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Body is distinguished into proboscis, collar, and trunk in
A. Herdmania
B. Amphioxus
C. Petromyzon
D. None of the above

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Last updated date: 13th Jun 2024
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Answer
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Hint: Phylum Chordata includes the group of animals that have notochord. It may be seen either throughout their life or only in the embryonic period of life. Phylum Chordata is divided into four subphyla. They are Hemichordata, Urochordata, Cephalochordata, and Vertebrata.

Complete answer:
Hemichordata is a subphylum that comes under the phylum Chordata. It is also called stomochordata. Hemichordates do not have a true notochord. They have gill slits in their body. These are closely related to the phylum Echinodermata. Because of this, they are also considered as a separate phylum. Hemichordates are mostly worm-like organisms. They have a body cavity or coelom in their body. The body is distinguished into three parts. They are proboscis, collar, and trunk. Balanoglossus (Acorn worm or tongue worm), Glossobalanus, etc are examples. These animals are mostly marine and they burrow in sand or soft mud. Urochordata is a subphylum of the phylum Chordata. They are also known as tunicata. The notochord is present only in the larval tail of these animals. The bodies of these animals are covered with tunicine, which is made up of cellulose. Herdmania, Ascidia, Ciona, Salpa, Doliolum, etc are examples of tunicates. In Cephalochordata, the notochord is present from the head to the tail. Branchiostoma (amphioxus) is a cephalochordate that is also known as sea lancet. Hemichordata, Urochordata, and Cephalochordata are together called Protochordates or Prochordates. Petromyzon, which is also known as sea lamprey, belongs to the class Cyclostomata. These vertebrates have a notochord present in the embryonic period which is later replaced by a vertebral column in adults.
Hence, the correct Option is D.

Note: In urochordates, animals have notochord only in their larval stage. They are absent in the adult stage and it is seen in larvae of Ascidia. This phenomenon in which an organism loses its advanced features like notochord during metamorphosis is called retrogressive metamorphosis.