funis

cellstructuremech:funis · Cytoskeleton · Other · Proposed

A Giardia trophozoite cytoskeletal structure composed of short microtubule arrays that emanate from the caudal flagellar axonemes, anchor to dense rods running parallel to the posterior-lateral flagella, and after posterior-lateral flagellar emergence anchor to the epiplasm beneath the contractile tail membrane. [DOI:10.1016/j.jsb.2004.01.017]

Part of: GO:0005856 — cytoskeleton (no local record)

Has part: microtubule (GO:0005874)

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
alpha- and beta-tubulins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Tubulin constituents that polymerize into the short funis microtubule arrays of Giardia trophozoites. `GO:0005874` Gene Ontology defines microtubules as tubes of polymeric tubulin. `DOI:10.1016/j.jsb.2004.01.017` Benchimol et al. 2004 used high-resolution field-emission scanning electron microscopy to show that the Giardia funis is made of short microtubule arrays.

Taxonomic distribution

NCBITaxon:5741 Giardia intestinalis — COMMON: Giardia intestinalis trophozoites carry funis microtubule arrays emanating from the caudal flagellar axonemes in the posterior cell body. [DOI:10.1016/j.jsb.2004.01.017]

Canonical examples

NCBITaxon:5741 Giardia intestinalis — Parasitic diplomonad model in which the funis was characterized by high-resolution field-emission scanning electron microscopy. [DOI:10.1016/j.jsb.2004.01.017]

Mechanism graphs

Funis microtubules link Giardia flagellar axonemes to the tail cortex (FUNCTION)

In Giardia trophozoites, short funis microtubule arrays emanate from the caudal flagellar axonemes, anchor to dense rods running parallel to the posterior-lateral flagella, and anchor to the epiplasm beneath the contractile tail membrane after posterior-lateral flagellar emergence.

Subject	Predicate	Object	Evidence
alpha- and beta-tubulins	polymerize into	funis	`GO:0005874` Gene Ontology defines microtubules as polymeric tubulin tubes. `DOI:10.1016/j.jsb.2004.01.017` Benchimol et al. 2004 described the funis as short arrays of microtubules.
funis	emanates from	caudal flagellar axonemes	`DOI:10.1016/j.jsb.2004.01.017` Benchimol et al. 2004 found funis microtubule arrays emanating from caudal flagellar axonemes.
funis-associated dense rods	anchor	funis	`DOI:10.1016/j.jsb.2004.01.017` Benchimol et al. 2004 observed funis microtubules anchored to dense rods that run parallel to the posterior-lateral flagella.
funis	anchors to	Giardia epiplasm	`DOI:10.1016/j.jsb.2004.01.017` Benchimol et al. 2004 placed funis microtubule anchors at the epiplasm underlying the contractile membrane region after posterior-lateral flagellar emergence.
funis	is proposed to support	Giardia tail flexion	`DOI:10.1016/j.jsb.2004.01.017` Benchimol et al. 2004 proposed a model for Giardia tail flexion based on funis ultrastructure.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings and boundaries for funis tubulins, dense rods, epiplasm-associated anchors and any additional funis-associated proteins. The funis is a Giardia microtubule array associated with dense rods and the epiplasm, but this pass did not identify exact molecular components for those associated structures.
CURATION_TODO (OPEN): Test the proposed role of the funis in Giardia tail flexion before asserting a mature biological-process function. The first funis record captures the published ultrastructural model for tail flexion without overclaiming a genetic perturbation or fully resolved contractility mechanism.

Evidence

DOI:10.1016/j.jsb.2004.01.017 Benchimol, Piva, Campanati and de Souza 2004, Visualization of the funis of Giardia lamblia by high-resolution field emission scanning electron microscopy: new insights, Journal of Structural Biology.
DOI:10.1016/bs.apar.2019.11.001 Microtubule organelles in Giardia, Advances in Parasitology.
GO:0005622 Intracellular anatomical structure is a broader is-a class for the Giardia funis, without equating it to one microtubule or the whole cytoskeleton.
GO:0005856 — cytoskeleton Cytoskeleton denotes the containing cellular framework. Benchimol et al. 2004 describe funis as one of several microtubular structures composing the Giardia cytoskeleton, supporting part_of rather than is-a.

Curation history

2026-09-22T09:17:02Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-22T09:18:00Z codex · EXPANDED_RECORD — Added cytoskeleton parentage, microtubule parthood, a label-only alpha/beta tubulin component, Giardia intestinalis scope, DOI evidence, a nonmechanistic funis topology graph, and open TODOs for dense-rod grounding and tail-flexion mechanism.
2026-10-12T00:29:13Z codex · ADDRESS_SAVED_REVIEW — Addressed #2273: represented cytoskeleton as a containing whole via part_of, corrected relationship evidence, and preserved exact structure identity and all existing biological claims.

Source: data/structures/cytoskeleton/funis.yaml