Which describes adult sea squirts? A. They are bilaterally...

Which describes adult sea squirts?
A. They are bilaterally symmetrical.
B. They have the same adult features as lancelets.
C. As adults, they have only one chordate feature.
D. They are actively swimming predators.

Key Concepts

Retention of Chordate Features in Adults

In adult sea squirts, only one chordate feature, such as the pharyngeal slits, is maintained. This reduction in chordate features is significant in understanding the evolution and developmental biology of tunicates, highlighting how drastic morphological changes can occur between life stages in some chordate groups.

Metamorphosis in Sea Squirts

Sea squirts demonstrate a process of metamorphosis where they transition from a free-swimming larval stage, which exhibits the complete set of chordate features, to a sessile adult form. This dramatic transformation involves the reduction or loss of many of the ancestral chordate characteristics, resulting in an adult that retains only select chordate traits.

Chordate Characteristics

Chordates are defined by a set of anatomical features that include a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. In many chordates, these features are present at some stage of development, providing a basis for understanding evolutionary relationships among various organisms.

Tunicates

Tunicates, which include sea squirts, are a subgroup within the chordates. Although the larval forms of tunicates display typical chordate characteristics, including bilateral symmetry and a notochord, adult tunicates undergo significant morphological changes, often losing many of these features, which makes them unique among chordates.

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