Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N4N1, Canada.
Neurobiol Learn Mem. 2011 May;95(4):393-403. doi: 10.1016/j.nlm.2010.11.017. Epub 2010 Dec 2.
The freshwater snail Lymnaea stagnalis (L.) is considered a calciphile and exhibits reduced growth and survival in environments containing less than 20 mg/l environmental calcium. Although it has no apparent effect on survival at 20 mg/l, reducing environmental calcium increases metabolic demand, and as such we consider that this level of calcium acts as a stressor on the snail. We exposed snails to acute periods of low environmental calcium and tested their ability to form intermediate-term memory (ITM) and long-term memory (LTM) following one trial operant conditioning (1TT) to reduce aerial respiratory activity in hypoxic conditions. We also assessed whether there were changes in the electrophysiological properties of a single neuron, right pedal dorsal 1 (RPeD1), which has been demonstrated to be necessary for LTM formation. Following training in high (80 mg/l) environmental calcium, L. stagnalis formed ITM and LTM lasting 24 h and demonstrated a significant reduction in all activity measured from RPeD1; however when snails were exposed to low (20 mg/l) environmental calcium they were able to form ITM but not LTM. Although no behavioral LTM was formed, a partial reduction in RPeD1 activtiy measured 24 h after training was observed, indicating a residual effect of training. The strong effect that environmental calcium concentration had on physiology and behavior in response to training to reduce aerial respiration in L. stagnalis suggests that it is an element of gastropod husbandry that needs to be carefully considered when studying other traits. This study also indicates that L. stagnalis found naturally in low calcium environments may be less able to adapt to novel stressors than populations found in harder waters.
淡水蜗牛 Lymnaea stagnalis（L.）被认为是一种嗜钙生物，在环境中钙含量低于 20 毫克/升的情况下，其生长和存活能力会降低。尽管在 20 毫克/升的环境中，它对存活没有明显影响，但降低环境中的钙会增加代谢需求，因此我们认为这种水平的钙对蜗牛是一种应激源。我们让蜗牛经历了一段时间的低环境钙暴露，并测试了它们在一次操作性条件反射试验（1TT）后形成短期记忆（ITM）和长期记忆（LTM）的能力，以减少在低氧条件下的空中呼吸活动。我们还评估了单个神经元——右脚背侧 1 神经元（RPeD1）的电生理特性是否发生了变化，该神经元已被证明对 LTM 的形成是必要的。在高（80 毫克/升）环境钙下进行训练后，L. stagnalis 形成了持续 24 小时的 ITM 和 LTM，并显示出 RPeD1 所有活动的显著减少；然而，当蜗牛暴露在低（20 毫克/升）环境钙下时，它们能够形成 ITM，但不能形成 LTM。虽然没有形成行为性 LTM，但在训练后 24 小时测量到 RPeD1 活性的部分减少，表明训练有残余效应。环境钙浓度对生理和行为的强烈影响，以及对减少 L. stagnalis 空中呼吸的训练反应，表明它是腹足类动物饲养的一个要素，在研究其他特征时需要仔细考虑。这项研究还表明，在低钙环境中自然发现的 L. stagnalis 可能比在硬水中发现的种群更难适应新的应激源。
