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How do sea squirts differ from larvaceans?

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A translucent X-ray fish (Pristella maxillaris) swims in an aquarium, showing its visible backbone and internal structures through its body. — Chordate X-ray fish (*Pristella maxillaris*), is an example of a chordate with a visible backbone.

Sea squirts and larvaceans are both members of the subphylum Tunicata, but they differ significantly in their lifestyle, structure, and development:

Habitat and Lifestyle: Sea squirts (class Ascidiacea) are primarily benthic and sedentary as adults, often forming colonies. In contrast, larvaceans (class Appendicularia) are pelagic, spending their entire lives in the open sea, and they do not form colonies.123
Body Structure: While the adult sea squirt undergoes metamorphosis into a sedentary form with reduced nervous and muscular systems, the adult larvacean retains a tadpolelike body that resembles the larval form of other tunicates.312
Feeding: Larvaceans are unique for secreting a delicate, gelatinous "house" around their bodies, which they use to net food particles from the water. They frequently abandon these structures to secrete new ones throughout the day.31

Both groups are classified as protochordates, sharing fundamental chordate characteristics such as a notochord, a hollow dorsal nerve cord, and gill slits.4