ABSTRACT
Rotifers, Brachionus plicatilis, are a valuable first exogenous feed for zebrafish because they can provide continuous nutrition for growing zebrafish larvae when used in a rotifer-zebrafish polyculture. Typically cultured at high salinities (>10 ppt), B. plicatilis are temporarily immobilized when moved to lower salinities (5 ppt) used for polycultures, decreasing their accessibility and attractiveness to the larvae. The nutritional value of rotifers varies based on their diet, typically live algae, which has limited nutritional value and may pose biosecurity risks. After confirming that rotifers consume and can reproduce when fed an irradiated, processed larval fish diet (PD), they were reared at 5 or 15 ppt, and fed various combinations of an algae mix and/or PD. Population densities and percentages of egg-bearing rotifers were quantified daily until the population density plateaued, and then their nutritional value was assessed. Results indicated that rotifers thrived at both salinities. Those fed PD were successfully maintained at >500 rotifers per mL and contained a greater ω-6/ω-3 fatty acid ratio. Our findings indicate that enriching rotifers with PD raised at 5 ppt can potentially eliminate rotifer immobilization in polyculture, while providing a nutritious, attractive diet for zebrafish larvae and decreasing biosecurity risks.
Subject(s)
Perciformes , Rotifera , Animals , Zebrafish , Salinity , Dietary Supplements , LarvaABSTRACT
Embryo surface disinfection in either an iodine or sodium hypochlorite (NaOCl) solution is commonly performed on imported zebrafish embryos to decrease pathogen introduction into a facility. The impact of the consecutive use of these disinfectants and the conductivity of the culture media on embryo survival and development post-disinfection have not been evaluated. Iodine (12.5-25 ppm) is effective at eliminating several Mycobacterium species, whereas NaOCl (50-100 ppm) reduces the number of viable Pseudoloma neurophilia spores. Casper and T5D (tropical 5D wild type) embryos reared in media of differing conductivities (0-10, 100-200, 750-950, and 1500-2000 µS) with and without exposure to NaOCl 100 ppm at 6 h post-fertilization were evaluated for survival, hatching success, and morphological defects at 5 days post-fertilization. Additionally, the consecutive use of iodine (12.5 ppm for 2 min) followed by NaOCl (75 or 100 ppm for 10 min), as well as the inverse, was evaluated. Embryo survival was not impacted by embryo rearing media alone; however, survival significantly decreased when embryos were disinfected with 100 ppm NaOCl in media with a conductivity >750-950 µS. Iodine (12 ppm) and NaOCl (75 ppm) used sequentially resulted in >50% survival, whereas the use of 100 ppm NaOCl resulted in high levels of embryo mortality.
