Adult influence on juvenile phenotypes by stage-specific pheromone production

Abstract

1Animals and plants can predict decreasing food supplies by recognition of population density, 2 and respond by adjusting behavioral and morphological traits. Population density in nematodes 3 is detected through pheromones, influencing dormant (dauer) stage entry, and in some lineages 4 alternative mouth-form decision (bacterivorous vs. predatory). Whether age is a relevant 5 parameter in recognizing population density is not well understood. Here, we utilized the mouth-6 form plasticity of the model nematode Pristionchus pacificus and developmental pheromone 7 profiling to study potential parent:progeny communication. Surprisingly, we observed adult-8 specific production of molecules that induce the predatory morph, even though adult mouth 9 forms are no longer plastic. We introduce a novel dye-based method to differentiate populations 10 in mixed-generation cultures, and found adults, but not peers, influence developing juvenile 11 mouth forms. Finally, we applied a logistic growth model that demonstrates adults both lower 12 the population carrying capacity and decrease the time until resource depletion. In the 13 necromenic life cycle of P. pacificus, we view mouth-form plasticity as an alternative 'Malthusian 14 escape' strategy to dauer that responds to age-specific population densities. The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/291591 doi: bioRxiv preprint first posted online Mar. 29, 2018; Population density is an important ecological parameter that correlates with increased 26 competition for resources 1 . In addition to density-dependent selection 2 , which operates on 27 evolutionary time scales, some organisms can respond dynamically to population density by 28 phenotypic plasticity. For example, plants can sense crowding by detecting the ratio of red 29 (chlorophyll absorbing) to far red (non-absorbing) light, and respond by various shade-30 avoidance strategies including higher shoots 3 . Locusts undergo solitary to swarm (i.e. 31 gregarious) transition, and aphids can develop wings, both as a result of increased physical 32 mechanosensory contact [4][5][6] . Intriguingly, population density can also have transgenerational 33 effects. For example, adult crowding of the desert locust Schistocerca gregaria 7,8 and migratory 34 locust Locusta migratoria 9 also influences the egg size, number, and morphology of their 35 progeny, and high population densities of red squirrels elicit hormonal regulation in mothers to 36 influence faster developing offspring 10 . Nevertheless, while incorporating age into population 37 structures has significantly advanced density-dependent selection theory 11 , surprisingly little 38age-specific refinement has been incorporated into models of phenotypic plasticity, especially at 39 the mechanistic level. This is partly due to the competing challenges of (1) studying population 40 ecology in the laboratory, and (2) the paucity of laboratory model organisms that are suitable for 41 ecological studies. The model nematode ...

Neuronal perception of the social environment generates an inherited memory that controls the development and generation time of C. elegans

“…The composition of whole pheromone in this species is stage specific, such that only pheromone produced by adults, not juveniles, can elicit an alternative developmental trajectory, a predation-enabling mouth morphology, in developing worms. 66 In contrast, our study demonstrates direct inheritance of parental pheromone perception to alter progeny phenotypes, similar to recent reports, 67 including one in another nematode species. 68 Given the importance of conspecific competition to organisms of all kinds, we speculate that such mechanisms to alter progeny phenotypes in response to the size and state of the population are widespread.…”

Nematode biphasic ‘boom and bust’ dynamics are dependent on host bacterial load while linking dauer and mouth‐form polyphenisms

“…1C), that in addition to bacterial feeding, allows for predation on both fungi and other nematodes (Susoy and Sommer, 2016; Sudhaus 2010; Ragsdale et al ., 2013). Like dauer, mouth form is also influenced by population density and environmental conditions, including food availability and age‐class‐dependent crowding effects (Sanghvi et al ., 2016; Werner et al ., 2017; Werner et al ., 2018). Thus, the decomposing beetle carcass teeming with assorted bacteria and nematodes is an ideal system to study the intricacies of multivariate symbioses and their effects on plasticity and niche construction.…”

Neuronal perception of the social environment intergenerationally controls germline development and generation time inC. elegans

“…Previous work in the nematode Pristionchus pacificus has shown that pheromone can indicate the age structure of a burgeoning population to adaptively influence progeny developmental outcomes. The composition of whole pheromone in this species is stage-specific, such that only pheromone produced by adults, not juveniles, can elicit an alternative developmental trajectory, a predationenabling mouth morphology, in developing worms (Werner et al 2018). In contrast, our study demonstrates direct inheritance of parental pheromone perception to alter progeny phenotypes.…”