Behavioural changes in slime moulds over time

Abstract

Changes in behaviour over the lifetime of single-cell organisms have primarily been investigated in response to environmental stressors. However, growing evidence suggests that unicellular organisms undergo behavioural changes throughout their lifetime independently of the external environment. Here we studied how behavioural performances across different tasks vary with age in the acellular slime mould Physarum polycephalum . We tested slime moulds aged from 1 week to 100 weeks. First, we showed that migration speed decreases with age in favourable and adverse environments. Second, we showed that decision making and learning abilities do not deteriorate with age. Third, we revealed that old slime moulds can recover temporarily their behavioural performances if they go throughout a dormant stage or if they fuse with a young congener. Last, we observed the response of slime mould facing a choice between cues released by clone mates of different age. We found that both old and young slime moulds are attracted preferentially toward cues left by young slime moulds. Although many studies have studied behaviour in unicellular organisms, few have taken the step of looking for changes in behaviour over the lifetime of individuals. This study extends our knowledge of the behavioural plasticity of single-celled organisms and establishes slime moulds as a promising model to investigate the effect of ageing on behaviour at the cellular level. This article is part of a discussion meeting issue ‘Collective behaviour through time’.

A multi-scale review of the dynamics of collective behaviour: from rapid responses to ontogeny and evolution

“…For example, Rolland et al . 's [ 179 ] study of ageing in the slime mould Physarum polycephalum could be extended further by investigating how developmental changes can be explained by the components contributing to decentralized decision making in these single-celled organisms. Siracusa et al .…”

“…These emergent properties suggest that developmental changes at the individual level may not correspond to changes at the collective level. For example, Rolland et al's [179] study of ageing in the slime mould Physarum polycephalum could be extended further by investigating how developmental changes can be explained by the components contributing to decentralized decision making in these single-celled organisms. Siracusa et al [180] examine how ageing in free-living rhesus macaques Macaca mulatta can impact individual-and group-level social properties.…”