contractile vacuole

GO:0000331 · Membrane organelle · Membrane bounded organelle · Proposed

A specialized vacuole of eukaryotic cells, especially Protozoa, that fills with water from the cytoplasm and then discharges this externally by the opening of contractile vacuole pores. One of its functions is osmoregulatory. [GO:0000331]

Synonyms: CV; central bladder

Part of: contractile vacuole complex (GO:0062159)

Has part: contractile vacuolar membrane (GO:0031164)

Xrefs: uniprot.location:SL-0073 — Contractile vacuole

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
contractile vacuole V-ATPase	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Proton-pumping membrane complex that helps generate ion gradients needed to osmotically draw water into the contractile vacuole system. `DOI:10.1242/jcs.115.14.2893` Clarke et al. 2002 followed vacuolar H+-ATPase dynamics in the Dictyostelium contractile-vacuole complex. `DOI:10.1042/BC20070091` Nishihara et al. 2008 detected V-ATPase on vesicles around the Amoeba proteus contractile vacuole.
contractile vacuole aquaporins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Water channels on the contractile vacuole and associated vesicles that increase membrane water permeability during filling. `DOI:10.1042/BC20070091` Nishihara et al. 2008 cloned an Amoeba proteus aquaporin and localized it to the contractile vacuole membrane and perivacuolar vesicles. `DOI:10.1016/j.ejop.2024.126078` More et al. 2024 review membrane channels and receptors implicated in contractile-vacuole filling.

Taxonomic distribution

NCBITaxon:2759 Eukaryota — RARE: Contractile vacuoles occur patchily in unicellular eukaryotes, especially freshwater and soil protists, rather than throughout Eukaryota. [DOI:10.1016/j.ejop.2024.126078]

Canonical examples

NCBITaxon:44689 Dictyostelium discoideum — Amoebozoan model in which vacuolar H+-ATPase dynamics have been followed in the contractile-vacuole complex. [DOI:10.1242/jcs.115.14.2893]
NCBITaxon:3055 Chlamydomonas reinhardtii — Freshwater alga used to show that contractile vacuole size and pulse frequency respond to changing external osmolarity. [DOI:10.1128/EC.00163-14]
NCBITaxon:5693 Trypanosoma cruzi — Kinetoplastid parasite in which acidocalcisomes and the contractile-vacuole complex have been linked to hyposmotic-stress responses. [DOI:10.1074/jbc.M410372200]

Functions

osmoregulatory water expulsion — The contractile vacuole fills with excess cytosolic water and periodically discharges that water outside the cell to maintain volume and osmotic balance.
- DOI:10.1016/S0074-7696(02)15015-7 Allen and Naitoh 2002 review the contractile-vacuole cycle as the osmoregulatory route for expelling cytosolic water.
- DOI:10.1128/EC.00163-14 Komsic-Buchmann et al. 2014 quantified changes in Chlamydomonas contractile-vacuole pulse frequency and size under different osmotic conditions.

Mechanism graphs

Membrane pumps and water channels fill a contractile vacuole (FUNCTION)

Contractile-vacuole membrane proteins generate osmotic gradients and water permeability that fill the vacuole. The filled vacuole then rounds and discharges through a plasma-membrane pore.

Subject	Predicate	Object	Evidence
contractile vacuolar membrane	bounds	water-filled contractile vacuole	`GO:0031164` GO:0031164 defines the contractile vacuolar membrane as the lipid bilayer surrounding a contractile vacuole.
contractile vacuole V-ATPase	resides in	contractile vacuolar membrane	`DOI:10.1242/jcs.115.14.2893` Clarke et al. 2002 used GFP-tagged V-ATPase to track its dynamics in the Dictyostelium contractile-vacuole complex.
contractile vacuole V-ATPase	generates	osmotic gradient toward the vacuole lumen	`DOI:10.1042/BC20070091` Nishihara et al. 2008 interpreted V-ATPase-positive vesicles around the Amoeba contractile vacuole as participants in osmotic-gradient generation.
contractile vacuole aquaporins	increase water permeability of	contractile vacuolar membrane	`DOI:10.1042/BC20070091` Nishihara et al. 2008 localized Amoeba ApAQP to the contractile vacuole membrane and perivacuolar vesicles.
osmotic gradient toward the vacuole lumen	fills	water-filled contractile vacuole	`DOI:10.1016/S0074-7696(02)15015-7` Allen and Naitoh 2002 review fluid filling as a phase of the contractile-vacuole cycle.
water-filled contractile vacuole	discharges	external water discharge	`DOI:10.1128/EC.00163-14` Komsic-Buchmann et al. 2014 measured osmolarity-dependent pulse-frequency and size changes during contractile-vacuole function in Chlamydomonas.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for contractile-vacuole V-ATPase complexes and aquaporin components. V-ATPases and aquaporins are conserved protein families, but this first contractile-vacuole record does not pick a broad family CURIE without checking exact membership for the CV-localized subsets across Amoebozoa, algae and kinetoplastids.

Evidence

DOI:10.1016/S0074-7696(02)15015-7 Allen and Naitoh 2002, Osmoregulation and contractile vacuoles of protozoa, International Review of Cytology.
DOI:10.1242/jcs.115.14.2893 Clarke et al. 2002, Dynamics of the vacuolar H+-ATPase in the contractile vacuole complex and the endosomal pathway of Dictyostelium cells, Journal of Cell Science.
DOI:10.1042/BC20070091 Nishihara et al. 2008, Presence of aquaporin and V-ATPase on the contractile vacuole of Amoeba proteus, Biology of the Cell.
DOI:10.1128/EC.00163-14 Komsic-Buchmann, Wostehoff and Becker 2014, The contractile vacuole as a key regulator of cellular water flow in Chlamydomonas reinhardtii, Eukaryotic Cell.
DOI:10.1074/jbc.M410372200 Rohloff, Montalvetti and Docampo 2004, Acidocalcisomes and the contractile vacuole complex are involved in osmoregulation in Trypanosoma cruzi, Journal of Biological Chemistry.
DOI:10.1016/j.ejop.2024.126078 More et al. 2024, Contractile vacuoles: a rapidly expanding (and occasionally diminishing?) understanding, European Journal of Protistology.

Curation history

2026-09-10T08:06:33Z claude · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-10T08:08:50Z claude · EXPANDED_RECORD — Added GO complex parthood, contractile vacuolar membrane, V-ATPase and aquaporin components, eukaryotic taxonomic scope, Chlamydomonas, Dictyostelium and Trypanosoma canonical examples, a water-expulsion function, record-level evidence, a pump/channel-assisted filling graph, a UniProt SL xref and a channel-grounding discussion.
2026-09-10T08:12:02Z claude · EDITED_RECORD — Removed GO:0000331 grounding from the water-filled contractile vacuole graph node because that node denotes a transient filled state rather than an exact GO cellular-component class.
2026-09-10T08:19:54Z claude · EDITED_RECORD — Removed the contractile vacuolar membrane from molecular components because GO:0031164 is already represented as a membrane substructure in has_part; retained it as a grounded STRUCTURE node in the function graph.

Source: data/structures/membrane_organelle/contractile_vacuole.yaml