Adaptive motility and feeding strategies of deep-branching predatory protists
Abstract
Heterotrophic flagellates play a major role in nutrient recycling and shaping aquatic microbial communities. Many motile species have evolved diverse predatory strategies to exploit microbial prey, from bacteria to small eukaryotes. Excavates, deep-branching eukaryotic lineages with distinctive biflagellate morphology and conserved cytoskeletal features, exhibit varied feeding behaviours, including grazing, raptorial feeding, and filter-feeding. However, the temporal dynamics of their motility, feeding, and spatial distribution in relation to bacterial population density remain under-explored. Here, we quantify the behavioural ecology of excavates using high-resolution, single-cell tracking and quantitative analysis. Focussing on two Discoba species – the marine Jakoba libera and freshwater Reclinomonas americana – we identify different behavioural patterns: J. libera swims, forages and feeds, while R. americana swims and feeds. Prey availability differentially affects motility: J. libera increases the number of swimming cells when food is scarce, while R. americana shows the opposite trend. Spatial statistics reveal fundamental differences in their feeding and redistribution strategies. J. libera acts as an active forager, whereas R. americana behaves as a strict filter feeder. A third species, the anaerobic Kipferlia bialata (from a different clade), adopts a foraging strategy similar to J. libera . Together, these results elucidate the adaptive relationship between prey availability, feeding modes, and motility in bacteriovorous excavate flagellates, offering new insights into the ecological and evolutionary dynamics of microbial predators. SIGNIFICANCE Microbial hunters and predators that feed on other small organisms play an important role in aquatic food webs. Many species are motile, with seemingly adaptive behaviours that are difficult to quantify. Here, we focus on different species of early-diverging biflagellates that share a common morphology consisting of two flagella and a feeding groove, which it uses to feed on surface-associated bacterial prey. We demonstrate how the predator’s behavioural profiles shift as prey abundance changes over many days of a culture cycle, accompanied by evolving patterns of spatial distribution. Species-specific differences provide insights into the mechanisms of environmental adaptation in early eukaryotes.
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BibTeX
@misc{bouvard2026adaptive,
title = {{Adaptive motility and feeding strategies of deep-branching predatory protists}},
author = {Julien Bouvard and Angéline Girard and Samuel A Bentley and Harold Auradou and Kirsty Y Wan},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.64898/2026.10.08.757618},
url = {https://hal.science/hal-05801087v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Adaptive motility and feeding strategies of deep-branching predatory protists
AU - Julien Bouvard
AU - Angéline Girard
AU - Samuel A Bentley
AU - Harold Auradou
AU - Kirsty Y Wan
PY - 2026
DA - 2026/10/07
PB - HAL
DO - 10.64898/2026.10.08.757618
UR - https://hal.science/hal-05801087v1
AB - Heterotrophic flagellates play a major role in nutrient recycling and shaping aquatic microbial communities. Many motile species have evolved diverse predatory strategies to exploit microbial prey, from bacteria to small eukaryotes. Excavates, deep-branching eukaryotic lineages with distinctive biflagellate morphology and conserved cytoskeletal features, exhibit varied feeding behaviours, including grazing, raptorial feeding, and filter-feeding. However, the temporal dynamics of their motility, feeding, and spatial distribution in relation to bacterial population density remain under-explored. Here, we quantify the behavioural ecology of excavates using high-resolution, single-cell tracking and quantitative analysis. Focussing on two Discoba species – the marine Jakoba libera and freshwater Reclinomonas americana – we identify different behavioural patterns: J. libera swims, forages and feeds, while R. americana swims and feeds. Prey availability differentially affects motility: J. libera increases the number of swimming cells when food is scarce, while R. americana shows the opposite trend. Spatial statistics reveal fundamental differences in their feeding and redistribution strategies. J. libera acts as an active forager, whereas R. americana behaves as a strict filter feeder. A third species, the anaerobic Kipferlia bialata (from a different clade), adopts a foraging strategy similar to J. libera . Together, these results elucidate the adaptive relationship between prey availability, feeding modes, and motility in bacteriovorous excavate flagellates, offering new insights into the ecological and evolutionary dynamics of microbial predators. SIGNIFICANCE Microbial hunters and predators that feed on other small organisms play an important role in aquatic food webs. Many species are motile, with seemingly adaptive behaviours that are difficult to quantify. Here, we focus on different species of early-diverging biflagellates that share a common morphology consisting of two flagella and a feeding groove, which it uses to feed on surface-associated bacterial prey. We demonstrate how the predator’s behavioural profiles shift as prey abundance changes over many days of a culture cycle, accompanied by evolving patterns of spatial distribution. Species-specific differences provide insights into the mechanisms of environmental adaptation in early eukaryotes.
ER -