Ammonia toxicity tolerance and behavioural response in Zebrafish

The investigation was done to determine toxicity tolerance level of ammonia in zebrafish (Danio rerio) as the fresh water fish model and find out the indicative changes in behavioural patterns to identify ammoniacal toxicant induced stress. For this, adult age-matched zebrafish were exposed to 0.1 mg/L to 5 mg/L conc. of NH3 consecutively for 96 h. When measured under bioavailable NH3 fixed for the experimental groups, LC50 value was 0.89 mg NH3/l under repetitive exposure which was confirmed by Kaplan–Meier curve showing cumulative survival > 0.6 at 72 h but < 0.4 at 96 h for 1 mg/L NH3 repetitive exposure. Quantitative behavioural analysis showed increasing NH3 conc. and consecutive exposure decreased playing behaviour from ~ 60% to 30% for sub-acute toxicity and to 5% and less for acute toxicity of NH3, whereas increased stress movement from 15–20% to 25–35% for sub-acute and > 90% for acute toxicity. Other significant shifts of behaviour identified that playing, feeding, aggression and stress movements are the key indicative behaviours under ammoniacal stress. Continued contamination of unionized ammonia was found less tolerant to fish and acute to sub-acute levels were reflected though shift of specific behavioural attributes.