1. Plural of ambulacrum; radial grooves or channels on the surface of echinoderms (such as starfish and sea urchins) that contain tube feet used for movement and feeding.
Usage: technical; biology; plural form

Examples

• The starfish uses its ambulacra to move slowly across the ocean floor.
• Sea urchins have five ambulacra arranged in a radial pattern.
• The tube feet within the ambulacra help the echinoderm grip surfaces.
• Marine biologists examined the ambulacra under a microscope to study the creature's locomotion.
• Each ambulacrum contains hundreds of tiny suction-cup-like tube feet.