Machine for rapidly counting and measuring the size of small nematodes

Publisher Website
Google Scholar
Abstract
A machine has been developed to accurately count and size large populations of the small nematode Caenorhabditis elegans with minimal effort. Like the related Coulter counter, this machine detects the change in electrical current which a particle (nematode) produces as it passes between two electrodes in a small transducer. Despite the use of alternating current, detailed analysis shows that detection is based primarily on resistance changes. The machine also employs a sheathed‐flow system to orient the long thin animals reproducibly in the transducer, so that resistance changes correspond directly to animal size. Accurate, non‐destructive measurement of live nematodes which have a 20‐fold length‐to‐width ratio and vary over a 103 range in volume can be achieved at a counting rate of 103 per min with 1% coincidence. Sources of measurement errors have been identified and controlled or eliminated. The machine has been calibrated against the optically measured lengths of nematodes in all stages of the life cycle.
Keywords