Ctenophores are commonly called "comb jellies" because they have rows of cilia that are fused at the base, giving them an appearance like a comb. These organisms are diploblasts like jellyfish (cnidarians) and once were thought to be very closely related to them. Turns out that part of that assumption came from the fact that one genus, Haeckelia, had cnidocytes, stinging cells that jellyfish use to capture prey. Recently, though, it was discovered that Haeckelia was getting their cnidocytes not by developing them, but from stealing them from jellyfish that they were eating. A while ago, we met a parasitic jellyfish and Lampea pancerina is thought to be the only parasitic ctenophore. The young comb jellies live inside tunicates, but not much is known about this relationship.
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