两栖动物从水生到陆生的过渡揭示了嗅觉的物理极限

中文摘要 AI 辅助

动物从水生到陆生的进化过渡需要感知和响应截然不同的环境。化学物质在水中的扩散速度比在空气中慢四个数量级，这要求嗅觉系统发生重大重塑。两栖动物是分析这些适应机制的有力模型，因为它们在单一生命周期中经历变态，从水生状态过渡到陆生状态。本研究利用实验室诱导的成年墨西哥钝口螈（Ambystoma mexicanum）变态，探究基本化学特性如何影响水生与陆生嗅觉。结合渐近理论与利用重建的嗅腔形态进行的数值模拟，研究发现气味在水中的吸附需要数十秒，而在空气中仅需毫秒级；短暂气味流的吸附在空气中吸气速度约为20厘米/秒时达到最大化，而在水中则接近零，这与观测到的水生墨西哥钝口螈可忽略的吸气量相匹配。尽管如此，水生墨西哥钝口螈能快速响应引入的气味分子：虽然水生与陆生墨西哥钝口螈嗅腔的形态差异几乎无关紧要，但水生嗅觉纤毛可泵送水以显著加快气味吸附速率；配合减少与目标 proximity 的适应性行为响应，等待时间可缩短至不到一秒。因此，尽管水生嗅觉比陆生嗅觉慢，但水生动物具备解剖学和行为学适应机制，支持化学检测作为一种近端感知。

英文摘要

The evolutionary transition from water to land required animals to sense chemicals under fundamentally different physical constraints. Because chemicals diffuse orders of magnitude more slowly in water than in air, aquatic olfaction faces significant challenges in odor capture. Yet, aquatic organisms exhibit strikingly sensitive and rapid chemosensory behaviors. Amphibians represent a powerful model to address this discrepancy because they transition from aquatic to terrestrial environments within a single lifetime. Here, we combine metamorphosis of adult axolotls with asymptotic theory and numerical simulations to show that odorants are captured by diffusion in tens of seconds in water compared with milliseconds in air; yet aquatic axolotls respond to odorants on a much more rapid timescale. Despite inefficiency, we find that proximity to large patches of highly concentrated odor supports sensation in the presence of flow. While aquatic axolotls did not display any respiratory flow, they display behavioral adaptations that generate flow and may even draw in odor through ciliary pumping. Thus, aquatic olfaction is slower and more wasteful than terrestrial olfaction, but behavioral adaptations support olfaction as an effective proximal sense.

发表机构

• University of Genoa（热那亚大学）
• Harvard University（哈佛大学）
• Gran Sasso Science Institute (GSSI)（格兰萨索科学研究所）

机构由 AI 辅助整理，请以论文原文为准。