An extended epiphenotype for an extended phenotype inToxoplasma gondiiinfected feral house mice

Abstract

Behavioural phenotypes are sometimes studied in the context of brain circuits and in correspondence to the underlying genotype of individual organisms. Thus, allelic variants of ion channels can alter memory performance by changing Ca +2 ion influx in neurons (Tang et al., 1999); or variants of oxytocin receptors can change bonding strength between sexual pairs (Young et al., 1999). The relationship between genotypes and behaviour is not always linear. For example, rats can be selectively bred to perform maze-running tasks. But the consequence of such artificial selection depends on the rearing environment of the selected lines (Cooper & Zubek, 1958). The 'maze-bright' and 'maze-dull' lines remain plainly different in the standard laboratory environment. At the same time, the difference vanishes if both groups are reared in an enriched sensory environment, demonstrating contingency and flexibility of the behaviour in the prevailing environment. Flexibility in these cases represents not a simple correspondence between genotype and behaviour but an environment-dependent conditionality in the form of an if-then-else algorithm. Epigenetic machinery provides another critical source of

Mechanisms and consequences of infection‐induced phenotypes

“…Pavey and Vyas (2023) provide a perspective in this special feature suggesting that parasite manipulation of hosts is an example of Richard Dawkins' extended phenotype concept (Dawkins, 2016) and may be accomplished through epigenetic changes in the host. Ngo et al (2023) presents empirical evidence supporting a parasite‐induced extended epiphenotype, as Toxoplasma gondii‐ infected, wild‐caught mice exhibit the same DNA hypomethylation as laboratory‐reared mice that were experimentally infected with T. gondii .…”

“…Work on a range of host taxa, including insects (Adamo, 2023), fish (Alves & Aubin‐Horth, 2023) and mammals (Ngo et al, 2023), suggests that infection‐induced phenotypes stem from immunological, neurophysiological, gene regulatory and other cellular‐level mechanisms (Adamo, 2013). Epigenetic changes in hosts likely drive much of the infection‐induced variation among individuals (Pavey & Vyas, 2023).…”

“…Recognition of the pivotal role that parasites play in the variability of animal phenotypes in nature is surprisingly low (Chretien et al, 2023). Several contributions to this special feature present practical guidance for researchers working in a range of disciplines to assess the role of infection in their study system, including behaviour (Salerno et al, 2023; Stockmaier et al, 2023; Tillman & Adelman, 2023; Vindas et al, 2023), performance (Chretien et al, 2023), physiology (Alves & Aubin‐Horth, 2023; Lopes, 2023; Seguel et al, 2023; Wu, 2023) and epigenetics (Ngo et al, 2023). Yet, there are still many unanswered questions.…”

“…Epigenetic changes in hosts likely drive much of the infection-induced variation among individuals (Pavey & Vyas, 2023). As one example of how epigenetic changes in the brain lead to increased behavioural variation within a population, male mice Mus musculus infected with T. gondii showed higher levels of hypomethylation of the arginine-vasopressin (AVP) promoter in the posterodorsal medial amygdala than uninfected controls (Ngo et al, 2023) 2023) reviews how behavioural mechanisms of parasite defence shift in animals that range along the sociality spectrum from solitary to colonial. For example, social insects (i.e.…”

“…This special feature highlights the various ways that parasites drive variation in host phenotypes. The contributed articles highlight diverse host–parasite systems across a broad range of taxa and include perspective and concept articles (Adamo, 2023; Lopes, 2023; Pavey & Vyas, 2023; Poulin et al, 2023; Stockmaier et al, 2023; Tillman & Adelman, 2023), a systematic literature review (Chretien et al, 2023), a meta‐analysis (Wu, 2023) and observational and experimental research conducted in laboratory and field settings (Alves & Aubin‐Horth, 2023; Ngo et al, 2023; Salerno et al, 2023; Seguel et al, 2023; Vindas et al, 2023; Will et al, 2023). In this Editorial, we contextualize each featured article's contribution to our understanding of how parasites generate intra‐ and interindividual differences in host phenotypes, how this trait variation reverberates across levels of biological organization from cells to communities and the role of the host's external environment in modulating these effects.…”