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 odorants 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 17–20 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 odorants may influence early development of key olfactory processes. Our data could inform practices at conservation hatcheries that are used as part of enhancement programs for lake sturgeon.

环境因素在鱼类表型发育中发挥着至关重要的作用，这对于在自然线索存在的野外释放的养殖鱼类具有重要意义。研究兴趣集中于探讨早期接触饲料气味物质如何影响嗅觉发育。本研究旨在利用行为学、分子生物学和电生理学技术，评估将氨基酸L-丙氨酸引入养殖环境可能对淡水白鲟（Acipenser fulvescens）这一濒危物种的嗅觉感知、生长和存活发展产生何种影响。我们假设氨基酸的接触会影响从内源性到外源性摄食过渡期间的摄食行为发生，并预测在早期发育阶段引入L-丙氨酸将促进0龄淡水白鲟的生长和存活。此外，我们假设淡水白鲟的嗅觉是一种发育可塑的特性，预测在开始外源性摄食之前添加L-丙氨酸将影响与检测饲料线索相关的基因mRNA转录丰度。我们的方法是从受精后17-20天（DPF）开始，在开始外源性摄食之前每日添加L-丙氨酸。我们在17、21、26、31、50、65和80 DPF时对个体进行了采样。此外，通过电嗅觉图（EOG）在约1岁时测试了对L-丙氨酸的嗅觉敏感性。我们观察到L-丙氨酸处理组和对照组在死亡率或EOG反应上没有显著差异；然而，在发育过程中，形态学、行为以及所有基因的mRNA转录丰度上存在显著差异。我们的结果表明，嗅觉系统在L-丙氨酸处理下表现出直至50-65 DPF的发育可塑性，这表明环境气味物质可能影响关键嗅觉过程的早期发育。我们的数据可以为作为淡水白鲟增殖计划一部分的保护区养殖场实践提供信息。