AbstractCnidarians, as model animals for studying conserved feeding behavior, possess the simplest nervous and digestive systems. Feeding behavior in cnidarians begins with nematocyst-mediated prey retention, proceeds to coordinated tentacle movements and mouth opening, and then proceeds to release of retained prey for ingestion. Understanding the basis of nematocyst discharge, retention, and release is central to explaining cnidarian feeding. Based on studies using artificial targets, cnidocyte supporting cell complexes (CSCCs) regulate nematocyst discharge, retention, and release in Actinaria (sea anemones); but the relevance of CSCCs to prey retention and ingestion has not yet been established. CSCCs exist as three functional types (Types A, B, and C), with a ratio of Types A∶B∶C of 2∶2∶1 in Diadumene lineata (a.k.a. Haliplanella luciae). We tested the hypothesis that CSCCs control nematocyst-mediated prey killing and ingestion. We used a quantitative feeding assay involving Artemia nauplii (prey) and monoclonal D. lineata. The ratios of Types A∶B∶C involved in prey killing and ingestion were 1∶2.5∶5 and 1∶2∶3, respectively. These findings support the CSCC hypothesis. They also indicate that Type Cs predominate in killing small, hard-surfaced, motile, crustaceous prey. Chemoreceptor-bearing Type Bs and Type As assist in prey killing and assume somewhat greater roles in ingestion. Thus, CSCC types differ with respect to their afferent sensory roles as well as their subsequent efferent roles in killing and ingestion. We conclude that CSCC types perform overlapping and complementary roles during feeding.