[2] Foraminiferans are single-celled lifeforms, and Marginopora vertebralis is exceptionally large, forming discs that can be 1.5 to 2 cm (0.6 to 0.8 in) in diameter, or even larger.

The test or calcareous shell is secreted by the foram, and is surrounded by the cell membrane, a thin layer of cytoplasm.

[2] Marginopora vertebralis is host to symbiotic zooxanthellae, most commonly Gymnodinium rotundatum, which are present in large numbers in the protoplasm, and give the living foraminiferan its colour.

It feeds on the diatoms, microalgae and fragments of organic detritus that are within reach of its pseudopodia, absorbing them by phagocytosis.

When fish graze on the algae and sea grasses to which the foraminiferan is attached, they usually pass through the gut unaffected.