Efficiency of thyme (Origanum onites) and coriander (Coriandrum sativum) essential oils on anesthesia and histopathology of rainbow trout (Oncorhynchus mykiss)

Highlights

• Anesthetic effects of thyme (Origanum onites) and coriander (Coriandrum sativum) essential oils on trout determined for the first time in this study.

• Coriander essential oil provided deep anesthesia at 200 mg L⁻¹ and deep sedation at 50 mg L⁻¹concentration in fish.

• No pathological findings were observed in any organ of fishes in coriander group.

• Thyme essential oil caused mortality in rainbow trout.

• Edema, inflammatory cell infiltrations and desquamation in gills and hyperemia in gill, liver and kidney of fish were observed in thyme group.

• The present study demonstrated that concentrations of 200 mg L⁻¹ coriander essential oil can be used for rainbow trout, but thyme essential oil is not suitable.

Abstract

The aim of this study was to investigate the anesthetic efficiency of coriander (Coriandrum sativum) and thyme (Origanum onites) essential oils at different concentrations (20, 50, 70, 100, 150, 200, 300, 400, 500, 600 mg L⁻¹) on rainbow trout (Oncorhynchus mykiss). Additionally, the histopathological effects of essential oils were investigated on the fish tissues including gill, liver and kidney. At the end of the experiment, coriander essential oil was observed to be sedative at 50 mg L⁻¹ and had an anesthetic effect at a concentration of 200 mg L⁻¹ in rainbow trout. However, thyme essential oil caused mortality at the tested concentrations in rainbow trout. Histopathological examination, hyperemia, edema and desquamation were observed in the thyme group’ gills. Also, liver and kidney hyperemia was noticed in this group. No pathological findings were observed in any organ of fishes in the coriander group. The present study demonstrated that concentrations of 200 mg L⁻¹ coriander essential oil can be used as an anesthetic for rainbow trout.

Introduction

Anesthetics are a widely used tool in calming, catching, transporting, sampling, surgery, measuring, fish handling procedures in aquaculture (Yanar and Genc, 2004; Hajek et al., 2006; Hoseini et al., 2021; Yousefi et al., 2022). The most commonly used anesthetics in aquaculture are MS222, quinaldine, benzocaine, methomidate, clove oil, eugenol and 2-phenoxyethanol (Zahl et al., 2009; Priborsky and Velisek, 2018). It has been reported that some synthetic anesthetics have significant side effects such as gill irritation, excessive mucus secretion, suppressing the cardiovascular system, respiratory function and immune system of fish (Gilderhus and Marking, 1987; Palić et al., 2006; Roohi and Imanpoor, 2015; Aydın and Barbas, 2020). Herbal essential oils are an excellent alternative for synthetic products. Therefore, they have been widely tested as anesthetics for fish in recent years (Hajek, 2011; Ribeiro et al., 2016; Silva et al., 2019; Aydin and Orhan, 2021).

The coriander belonging to the Umbelliferae / Apiaceae family is widely produced all over the world for its fruit and essential oil (Msaada et al., 2009; Ghobadi and Ghobadi, 2012; Mandal and Mandal, 2015). Coriander plants are used as a sedative and pain reliever and the main component of coriander essential oil is linalool (Sugawara et al., 1998; Gastón et al., 2016; Satyal and Setzer, 2020). There is one study on the use of coriander essential oil as anesthetic in fish. Can et al. (2019) informed that coriander essential oil has anesthetic effects for convict cichlid (Amatitlania nigrofasciata). In the present study, the anesthetic effects of coriander essential oil in trout were studied for the first time.

Thyme, belonging to the Lamiaceae family, is an important aromatic plant and used for medicinal and spice purposes almost all over the world. The major components of thyme essential oil include thymol and carvacrol. The anesthetic and sedative effects of thyme essential oil in fish have been reported in zebrafish (Seyidoglu and Yagcılar, 2020), sea bass (Dicentrarchus labrax) and meagre (Argyrosomus regius) (Bodur et al., 2018).

In recent studies, it has gained importance in determining the histopathological effects of essential oils used as anesthetics on fish (Veliseck et al., 2005; Bhuvaneswari et al., 2015; Brandão et al., 2021). In anesthetic studies particularly the most affected organs are gills. Histopathological studies are critical to verify the sensitivity of the organs to toxic substances, mainly the gill epithelium (Poleksic and Mitrovic-Tutundzic, 1994). Balamurugan et al. (2016) reported that clove oil exposure can cause the accumulation of extract on gill tissues in clownfish. Jia et al. (2022) informed that gill histological changes were observed after fish (Oplegnathus punctatus) exposure to clove oil. As far as we know, there is no histopathological study on the use of thyme and coriander essential oil as an anesthetic in fish.

In this study, anesthetic and histopathological effects (gill, liver and kidney) were investigated in rainbow trout exposed to different concentrations of thyme (Origanum onites) and coriander (Coriandrum sativum) essential oils.