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In summary, the notochord plays essential roles in embryonic development. The notochord provides a directional reference to the surrounding tissue as a midline structure during embryonic development, acts as a precursor for vertebrae and a primitive axial endoskeleton. In aquatic animals it can facilitate tail motion when swimming. [1]
The lancelet is a small, translucent, fish-like animal that is one of the closest living invertebrate relatives of the vertebrates. [ 80 ] [ 81 ] The lancelets were traditionally seen as the sister lineage to the vertebrates ; in turn, these two groups together (sometimes called Notochordata) were considered the sister group to the Tunicata ...
A tunicate is an exclusively marine invertebrate animal, a member of the subphylum Tunicata (/ ˌ tj uː n ɪ ˈ k eɪ t ə / TEW-nih-KAY-tə).This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates).
The gut runs just below the notochord from the mouth to the anus, in front of the tail. There is a flap-like, vertical fin surrounding the pointed tail. Gas exchange takes place as water passes through gill slits in the mid region, and segmented gonads lie just behind these. The animal is pearly white and semi-transparent which enables the ...
Woods Hole Oceanographic Institute describes sea squirts as, “Sea squirts belong to the phylum Chordata, which includes all animals with a spinal cord, a supporting notochord (backbone), and ...
[1] [3] The notochord runs down the animal's back with a smooth layer of connective tissue on the exterior, lining an interior core of cells that are loosely packed and contain fluid-filled spaces. [1] The outer sheath resists changes in fluid pressure in the notochord, allowing for flexibility while simultaneously withstanding contraction.
The dorsal nerve cord is an anatomical feature found in chordate animals, mainly in the subphyla Vertebrata and Cephalochordata, as well as in some hemichordates.It is one of the five embryonic features unique to all chordates, the other four being a notochord, a post-anal tail, an endostyle, and pharyngeal slits.
As a general rule, the larva possesses a long tail, containing muscles, a hollow dorsal nerve tube and a notochord, both features clearly indicative of the animal's chordate affinities. One group though, the molgulid ascidians, have evolved tailless species on at least four separate occasions, and even direct development. [8]