对线虫（Caenorhabditis elegans）检测氧浓度的方式所做的一项研究显示，在氧浓度检测与线虫进食之间有一个惊人的联系。线虫生活在土壤中，其中的氧压变化很大，所以它们会对氧浓度的很小变化做出反应。线虫喜欢生活在氧气含量2-12% 的大气中（空气中氧气的体积比为21%）。线虫对低氧压的规避是众所周知的，但关于其对氧的耐受性的一个上限的发现却是一个新发现。研究表明，线虫对氧的检测依赖于GCY-35，这是一种含有血红素的鸟苷酸环化酶，也是由氧调节的。当线虫表现出一种被称为“社会进食”的刻板行为时，这种双重功能就会发挥作用。所谓 “社会进食”，是指当氧浓度超过一定量时，线虫聚集在一起在有细菌的草地上进食。为什么高氧浓度会诱发这种行为？答案看来似乎是，这些有细菌的草地消耗氧的速度快于氧通过草地扩散的速度，从而将氧浓度降到更舒服的水平。
Nature \ 430, 317 - 322 (15 July 2004); doi:10.1038/nature02714
Oxygen sensation and social feeding mediated by a C. elegans guanylate cyclase homologue
Specialized oxygen-sensing cells in the nervous system generate rapid behavioural responses to oxygen. We show here that the nematode Caenorhabditis elegans exhibits a strong behavioural preference for 5–12% oxygen, avoiding higher and lower oxygen levels. 3',5'-cyclic guanosine monophosphate (cGMP) is a common second messenger in sensory transduction and is implicated in oxygen sensation. Avoidance of high oxygen levels by C. elegans requires the sensory cGMP-gated channel tax-2/tax-4 and a specific soluble guanylate cyclase homologue, gcy-35. The GCY-35 haem domain binds molecular oxygen, unlike the haem domains of classical nitric-oxide-regulated guanylate cyclases. GCY-35 and TAX-4 mediate oxygen sensation in four sensory neurons that control a naturally polymorphic social feeding behaviour in C. elegans. Social feeding and related behaviours occur only when oxygen exceeds C. elegans' preferred level, and require gcy-35 activity. Our results suggest that GCY-35 is regulated by molecular oxygen, and that social feeding can be a behavioural strategy for responding to hyperoxic environments.
gcy-35::gfp is expressed in URX, AQR, PQR and other sensory neurons. a, Lateral view of the anterior body showing URX, AQR, SDQR and BDU neurons. Anterior is at left and ventral is down. b, Ventral view of the tail showing PQR and ALNL/R neurons. The more posterior cells may be PLM neurons, the sisters of ALNL or ALNR, or PLN neurons.
