Question

The jawless vertebrate is
A. Crocodile
B. Loris
C. Hyla
D. Fox
E. Petromyzon

Answer 1

Hint: An agnathan that resembles an eel is known as a jawless vertebrate. They are commonly known as sea lampreys. It has a sucker-like mouth that helps in the filter-feeding. It is an example of a parasitic species.

Complete answer: Petromyzon marinus or sea lampreys are a parasitic lamprey that is native to the Atlantic coast of North America and Europe, in the western Mediterranean Sea, and in the great lakes. It is black, brown, or gray on the back and gray and white on the underside. They feed on a variety of fishes. They have a suction-cup like a mouth that helps in attaching to the skin of prey. They have an elongated eel-like body that is divided into head, trunk, and tail. They have soft and smooth skin that contains unicellular mucous glands. They do not have scales. They lack jaws and retain a notochord for their whole life. Their vertebral column has cartilage that surrounds the notochord. They have bilateral symmetry. During their larval phase, they feed on algae and small organisms. In the parasitic phase, they feed on various fishes. While in their spawning phase, they don’t eat.
Hence, the correct option is (E)-Petromyzon.

Note: Sea lampreys have a distinctive eel-like body that is easily identified by the wide oral sucker that is filled with many small teeth arranged in circular rows. It is also known as a jawless vertebrate. Other organisms such as crocodile, loris, Hyla, and fox belong to gnathostomes or jawed vertebrates.