All experiments with zebrafish were performed using protocols approved by the University of Oregon Institutional Animal Care and Use Committee and following standard protocols23 . Zebrafish husbandry, veterinary care, and equipment used to generate zebrafish for this study were provided by Aquatic Animal Care Services at the University of Oregon, Eugene, OR. Experiments were conducted in the University of Oregon Zebrafish Facility or in the Guillemin laboratory. Embryonic and larval zebrafish were maintained in tissue culture flasks or petri dishes in Embryo Medium, a 4 parts per thousand salt solution made by mixing 5.25 grams Instant Ocean per 1 liter of dechlorinated water. Fish at post-larval stages were maintained in tanks in the University of Oregon Zebrafish Facility on system water. Facility system water quality parameter ranges are 650 to 950 microsiemens/cm2 (link) conductivity, 7.2 to 7.8 pH, 0 ppm ammonia, 0 ppm nitrites, 5 to 30 ppm nitrates, 30 to 100 ppm alkalinity. Water quality conductivity, pH, and temperature are continuously monitored by programmable logic controllers (PLCs) attached to aquaculture tank probes. Water quality tests for ammonia, nitrites, nitrates are performed using a colorimetric kit (Freshwater Master Test Kit, Aquarium Pharmaceuticals, Inc., Chalfont, PA). Alkalinity tests are performed using a freshwater alkalinity colorimeter (Model HI775 Freshwater Alkalinity Colorimeter, Hanna Instruments, Smithfield, RI). Water quality adjustments for conductivity and pH are made by PLC-controlled dosing pumps dispensing salt solution (Instant Ocean, Spectrum Brands, Blacksburg, VA) in the case of conductivity and basic solution (ProLine Sodium Bicarbonate, Pentair Aquatic Eco-Systems, Apopka, FL) in the case of pH. Water quality temperature is primarily provided by building HVAC room air handlers and supplemented by immersed heaters located in aquaculture tanks. Municipal water filtered through reverse osmosis membranes is pumped into aquaculture tanks to replace water lost from automatic particle filter washes, spills, and evaporation. WT (Ab/Tu) zebrafish were reared at 28°C. GF embryos were derived by surface sterilization of the chorions and maintained as previously described24 (link). Experiments were performed on larvae ranging from 4 dpf (~3.7 mm body length) to 8 dpf (~4.7 mm body length), as specified. No exogenous food was provided to the larvae during the duration of the experiments. CV controls were clutch mates of the GF derived embryos that were not subjected to surface sterilization and were reared in parallel.