Maternal effects in nematodes: evidence, relevance & importance

Maternal effects are ubiquitous in free-living organisms, with parent-environment interactions affecting offspring life-history traits and fitness. These effects have been demonstrated in a wide variety of organisms, including mammals, insects and plants. Despite this, there is little evidence of maternal effects existing in parasites. If maternal effects are so prevalent in free-living organisms then it is unlikely that they do not exist in parasites. Maternal effects are important because they influence progeny fitness, measured by fecundity, longevity and developmental time. If they exist in parasite then they likely result in increased virulence, greater persistence (especially in terms of soil dwelling nematodes) and may be a driving influence in selection for resistance. Here, maternal effects are demonstrated in the free-living nematode Caenorhabditis elegans and the maternal effect of temperature demonstrated under constant and variable conditions. Similarly, the fitness effects of environmental temperature are explored in entomopathogenic nematodes and the effects of both maternal temperature and host species are demonstrated to cause changes in offspring development. Finally, C. elegans is used to demonstrate the importance of maternal effects in parasite life history and their potential impact on parasite control. The implications of altered life-history strategies that come about as a result of mothers tailoring their reproductive strategies in response to environmental cues for agricultural and medical parasite control are discussed. Critically, the effects of low parental exposure to anthelmintic compounds and nematicidal plant extracts on the fitness of offspring are demonstrated. This work provides evidence for the existence of maternal effects in freeliving and parasitic species and highlights the importance of the recognition of such effects in multiple fields.