Nerve-net
Guides
Ctenophora
comb jellies, sea gooseberries, sea walnuts, Venus's girdles
Ctenophora is a phylum of marine invertebrates distinguished by eight rows of fused cilia used for locomotion, called comb rows. They are the largest animals to swim using cilia. Unlike cnidarians, they lack stinging cells and instead capture prey using colloblasts—sticky adhesive cells. The phylum contains approximately 150–186 recognized species exhibiting diverse body plans, from egg-shaped cydippids with retractable tentacles to flattened benthic platyctenids and large-mouthed beroids. Ctenophores possess a decentralized nerve net without a brain, and their phylogenetic position as either the earliest or second-earliest branching animal lineage remains actively debated.