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How do larvaceans resemble the larvae of sea squirts?
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Chordate
X-ray fish (Pristella maxillaris), is an example of a chordate with a visible backbone.
Larvaceans are members of the class Appendicularia that live in the open sea and possess a tadpole-like body structure consisting of a trunk and a tail. This physical form closely resembles the free-swimming larval stage of a sea squirt, which is a related organism from the class Ascidiacea.12
Both the larvacean and the sea squirt larva exhibit characteristic chordate features, including a muscular tail, a notochord, and a dorsal nerve cord. While these features are temporary in sea squirts—being resorbed when the larva metamorphoses into a sessile adult—larvaceans retain this tadpole-like, chordate-bearing morphology throughout their lives.123