose and decreased hematocrit values immediately after transport. It is concluded that the use of 90 and 150 mg L⁻¹ EOOG causes anesthesia and recovery in O. niloticus within the time intervals considered ideal. The use of 90 mg L⁻¹ EOOG favored stable plasma glucose soon after anesthesia induction and 1 h after recovery, but caused changes in the antioxidant defense system by increasing hepatic and kidney ROS. The transport of 12 g O. niloticus for 4.5 h can be performed with concentration of 5 mg L⁻¹ of EOOG.