Invertebrate Chordates Section 31.2

Chordate Characteristics Endoskeleton is completely internal Notochord develops along the back of the embryo Notochord becomes the backbone in vertebrates A hollow, dorsal nerve cord runs the length of the body Pharyngeal pouches develop & become gills, glands, or the inner ear A postanal tail that extends beyond the anus

Invertebrate Chordates These are 2 small groups of chordates (have a notochord) that are invertebrates (without a backbone) Urochordata – tunicates Cephalochordata - lancelets

Tunicates Only larvae have the chordate features (notochord, nerve cord, postanal tail) – adults lack them Adults do keep the pharyngeal pouches Sessile Marine Filter-feeding All are hermaphrodites

Tunicates

Tunicates: also called ‘sea squirts’

Lancelets Fossils are much older than any fish species Only a few centimeters long V-shaped bundles of muscles arranged in segments Live in shallow ocean water, with tails buried and heads exposed Filter plankton out of the water Sexes are separate

Lancelets have transparent skin