[Campbell Biology P.732] A newly discovered invertebrate animal possesses bilateral symmetry... | Practice Question
A newly discovered invertebrate animal possesses bilateral symmetry, three germ layers, and during its development, it forms a larval stage with an apical tuft of cilia and a complete digestive tract that includes both a mouth and an anus. Based on the provided information, into which major clade of bilaterian animals would this organism most likely be classified?
Explanation
The description of the larval stage—possessing an apical tuft of cilia and a complete digestive tract with mouth and anus—perfectly matches the characteristics of a trochophore larva, as depicted and described for Lophotrochozoans in Figure 32.12 b and the accompanying text. This, combined with bilateral symmetry and three germ layers defining bilaterians , strongly indicates classification within the Lophotrochozoa clade.