identifier: traitmech:000585
label: gravikinesis
definition: A motile phenotype in which the speed of active propulsion is modulated
  according to orientation relative to gravity.
definition_source: DOI:10.2187/bss.20.44
trait_category: PHYSIOLOGY
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- METPO:1000702
evidence:
- reference: DOI:10.2187/bss.20.44
  snippet: We confirmed the gravikinesis from the analysis on the swimming of single
    cells.
  notes: Abstract; full publisher PDF inspected at https://www.jstage.jst.go.jp/article/bss/20/2/20_2_44/_pdf.
    Methods and Results (pages 45-46, Table 1) distinguish active propulsion from
    passive drift using subsequent 10-18 mM NiCl2 immobilization of the same cell.
    The drift controls retained contractile-vacuole activity and lacked visible deformation.
    Curved-swimmer responses reverse in 72% Percoll; straight-swimmer responses were
    not significant. Results N=55 and Table 1 straight-swimmer N=57 are unreconciled;
    no aggregate sample count is asserted. Table and method pages were visually checked.
- reference: DOI:10.1007/s001140050634
  snippet: The resulting potential-induced modulation of the speed of propulsion is
    called gravikinesis because it acts to neutralize, fully or in part, sedimentation.
  notes: Publisher abstract and Europe PMC PMID:11536922 checked. Orientation-dependent
    membrane-potential changes support a physiological component of propulsion control
    in Paramecium. The sedimentation-opposing response described here is not a universal
    sign convention or proof of one receptor in all taxa. The subscription full text
    was not inspected; no strain, channel accession or full-text-only measurement
    is inferred.
canonical_examples:
- taxon_id: NCBITaxon:5885
  taxon_label: Paramecium caudatum
  reference: DOI:10.2187/bss.20.44
  note: Curved-swimming cells from 14-20-day early-stationary hay-infusion cultures
    at 24 C, adapted to KCM (pH 7.2) and selected beneath the water surface. Table
    1 supports gravity-dependent active propulsion in the control hypo-density medium.
    Swimming was recorded before nickel immobilization, which supplied only the passive-drift
    correction. This is not a universal cell-state claim. NCBI identifier is species-level;
    no strain accession is supplied.
discussions:
- discussion_id: gravikinesis-speed-and-direction-boundaries
  prompt: Keep propulsion modulation distinct from orientation and passive drift.
  kind: CURATION_TODO
  status: OPEN
  rationale: Observed upward/downward speed differences alone can arise from sedimentation
    or flotation; the trait concerns the active propulsion component. Gravitaxis (traitmech:000584)
    denotes directional bias, and gyrotaxis (traitmech:000583) denotes torque-mediated
    orientation. These can coexist with gravikinesis; no equivalence, disjointness
    or parent-child relation among them is asserted. The definition does not require
    faster upward swimming in every medium. Reconcile sign conventions and source-qualified
    response classes before adding narrower terms or equivalent external mappings.
  posed_by: codex
  posed_date: '2026-10-04'
- discussion_id: gravikinesis-mechanism-grounding
  prompt: Resolve exact protein and taxon anchors for a mechanistic graph.
  kind: CURATION_TODO
  status: OPEN
  rationale: 'Mechanism evidence exists: Gebauer''s abstract links orientation to
    membrane potential and propulsion, while Takeda discusses mechanosensitive conductances
    and ciliary control. The inspected sources do not identify a sequence-resolved
    gravity receptor. Takeda treats hydraulic pressure as a candidate stimulus needing
    amplification, not a demonstrated complete molecular pathway. A graph is deferred
    pending eligible taxon-paired protein examples and source-bounded causal edges.
    Do not substitute an unrelated channel or classify this physiological mechanism
    as NONMECHANISTIC to avoid the protein-coverage gate.'
  posed_by: codex
  posed_date: '2026-10-04'
curation_history:
- timestamp: '2026-10-04T03:19:30Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Added gravikinesis with two primary DOI sources, contiguous snippets and
    a drift-corrected Paramecium caudatum example at verified species taxon 5885.
    Ignored-and-hidden searches found only gravitaxis boundary mentions, not an exact
    trait or METPO term. Reserved METPO:1053900 in proposal v462; kept direction,
    passive drift, source sample counts and unresolved protein-level mechanism separate.
  llm_assisted: true