Effective concentration of herbal anaesthetics Origanum vulgare L. oil and its effects on stress parameters in Nile tilapia (Oreochromis niloticus).

BACKGROUND: Using anaesthetics is an important application in aquaculture especially where the fish transportation, vaccination, grading, sorting activities and many other handling operations have been conducted during the different stages of production periods in the farms or hatcheries. OBJECTIVES: This study aimed to evaluate the efficacy of oregano essential oil (OO) as an anaesthetic for Nile tilapia and to determine the optimal concentration and post-application stress effects compared to clove oil (CO). METHODS: Nile tilapia juveniles were exposed to different concentrations of OO (20-40-60-80-100 mg L-1) and CO (50 mg L-1) for different time periods to determine the optimal concentration and exposure time. After the effective concentration of OO was determined, in the second experiment, stress parameters (glucose, plasma cortisol) were analysed after 0, 2, 6, 12 and 24 h of application. The results compared to the control group and CO results. RESULTS: The study found that OO which has carvacrol compound higher than 78% was an efficient anaesthetic for Nile tilapia, and the effective concentration was found to be 60 mg L-1. No significant differences were found between opercular beats in any concentration of OO and CO. Basal glucose level in blood without anaesthesia application and recorded at 39.33 mg dL-1 and significantly lower than OO and CO at first two sampling points, 0 and 2 h (p < 0.05). According to plasma cortisol level results, although CO experimental group showed secondary stress response at 12 h (17.91 ± 4.21 ng mL-1), OO and CO group cortisol levels decreased at 24 h after anaesthesia application 7.13 ± 0.14and 7.01 ± 0.54 ng mL-1, respectively, below the control group cortisol concentration (12.28 ± 1.81 ng mL-1). CONCLUSIONS: These findings have important implications for the aquaculture industry as the use of OO as an anaesthetic could reduce the stress and mortality associated with traditional anaesthetics. Further research is needed to evaluate the efficacy of OO as an anaesthetic agent for other fish species and to determine the optimal concentration and exposure time for different species.

A novel technique for mass induction of propagation in small fish species: Hormone immersion.

Due to the lack of environmental stimuli found in their natural habitat, not all species of tiny fish can reproduce naturally in the conditions of captivity. Silver rasbora (Rasbora argyrotaenia) was used as the model organism in this study, which is the first to successfully use the hormonal technique of immersion to mass induce spawning and spermiation in small fish species. In this study, in order to find out the effect of immersion hormone treatment, two separate experiments in which commercial hormone Ovaprim™ was used for spawning induction and Ovagold™ for spermiation induction were conducted. Four doses of hormones (0.0 mL/L, 0.7 mL/L, 1.4 mL/L, and 2.1 mL/L) were evaluated on 24 females and 40 males in total. According to the experimental findings of female breeders, 1.4 mL/L dose of Ovaprim™ showed best results on latency period (8.67 h) with a total number of eggs (6994 egg) and fertilization rate (99.22 %). In addition, hatching and larval survival rate have also increased. Milt volume and sperm concentration have also seen an increase to 4.25 µL/g bw and 42.71 106 cell/µL respectively at 2.1 mL/L hormone concentration. The best results or responses were obtained by immersion treatments using Ovaprim™ doses of 1.4 mL/L on female and Ovagold™ concentrations of 2.1 mL/L on male. This new technique is a beneficial for breeding small fish species for either commercial or conservational culture condition.

Induction of spermiation using Ovaprim™ with topical gill method in the silver rasbora (Rasbora argyrotaenia).

The main obstacles on silver rasbora (Rasbora argyrotaenia) culture are having the limited number of broodstock and spawning depending on the season. The purpose of this study was to determine the effect of different dosage of Ovaprim™ induction by topical gill method to silver rasbora spermiation in order to continue the production out of its reproduction season with an optimum dose. A total of 30 male fish with a weight of 7.78 ±â€¯0.20 g and length 4.11 ±â€¯0.31 cm was used in this research. Topical gill treatments of Ovaprim™ were administered with following doses; 0.15 µl/g, 0.25 µl/g, 0.35 µl/g, 0.45 µl/g and 0.55 µl/g body weight. Milt volume, sperm concentration, sperm motility, and sperm viability parameters were observed in this study to understand the optimum dose of Ovaprim™ for male silver rasbora breeders. Spermiation induction of silver rasbora using Ovaprim™ with topical gill method has been successfully carried out, indicating an increase (P < 0.05) in milt volume, sperm concentration, sperm motility, and sperm viability. According to results a dose of Ovaprim™ is recommended to be used the 0.25 µl/g body weight in the spermiation induction of silver rasbora.

Description of embryonic development of spotted green pufferfish (Tetraodon nigroviridis).

Pufferfish species of the Tetraodontidae family carry the smallest genomes among vertebrates. Their compressed genomes are thought to be enriched for functional DNA compared to larger vertebrate genomes, and they are important models for comparative genomics. The significance of pufferfish as model organisms in comparative genomics is due to the availability of two sequenced genomes, that of spotted green pufferfish (Tetraodon nigroviridis) and fugu (Takifugu rubripes). However, there is only a very limited utilization of pufferfish as an experimental model organism, due to the lack of established husbandry and developmental genetics protocols. In this study, we provide the first description of the normal embryonic development of Tetraodon nigroviridis. Embryos were obtained by in vitro fertilization of eggs, and subsequent development was monitored by brightfield microscopy at constant temperature. Tetraodon development was divided into distinct stages based on diagnostic morphological features, which were adopted from published literature on normal development of other fish species like medaka (Oryzias latipes), zebrafish (Danio rerio), and fugu. Tetraodon embryos show more similar morphologies to medaka than to zebrafish, reflecting its phylogenetic position. The early developmental stage series described in this study forms the foundation for the utilization of tetraodon as an experimental model organism for comparative developmental studies.