Clonal-aggregative multicellularity tuned by salinity in a choanoflagellate
Article Date: 25 February 2026
Article URL: https://www.nature.com/articles/s41586-026-10137-y
Article Image: Figure 1
Summary
This Nature study characterises an unexpected mixed mode of multicellularity in the choanoflagellate C. flexa: colonies (curved cell sheets) form both by serial cell division (clonal) and by active aggregation of free-swimming cells, a combination the authors call clonal-aggregative multicellularity. Field surveys in Curaçao splash pools show that salinity controls the switch: low-to-moderate salinity supports multicellular feeding sheets, while hypersalinity (during evaporation) triggers sheet dissociation, encystation into desiccation-resistant single cells and persistence in soil. Rehydration restores flagellates that reform sheets by both mechanisms. Aggregative sheets are functional (they invert with light changes and capture more bacteria per cell than singletons), aggregation is active and species/kin-biased, and genomic comparisons identify candidate adhesion/signalling loci (including a polymorphic cadherin) that may underlie kin recognition.
Key Points
- C. flexa forms multicellular sheets via serial cell division and by active aggregation — a mixed clonal-aggregative strategy.
- Salinity is the environmental switch: sheets occur below a threshold (~<94 ppt in field surveys); hypersalinity causes sheet dissociation and encystation.
- Encysted single cells survive desiccation in soil and, after rehydration, regenerate sheets through both division and aggregation.
- Aggregation is active (requires live cells and intact microvilli), can produce chimeric but species- and kin-biased sheets, and cells rearrange to form polarised monolayers within 24 h.
- Multicellular sheets capture >2× bacteria per cell versus unicells at permissive salinity — a feeding advantage for the multicellular form.
- Genome sequencing and strain comparisons reveal polymorphic candidates (adhesion domains, a cadherin-like locus and receptor kinases) with signs of diversifying selection consistent with kin recognition.
- Environmental parameters (salinity, cell density) tune the relative contributions of clonality versus aggregation, allowing robustness across fluctuating splash-pool habitats.
Context and Relevance
This work links ecology, cell biology and genomics to show how a natural, cyclical stress (evaporation/refilling and salinity swings) can entrain a life cycle that alternates between multicellularity and unicellularity. The findings matter for understanding how different routes to multicellularity (clonal vs aggregative) can coexist and be adaptively regulated — with implications for hypotheses about the origins of animal multicellularity and for how environmental scaffolding can shape life-cycle evolution. Using field data plus mechanistic lab work and genome analyses gives the study strong ecological and evolutionary credibility.
Why should I read this?
Short version: it’s neat and a bit surprising. These researchers found a choanoflagellate that can be multicellular two different ways and flips between them depending on salt. If you care about how multicellularity can arise and stick around in messy real-world habitats, this paper packs field work, microscopy, experiments and genomics into one tidy package — we’ve done the skimming for you, but the full paper is worth a proper read if you want the methods and candidate genes.
Author style
Punchy: This paper is a must-see for evo‑biologists and microbial ecologists — it reframes the neat dichotomy between clonal and aggregative multicellularity as a flexible spectrum controlled by environment. If you follow the evolution of complex life histories or the ecological drivers of multicellularity, read the main text and methods closely: the field–lab–genomics interplay is where the real insights live.