| Abstract: | Humic isolates have previously been shown to modulate the reproduction of the nematode, Caenorhabditis elegans Maupas . The aim of this study was to find out if a hormone‐like effect is an intrinsic feature of humic substances. Therefore, the same nematode bioassay was used with ten humic substances (XAD and/or reverse osmosis isolates). The results confirmed the hormone‐like effect of humic substances, nine isolates significantly increased the numbers of offspring per worm, one isolate did not modulate the reproduction of C. elegans. This effect occurred with XAD isolates and with reverse osmosis isolates as well. Thus, this effect is an intrinsic feature of humic substances. This reproduction modulating potential of humic substances may be due to alkylaromatics that are major structural and photo stable structural components, rather than to sterols that are only minor structural components. This is a new view about the direct interactions of humic with aquatic organisms. The effects haven been mathematically modeled by a simple approach, considering a hormone‐like effect (β) and a non‐hormone like effect, such as nutrient effect (α) on growth. The different effects observed can be interpreted in terms of trade‐offs between these two competing mode of actions. |
