gilled

Gilled describes something that has gills—the respiratory organs that allow fish and other aquatic creatures to extract oxygen from water.

A gilled fish breathes underwater through slits on the sides of its head.

The term extends to mushrooms, where gilled refers to the thin, blade-like structures radiating from the underside of the cap: Most edible mushrooms are gilled varieties.

In both cases, gilled points to a distinctive structural feature involving parallel plates or openings.