1. Plural of pneumatocyst; gas-filled bladders or chambers found in certain marine organisms, especially siphonophores and some seaweeds, that provide buoyancy.
Usage: technical; biology; marine science

Examples

• The Portuguese man o' war uses pneumatocysts to stay afloat on the ocean surface.
• Pneumatocysts in siphonophores are specialized structures that regulate buoyancy.
• Marine biologists study pneumatocysts to understand how colonial organisms maintain their position in the water column.
• The pneumatocysts of certain kelp species help the fronds float toward sunlight.
• Without functional pneumatocysts, many pelagic organisms would sink to the ocean floor.