[4] The denseness of their celestite ensures acantharian shells function as mineral ballast, resulting in fast sedimentation to bathypelagic depths.

Acantharians are unique among marine organisms for their ability to biomineralize strontium sulfate as the main component of their skeletons.

The endoplasm, at the core of the cell, contains the main organelles, including many nuclei, and is delineated from the ectoplasm by a capsular wall made of a microfibril mesh.

The ectoplasm is surrounded by a periplasmic cortex, also made up of microfibrils, but arranged into twenty plates, each with a hole through which one spicule projects.

The cortex is linked to the spines by contractile myonemes, which assist in buoyancy control by allowing the ectoplasm to expand and contract, increasing and decreasing the total volume of the cell.

[11] The morphological classification system roughly agrees with phylogenetic trees based on the alignment of ribosomal RNA genes, although the groups are mostly polyphyletic.

The relationship may make it possible for acantharians to be abundant in low-nutrient regions of the oceans and may also provide extra energy necessary to maintain their elaborate strontium sulfate skeletons.

[12] Symbiotic Holacanthida acantharians host diverse symbiont assemblages, including several genera of dinoflagellates (Pelagodinium, Heterocapsa, Scrippsiella, Azadinium) and a haptophyte (Chrysochromulina).