The Order Actinulida is a group of minute, free-living marine hydrozoans within the class Hydrozoa (Phylum Cnidaria). These organisms are typically microscopic and worm-like, living interstitially in marine sediments. Actinulids lack a prominent polyp stage and spend most of their life as free-swimming medusoid forms. They possess simple tentacles and a nerve net for capturing tiny prey, primarily plankton. Despite their small size, they play a role in benthic ecosystems as part of the microfaunal food web, contributing to nutrient cycling in marine environments.