Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Counting Caenorhabditis elegans: Protocol Optimization and Applications for Population Growth and Toxicity Studies in Liquid Medium



Steven Lund, Sanem Hosbas Coskun, Monique Johnson, Christopher Sims, Elijah Petersen, John T. Elliott, Bryant C. Nelson, Leona D. Scanlan, Shannon K. Hanna, Karina Brignoni, Patricia Lapasett


The nematode Caenorhabditis elegans is used extensively in molecular, toxicological and genetics research. However, standardized methods for counting nematodes in liquid culture do not exist despite the wide use of nematodes and need for accurate measurements. Herein, we provide a simple and affordable counting protocol developed to maximize count accuracy and minimize variability in liquid nematode culture. Sources of variability in the counting process were identified and tested in 14 separate experiments. Three variables resulted in significant effects on nematode count: shaking of the culture, priming of pipette tips, and sampling location within a microcentrifuge tube. Between- operator variability did not have a statistically significant effect on counts, even among differently- skilled operators. The protocol was used to assess population growth rates of nematodes in two different but common liquid growth media: axenic modified Caenorhabditis elegans Habitation and Reproduction medium (mCeHR) and S-basal complete. In mCeHR, nematode populations doubled daily for 10 d. S-basal complete populations initially doubled every 12 h, but slowed within 7 d. We also detected a statistically significant difference between embryo-to-hatchling incubation period of 5 d in mCeHR compared to 4 d in S-basal complete. The developed counting method for Caenorhabditis elegans reduces variability and allows for rigorous and reliable experimentation.
Nature - Scientific Reports


whole organism metrology, Caenorhabditis elegans, counting, population growth rates, standardization


Lund, S. , Hosbas Coskun, S. , Johnson, M. , Sims, C. , Petersen, E. , Elliott, J. , Nelson, B. , Scanlan, L. , Hanna, S. , Brignoni, K. and Lapasett, P. (2018), Counting Caenorhabditis elegans: Protocol Optimization and Applications for Population Growth and Toxicity Studies in Liquid Medium, Nature - Scientific Reports, [online], (Accessed May 22, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 16, 2018, Updated October 12, 2021