Gravity plays an important role in most life forms on Earth. Yet, a complete molecular understanding of sensing and responding to gravity is lacking. While there are anatomical differences among animals, there is a remarkable conservation across phylogeny at the molecular level. Caenorhabditis elegans is suitable for gene discovery approaches that may help identify molecular mechanisms of gravity sensing. It is unknown whether C. elegans can sense the direction of gravity. In aqueous solutions, motile C. elegans nematodes align their swimming direction with the gravity vector direction while immobile worms do not. The worms orient downward regardless of whether they are suspended in a solution less dense (downward sedimentation) or denser (upward sedimentation) than themselves. Gravitaxis is minimally affected by the animals’ gait but requires sensory cilia and dopamine neurotransmission, as well as motility; it does not require genes that function in the body touch response. Gravitaxis is not mediated by passive forces such as non-uniform mass distribution or hydrodynamic effects. Rather, it is mediated by active neural processes that involve sensory cilia and dopamine. C. elegans provides a genetically tractable system to study molecular and neural mechanisms of gravity sensing.

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秀丽隐杆线虫表现出正向重力

重力在地球上的大多数生命形式中发挥着重要作用。然而，目前还缺乏对重力感应和响应的完整分子理解。虽然动物之间存在解剖学差异，但在分子水平上，整个系统发育存在显着的保守性。秀丽隐杆线虫适合基因发现方法，可能有助于识别重力感应的分子机制。目前尚不清楚秀丽隐杆线虫是否能够感知重力的方向。在水溶液中，能动的线虫将其游动方向与重力矢量方向对齐，而不动的蠕虫则不然。无论蠕虫悬浮在比自身密度低（向下沉降）还是密度更高（向上沉降）的溶液中，蠕虫都会向下定向。重力轴受动物步态的影响最小，但需要感觉纤毛和多巴胺神经传递以及运动性；它不需要在身体触摸反应中起作用的基因。重力不是由非均匀质量分布或流体动力学效应等被动力介导的。相反，它是由涉及感觉纤毛和多巴胺的活跃神经过程介导的。线虫提供了一个遗传上易于处理的系统来研究重力感应的分子和神经机制。