The prevalence of Caenorhabditis elegans across 1.5 years in selected North German locations: the importance of substrate type, abiotic parameters, and Caenorhabditis competitors

Abstract

Background: Although the nematode Caenorhabditis elegans is a major model organism in diverse biological areas and well studied under laboratory conditions, little is known about its ecology. Therefore, characterization of the species' natural habitats should provide a new perspective on its otherwise well-studied biology. The currently best characterized populations are in France, demonstrating that C. elegans prefers nutrient- and microorganism-rich substrates such as rotting fruits and decomposing plant matter. In order to extend these findings, we sampled C. elegans continuously across 1.5 years from rotting apples and compost heaps in three North German locations.

Results: C. elegans was found throughout summer and autumn in both years. It shares its habitat with the related nematode species C. remanei, which could thus represent an important competitor for a similar ecological niche. The two species were isolated from the same site, but rarely the same substrate sample. In fact, C. elegans was mainly found on compost and C. remanei on rotten apples, possibly suggesting niche separation. The occurrence of C. elegans itself was related to environmental humidity and rain, although the correlation was significant for only one sampling site each. Additional associations between nematode prevalence and abiotic parameters could not be established.

Conclusions: Taken together, our findings vary from the previous results for French C. elegans populations in that the considered German populations always coexisted with the congeneric species C. remanei (rather than C. briggsae as in France) and that C. elegans prevalence can associate with humidity and rain (rather than temperature, as suggested for French populations). Consideration of additional locations and time points is thus essential for full appreciation of the nematode's natural ecology.

Figure 1

Occurrence of C. elegans and C. remanei on compost and apple samples between July 2011 and December 2012 at different sampling sites. The months for which no rotten apples were available in the Münster farming museum are marked with a cross. In Kiel, rotten apple samples could be collected during the entire sampling period. For each substrate and location, at least six and usually more than ten independent samples were assessed for the presence of Caenorhabditis nematodes. More details are in given in Table 2, and Additional file 5: Table S1 and Additional file 6: Table S2.

Figure 2

Significant correlations between abiotic factors and proportion of samples containing C. elegans (dark grey bars) or C. remanei (light grey bars). Humidity (blue lines) correlates with the proportion of rotten apple C. remanei-containing samples in Kiel (A) and with the C. elegans-containing proportion of compost samples in Münster (C). Rain (green line) correlates with C. elegans prevalence in Kiel compost samples (B). The results of the correlation analysis are given in Tables 5 and 6.