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How do adult appendicularians resemble tunicate larvae?

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Bright blue sea squirt Rhopalaea crassa with yellow-edged openings grows on a coral reef among various corals in the Philippines. — tunicate Blue spot sea squirt (*Clavelina moluccensis*), a colonial tunicate.

Adult appendicularians (also known as larvaceans) resemble the tadpole larvae of other tunicates, such as sea squirts, because they retain juvenile features throughout their lives.123

This phenomenon is known as paedomorphosis, which occurred as appendicularians evolved to reach sexual maturity before undergoing the metamorphosis that typically causes other tunicates to lose their larval characteristics. While typical tunicate larvae possess a notochord, a dorsal nerve cord, and a muscular tail—features they usually resorb upon settling and attaching to a substrate—adult appendicularians maintain a similar tadpole-like body structure consisting of a trunk and a tail. Unlike their sessile relatives, appendicularians remain free-swimming in the open sea, continuing to use their tail for locomotion and to generate currents for feeding within a specialized gelatinous "house".456213