Question

Which of the following animals are the members of Cephalochordata?
A. Rhabdopleura and Amphioxus
B. Branchiostoma and Asymmetron
C. Petromyzon and Myxine
D. Ciona and Appendicularia

Answer 1

Cephalochordata is the group of organisms that belong to the chordate subphylum. The word cephalochordata is derived from a Greek word and it means head chord.

Complete answer:
Cephalochordata belongs to the chordate. They possess segmented elongated bodies, notochord that extends the length of the body, extending from head to tail, persisting throughout the animal's life, dorsal hollow nerve cord, pharyngeal slits, post-anal tail. Let us analyse each given option to find out the correct answer.

Option A: Amphioxus , also called Branchiostoma is a member of the Cephalochordata. They possess segmented elongated bodies, notochord that extends the length of the body, extending from head to tail, persisting throughout the animal's life, dorsal hollow nerve cord, pharyngeal slits, post-anal tail. Rhabdopleura belongs to the phylum Hemichordata. They are a small, marine species of worm-shaped animals.

Option B: Cephalochordata is defined by the presence of a notochord. The notochord remains throughout life. The cephalochordates are marine animals. They have segmented bodies. They possess elongated bodies with a notochord that extends the length of the body. They have cirri surrounding the mouth for obtaining food. Asymmetron (also called Epigonichthyes) and Amphioxus (also called Branchiostoma) are cephalochordates. Both animals belong to the Cephalochordta.

Option C: Petromyzon (Lamprey) and Myxine (Hagfish) belong to class Cyclostomata of division Agnatha of Vertebrata.

Option D: Ciona is a genus of sea squirts. The body of Ciona is bag-like. Ciona is a tunicate, which, like vertebrates, belongs to the chordate phylum. Both Appendicularia and Ciona belong to the phylum chordata.

Hence the correct answer is option B.

Note: It is to be noted that the main difference between Urochordata and Cephalochordata is that Urochordata consists of a notochord extended in the head region whereas Cephalochordata contains the notochord in the posterior region of the body.