identifier: traitmech:000584
label: gravitaxis
definition: A motile phenotype in which the direction of active swimming is biased
  relative to gravity.
definition_source: DOI:10.1038/s41598-018-26046-8
trait_category: PHYSIOLOGY
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- METPO:1000702
evidence:
- reference: DOI:10.1038/s41598-018-26046-8
  snippet: Predominantly, E. gracilis shows a negative gravitaxis behavior.
  notes: Introduction, page 1, visually verified at https://d-nb.info/1186379677/34
    (PMID:29765103; PMC5954063). Direction varies with culture age. Results, Figure
    4 and Supplementary Figure 6e-g distinguish upward-biased controls from EgPCDUF4201/CaM2
    knockdowns. Full main text and supplement 41598_2018_26046_MOESM1_ESM.pdf inspected
    via Europe PMC. Supplementary Figure 5e, not the main text's 5c, measures flagellar
    length; Supplementary Table 1 reports comparable, not identical, speeds. These
    controls do not exclude every flagellar defect. PKA phosphorylation and a direct
    dynein link remain hypotheses.
- reference: DOI:10.1242/jeb.050666
  snippet: the ability to swim preferentially upwards (negative gravitaxis) is primarily
    the result of upwardly curving trajectories
  notes: Summary (PMID:21112996); publisher main-text Methods, Results and Discussion
    inspected. Curved trajectories agree with a physical shape-orientation model,
    but shape and orientation rate were not measured simultaneously in the same individual.
    This is not proof that all protists lack gravity receptors. Gravikinesis concerns
    orientation-dependent swimming speed, not the directional phenotype. Equation
    images and supplementary material were not inspected; no equation-derived or supplement-only
    claim is asserted.
canonical_examples:
- taxon_id: NCBITaxon:3039
  taxon_label: Euglena gracilis
  reference: DOI:10.1038/s41598-018-26046-8
  note: Strain Z, axenic organic-medium cultures at 20 C under continuous light. Figure
    4a and Supplementary Figure 6e show upward-biased wild-type controls; Methods
    specify buffer-only electroporation. These are not the RNAi knockdowns. NCBI identifier
    is species-level, not a strain accession; no universal age-independent direction
    is implied.
- taxon_id: NCBITaxon:5885
  taxon_label: Paramecium caudatum
  reference: DOI:10.1242/jeb.050666
  note: Wild-type cells from one-week-old boiled-hay-infusion cultures. After several
    hours in the observation chamber, rotation of the chamber revealed upward-curving
    swimming tracks (Results, Figure 2). NCBI identifier is species-level; the paper
    does not supply a resolved strain accession.
discussions:
- discussion_id: gravitaxis-direction-and-process-boundaries
  prompt: Keep gravity-relative swimming distinct from settling and neighboring traits.
  kind: CURATION_TODO
  status: OPEN
  rationale: 'Positive and negative gravitaxis are directional cases, not a requirement
    that all cells always swim upward. Passive settling alone and speed changes alone
    do not establish this trait. The definition does not require an active gravity
    receptor: powered swimming and physical orientation can coexist. Gyrotaxis (traitmech:000583)
    specifies a gravity-viscous torque mechanism, not an exact synonym or a disjoint
    phenotype. No new subsumption axiom between them is asserted without reviewing
    both scopes. QuickGO resolved active GO:0042332 gravitaxis on 2026-10-04, including
    geotaxis as an exact lexical synonym. It denotes a biological process rather than
    this organismal disposition; keep it out of equivalent xrefs and resolve any mapping
    separately.'
  posed_by: codex
  posed_date: '2026-10-04'
- discussion_id: gravitaxis-mechanism-grounding
  prompt: Resolve exact protein anchors and a faithful physical-mechanism graph.
  kind: CURATION_TODO
  status: OPEN
  rationale: The sources provide mechanism evidence, but this first record does not
    yet include a graph. Nasir's CaM2 accession EU935858 resolves to UniProtKB:B5THA2,
    an unreviewed entry without a Proteomes cross-reference in the 2026-10-04 REST
    response. An exact EgPCDUF4201 name query returned no hit; this does not establish
    sequence absence. Resolve eligible exact examples before adding the molecular
    branch; a DUF4201 match alone does not demonstrate gravitaxis. For the physical
    branch, the current MECHANISTIC coverage audit requires a protein node and example.
    Do not invent a receptor or misclassify physical causation as NONMECHANISTIC to
    satisfy that audit.
  posed_by: codex
  posed_date: '2026-10-04'
curation_history:
- timestamp: '2026-10-04T02:18:15Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Added gravitaxis with two primary DOI sources, contiguous snippets and
    source-qualified examples at verified species taxa 3039 and 5885. Ignored-and-hidden
    searches found only gyrotaxis boundary mentions, not an exact record or METPO
    term. Reserved METPO:1053800 in proposal v461; documented process-grain and mechanism-grounding
    gaps without substituting a protein or asserting a universal receptor.
  llm_assisted: true