A size threshold governs Caenorhabditis elegans developmental progression

The growth of organisms from humans to bacteria is affected by environmentalconditions. However, mechanisms governing growth and size control are not wellunderstood, particularly in the context of changes in food availability in developingmulticellular organisms. Here, we use a novel microfluidic platform to study theimpact of diet on the growth and development of the nematode Caenorhabditiselegans. This device allows us to observe individual worms throughoutlarval development, quantify their growth as well as pinpoint the moultingtransitions marking successive developmental stages. Under conditions of low foodavailability, worms grow very slowly, but do not moult until they have achieved athreshold size. The time spent in larval stages can be extended by over an order ofmagnitude, in agreement with a simple threshold size model. Thus, a critical wormsize appears to trigger developmental progression, and may contribute to prolongedlifespan under dietary restriction.