對線蟲（Caenorhabditis elegans）檢測氧濃度的方式所做的一項(xiàng)研究顯示,，在氧濃度檢測與線蟲進(jìn)食之間有一個(gè)驚人的聯(lián)系,。線蟲生活在土壤中，其中的氧壓變化很大,，所以它們會對氧濃度的很小變化做出反應(yīng)。線蟲喜歡生活在氧氣含量2-12% 的大氣中（空氣中氧氣的體積比為21%）。線蟲對低氧壓的規(guī)避是眾所周知的,，但關(guān)于其對氧的耐受性的一個(gè)上限的發(fā)現(xiàn)卻是一個(gè)新發(fā)現(xiàn)。研究表明,，線蟲對氧的檢測依賴于GCY-35,，這是一種含有血紅素的鳥苷酸環(huán)化酶,，也是由氧調(diào)節(jié)的。當(dāng)線蟲表現(xiàn)出一種被稱為“社會進(jìn)食”的刻板行為時(shí),，這種雙重功能就會發(fā)揮作用,。所謂 “社會進(jìn)食”，是指當(dāng)氧濃度超過一定量時(shí),，線蟲聚集在一起在有細(xì)菌的草地上進(jìn)食,。為什么高氧濃度會誘發(fā)這種行為？答案看來似乎是,，這些有細(xì)菌的草地消耗氧的速度快于氧通過草地?cái)U(kuò)散的速度,，從而將氧濃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.
