Question

The correct classification of Balanoglossus Is
A. Chordata → Vertebrata → Enteropneusta
B. Chordata → Vertebrata → Pterobranchia
C. Chordata → Hemichordata → Pterobranchia
D. Chordata → Hemichordata → Enteropneusta

Answer 1

Hint: Balanoglossus is an evolutionary link between vertebrates and invertebrates. It belongs to hemichordata subphylum.

Complete Answer:
- Balanoglossus is a burrowing, aquatic animal exclusively. It lies between tide markers on the coasts of warm and temperate oceans in shallow waters. The distribution of Balanoglossus is global.
- Balanoglossus is a tubicolous living in the sandy bottom with U-shaped burrows. Mucus, secreted by the mucous gland, is lined to the walls of the tube. The body is soft, lengthy and cylindrical with a huge amount of mucus covered and ciliated all over the Balanoglossus.
- The animal's length ranges between 2 cm and 2.50 m. The main types are drab colour while reddish tints are also present; some species are luminescent because of mucus. The odor is offensive. The body is bilaterally symmetrical and separated into three regions, i.e. proboscis or protostome, collar or mesosome, trunk or metasome.
- The Balanoglossus belongs to the sub phylum Hemichordata under the phylum chordata. They belong to the class Enteropneusta.

Thus, the correct answer is option D. i.e., Chordata → Hemichordata → Enteropneusta.

Note: Balanoglossus is an acorn worm and evolutionary link of invertebrates and vertebrates as a hemichordata. Balanoglossus is a deuterostome, which is similar to Ascidian or marine squirts in that it has branch openings or gill slits. In the upper part of the body it has notochord and has no chord of its nerve. However, it has a stomochord within the collar that is a gut chord. Their heads can be just 2.5 mm to 5 mm large.