Circular Estimate Method (CEM) - a Simple Method to Estimate Caenorhabditis elegansCulture Densities in Liquid Medium

Marcelo Estrella JosendeEmail author View ORCID ID profile,
Silvana Manske Nunes,
Larissa Müller,
Marlize Ferreira-Cravo,
José Marìa Monserrat and
Juliane Ventura-Lima

Biological Procedures Online201921:1

https://doi.org/10.1186/s12575-018-0089-2

Received: 24 September 2018
Accepted: 28 December 2018
Published: 15 January 2019

Abstract

Background

Nematodes are used in many different fields of science, including environmental and biomedical research. Counting and/or estimating nematode numbers is required during research. Although being one of the most common procedures, this apparently simple task is a time-consuming process, prone to errors and concerns regarding procedure, reliability, and accuracy. When an estimate is necessary, there is a traditional manual counting procedure that in this study it will be called as “drop method” (DM). This popular method that extrapolates an animal count from a small drop of fluid shows a high coefficient of variation. To solve this problem, the present study used the free-living nematode Caenorhabditis elegans to develop a new estimation procedure that was based on a relationship between area and volume of a larger sample.

Results

The new method showed a low coefficient of variation and a close relationship between estimated and real counts of the total number of nematodes in large C. elegans suspensions. Reactive oxygen concentration was measured as an example of method application and to allow comparison between methods.

Conclusion

The proposed method is accurate, facile and reproducible, requiring simple, inexpensive materials that make it an excellent alternative to the DM manual counting procedure. Although the DM is faster, its estimates are not as accurate or as precise as those of the new proposed method.