identifier: traitmech:000655
label: coenobium formation
definition: A morphological phenotype in which an alga forms clonal multicellular
  colonies whose cell complement is established during colony formation, with subsequent
  colony growth by cell enlargement rather than addition of cells.
definition_source: DOI:10.1098/rspb.2023.1882
trait_category: MORPHOLOGY
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- METPO:1000059
evidence:
- reference: DOI:10.1098/rspb.2023.1882
  snippet: characteristically form clonal colonies of fixed cell number known as coenobia.
  notes: Harvey (2023), PMID:37876191, PMC10598416, Comparisons with extant taxa.
    Direct full-text terminology passage covers Volvocales, Scenedesmaceae and Hydrodictyaceae.
    Growth after colony formation is by cell expansion; a later reproductive cycle
    makes daughter colonies. This comparison supports terminology, not a new experiment
    on living algae; the paper's fossil developmental reconstruction remains an inference.
- reference: DOI:10.1242/jcs.212233
  snippet: progeny were unicellular in three species and multicellular (joined in
    a sheet-like coenobium) in two.
  notes: Cardon et al. (2018), PMID:29487180, scientific abstract. Primary Results,
    Methods and actual Figure 1 were inspected. The coenobial species are Enallax
    costatus and Tetradesmus obliquus; multiple fission occurs in all five tested
    species and alone does not establish coenobial progeny. Figure 1 supports joined-cell
    morphology. Release is author-reported in the Results, not visible in Figure 3;
    supplementary Figure S1 and movies were not directly inspected.
- reference: DOI:10.1038/s41598-018-28627-z
  snippet: monocultures of D. opoliensis in the control groups (without IAA treatment)
    were dominated by two-celled and four-celled coenobia
  notes: Chung et al. (2018), PMID:29980731, PMC6035231, Results. Direct full text
    reports this morphology after one week; Methods describes native isolates cultured
    in CA medium. Higher indole-3-acetic acid concentrations favor unicells in the
    tested monocultures, so IAA is not a universal coenobium inducer. No percentage,
    causal protein claim or direct figure inspection is asserted here.
canonical_examples:
- taxon_id: NCBITaxon:113528
  taxon_label: Enallax costatus
  reference: DOI:10.1242/jcs.212233
  note: 'CCAP 276/31 (paper: CCAP 276-31), grown at 25 C on a 12:12 light/dark cycle
    in a 1:1 mixture of Bold''s basal medium with micronutrients and Woods Hole medium.
    Figure 1 and Results document coenobial morphology, not an invariant state for
    every life stage. Collection provenance at https://www.ccap.ac.uk/catalogue/strain-276-31
    identifies Hegewald''s 1980 Finnish lake isolate and lists GMO: No. The paper
    describes unialgal cultures, not axenic cultures.'
discussions:
- discussion_id: coenobium-formation-scope-and-hierarchy
  prompt: Review a multicellular morphology parent and exact mappings.
  kind: CURATION_TODO
  status: OPEN
  rationale: Retain phenotype METPO:1000059. Cell shape METPO:1000666 is individual-cell
    morphology; colony morphology METPO:1007062 concerns macroscopic colony characteristics.
    Obsolete cell arrangement METPO:1000046 and aggregate METPO:1000011 are not active
    parents. Palmelloid formation traitmech:000654 covers mother-wall retention or
    extracellular adhesion, not this developmental cell-complement criterion. Rosette
    cell arrangement traitmech:000652 requires inward cell poles, and biofilm formation
    traitmech:000053 requires surface attachment; neither is required here. A coenocyte
    is a multinucleate cell, not a multicellular coenobium. No exact synonym, xref
    or organism-level disjointness is asserted.
  posed_by: codex
  posed_date: '2026-10-07'
- discussion_id: coenobium-formation-development-and-mechanism
  prompt: Resolve organism-specific colony development before graphing.
  kind: KNOWLEDGE_GAP
  status: OPEN
  rationale: 'Fixed cell complement describes an individual colony, not one invariant
    count across taxa or conditions. Reproduction can form new daughter colonies.
    Harvey''s extant comparisons include motile forms and Volvox germ-soma differentiation;
    Chung''s introductory little-or-no-specialization formulation is not imposed universally.
    Neither a sheet shape, common wall, power-of-two count, lack of flagella nor grazer
    induction defines the class. Defer a causal graph pending perturbation and accession-level
    evidence: Cardon''s observed Golgi localization and cell rotation do not demonstrate
    causal necessity for coenobium formation. Gene possession alone does not establish
    this phenotype.'
  posed_by: codex
  posed_date: '2026-10-07'
curation_history:
- timestamp: '2026-10-07T01:56:55Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Added coenobium formation with three DOI-backed snippets, a qualified Enallax
    costatus example and developmental scope boundaries. Ignored-and-hidden searches
    and structured METPO review found no exact record. Reserved METPO:1060800 in v531;
    existing records unchanged.
  llm_assisted: true