Nematode Body Mass and Metabolic Footprints

Rev 06/26/25

Explanation and Preamble

Body Mass of nematodes may be calculated using the Andrássy (1956) formula W = (L*D²)/(1.6*10⁶) where W is the mass (as fresh weight μg) per individual, L is the nematode length (μm) and D is the greatest body diameter (μm).

The formula is based on the generally elongate and cylindrical morphology of nematodes, tapering towards both ends with the anterior bluntly rounded and the posterior more acute.

Andrássy (1956) derived the formula by first calculating nematode volume (V) and then determining nematode density (S) as the specific gravity of liquids in which they neither rose nor sank.  Then, W = SV.

Nematode volume was determined initially as the sum of the volumes of a series of complete and truncated cones. Since the method was measurement-intensive, Andrássy sought proxies and determined that, for nematodes of different sizes, a formula for volume based on body diameter and length (V = (L*D²)/1.7, where1.7 is an empirically-determined constant, provided a volume estimate within 2% of that determined by the more intensive calculation.  Note, however, that Freckman (1982) reports deviations of 5-31% between  nematode volumes calculated by Andrássy's shortened formula and a computation-intensive approach using geometric shapes selected for each nematode morphotype.

I calculated volumes and body weights per Andrássy (1956) for 10,272 records of nematode species (males and females) based on data readily available in the literature.  Since ecosystem functions and services are often reported at the family or genus level, I determined average weight for the species (ased on females) in each family (204 families) or genus (987 genera).  Note that family assignments of nematode general differ among authorities, which may have considerable effect on the average weights and their standard deviations.  I provide family assignments for each species according to several authorities.

References

Andrássy I (1956) Die rauminhalst and gewichtsbestimmung der fadenwurmer (Nematoden). Acta Zoologica Academi Sciences, Hungary 2:l-15.

Freckman. D.W. (1982) Parameters of the nematode contribution to ecosystems. Pp 81-97 in Freckman, D.W. (ed) Nematodes in Soil Ecosystems. University of Texas Press, Austin.

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