Effect of L-alanine exposure during early life stage on olfactory development, growth and survival in age-0 lake sturgeon Acipenser fulvescens.

Environmental factors play an important role in phenotypic development of fishes, which has implications for hatchery-reared fishes that are released into the wild where natural cues are present. There is interest in examining how early exposure to dietary odourants can affect development of olfaction. The aim of our study was to use behavioural, molecular and electro-physiological techniques to evaluate how introduction of the amino acid L-alanine to the rearing environment might influence the development of olfactory perception of dietary cues, growth and survival in lake sturgeon (Acipenser fulvescens), a species of conservation concern. We hypothesized that exposure to amino acids would influence the onset of feeding during dietary transitions from endogenous to exogenous feeding and predicted that the introduction of L-alanine during early development would promote growth and survival of age-0 lake sturgeon. Additionally, we hypothesized that olfaction in lake sturgeon is a developmentally plastic trait, predicting that the addition of L-alanine prior to exogenous feeding would influence mRNA transcript abundance of genes associated with detection of dietary cues. Our approach was to add L-alanine daily from 17 to 20 days post-fertilization (DPF) before the onset of exogenous feeding. We sampled individuals at 17, 21, 26, 31, 50, 65 and 80 DPF. Additionally, olfactory sensitivity to L-alanine was tested at ~1 year via electro-olfactogram (EOG). We observed no significant differences in mortality or EOG response between L-alanine and control treatments; however, significant differences were observed in morphometrics, behaviour and mRNA transcript abundance of all genes throughout development. Our results indicated the olfactory system exhibited developmental plasticity in response to L-alanine treatment until 50-65 DPF, suggesting that environmental odourants may influence early development of key olfactory processes. Our data could inform practises at conservation hatcheries that are used as part of enhancement programmes for lake sturgeon.