Stalk spasmoneme

cellstructuremech:stalk_spasmoneme · Cytoskeleton · Other · Proposed

An intracellular contractile fibrillar organelle within the stalk of contractile-stalk peritrich ciliates. A spasmin-rich fibrillar mass is interspersed with membrane-bounded tubules. Shortening deforms the surrounding stalk; the organelle is distinct from the extracellular sheath and from the continuous body myoneme network. [DOI:10.1083/jcb.77.2.358]

Vorticella convallaria spasmoneme profile with membrane-bounded tubules and adjacent cortical structures. Unmodified source-served TEM preview by Richard Allen. This image shows morphology, not protein-specific localization or a calcium-transport measurement; no calibrated dimensions are inferred from the preview. TEM · Vorticella convallaria (NCBITaxon:60850) · Richard Allen (University of Hawaii); via Cell Image Library · PUBLIC_DOMAIN · source: CELL_IMAGE_LIBRARY CIL:39509 · DOI:10.7295/W9CIL39509

Synonyms: vorticellid spasmoneme; stalk myoneme; spasmoneme

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
Centrin/spasmin-family proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Calcium-binding constituents of the stalk contractile organelle. This combined family-level class does not assert one gene product, an exhaustive inventory, native filament sufficiency or individual assembly requirements. `DOI:10.1083/jcb.77.2.358` Spasmin-rich protein fractions were obtained from denuded stalks and dissected spasmonemes; additional proteins remained unidentified. `DOI:10.1111/j.1550-7408.1999.tb04601.x` Abstract reports a cloned V. convallaria spasmin, recombinant calcium binding and 1F5 immunolocalization; full methods were not read. `https://ilacadofsci.com/wp-content/uploads/2013/03/102-15MS2905-print.pdf` Immunogold localizes centrin/spasmin immunoreactivities within the spasmoneme. N-termVcCentrin4 labels fibrillar and tubular compartments; 1F5 labeling favors the fibrillar mass.

Canonical examples

NCBITaxon:60850 Vorticella convallaria — Live-cell microfluidic experiments characterize load-dependent stalk contraction. Separately cited CIL:39509 provides imaging of this species. No strain CURIE or genus-wide prevalence is asserted. [DOI:10.1016/j.bpj.2012.07.038]
NCBITaxon:168244 Carchesium polypinum — Species used for cultured, denuded-stalk protein preparations and calcium-dependent assays; not a claim about all colonial peritrichs. [DOI:10.1083/jcb.77.2.358]

Functions

Calcium-responsive stalk contraction — Spasmoneme shortening drives deformation of the surrounding stalk and retraction of the attached cell body. Geometry and external resistance affect the observed movement; no universal contraction speed or force is asserted.
- DOI:10.1083/jcb.77.2.358 Glycerinated preparations respond reversibly to calcium exposure and removal.
- DOI:10.1016/j.bpj.2012.07.038 Greater imposed viscous resistance slows live V. convallaria contraction and reduces its excursion. Force values require hydrodynamic inference and extrapolation.

Mechanism graphs

Observed stalk contractile response (FUNCTION)

Qualitative organelle-level response, not a resolved molecular motor cycle.

Subject	Predicate	Object	Evidence
Calcium exposure of glycerinated preparations	elicits	Spasmoneme shortening	`DOI:10.1083/jcb.77.2.358` Calcium-responsive glycerinated organelles; not a live-cell channel mechanism.
Spasmoneme shortening	drives	Stalk deformation and cell-body retraction	`DOI:10.1016/j.bpj.2012.07.038` Contractile stalk mechanics connect organelle shortening with cell-body displacement.
Imposed viscous resistance in live Vorticella	slows and limits	Stalk deformation and cell-body retraction	`DOI:10.1016/j.bpj.2012.07.038` Controlled channel-flow resistance increases contraction duration and decreases excursion.

Discussions

CURATION_TODO (RESOLVED): Separate the stalk organelle from body myonemes and the complete stalk. Continuity, related proteins and historical terminology do not make these structures identical.
CURATION_TODO (OPEN): Resolve the native constituent inventory, exact family groundings and proposed scaffold partners. Protein enrichment and chemical perturbation do not establish a complete molecular assembly.
CURATION_TODO (RESOLVED): Preserve antibody specificity and sample-preparation limits. Compartment labeling cannot be treated as an isoform-specific native molecular reconstruction.
CURATION_TODO (RESOLVED): Keep the extracellular sheath and unresolved calcium-handling machinery outside the molecular component list. An observed compartment or neighboring structure is not an identified protein family.
CURATION_TODO (OPEN): Resolve the native contraction and recovery mechanism without promoting physical models to molecular observations. Measured displacement, inferred force and simulated motor arrangements answer different questions.
CURATION_TODO (OPEN): Resolve the historical Zoothamnium geniculatum name at a taxonomic authority. A historical experimental organism must not receive a guessed modern taxon identifier.
CURATION_TODO (RESOLVED): Keep the source preview distinct from quantitative microscopy and protein-specific localization. An unlabeled TEM preview cannot establish protein identity, calcium transport or calibrated dimensions.

Evidence

DOI:10.1083/jcb.77.2.358 Routledge (1978). Read the full 13-page primary PDF, including Methods, Results, Discussion and legends. Versioned PMC2110051.1 PDF checksum verified; JATS has only abstract and reference text.
DOI:10.1111/j.1550-7408.1999.tb04601.x Maciejewski et al. (1999). PubMed/Europe PMC abstract and identity verified; the available full-text route is subscription-only.
https://ilacadofsci.com/wp-content/uploads/2013/03/102-15MS2905-print.pdf Konior, McCutcheon and Buhse (2009), Transactions of the Illinois State Academy of Science 102:161-174. Read all main text and figure legends in the publisher-hosted PDF.
DOI:10.1016/j.bpj.2012.07.038 Ryu, Lang and Matsudaira (2012). Read the complete eight-page author-hosted article, not its Supporting Material.
DOI:10.1111/j.1550-7408.1998.tb05066.x Asai et al. (1998). Publisher abstract read; no claim to have read full experimental methods.
DOI:10.1111/jeu.70006 Jiang et al. (2025). Primary abstract and metadata read; complete publisher text was not accessible through the checked routes.
DOI:10.7295/W9CIL39509 Single-item CIL metadata and unmodified preview inspected; public-domain dedication, author, organism and source-served preview verified.
GO:0005622 Verified non-obsolete intracellular anatomical structure, used only as a broad is-a parent.

Curation history

2026-10-03T22:30:52Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-03T22:33:02Z codex · EXPANDED_RECORD — Added primary evidence, a source-neutral centrin/spasmin class, verified examples, scoped functional response graph, assay/model/taxon limits and a checksum-verified public-domain CIL preview.
2026-10-03T22:50:29Z codex · CORRECTED_EVIDENCE_SCOPE — Addressed issue #2002: distinguish abstract-supported stalk CCDC/EGF-like membership from CCDC-specific sheath localization; preserve the spasmoneme exclusion, discussion rationale and dates.

Source: data/structures/cytoskeleton/stalk_spasmoneme.yaml