Question

Pygidium in Nereis represents
A Prostomium
B Anal segment
C Peristomium
D Head

Answer 1

Hint Nereis is a polychaete worm genus in the Nereididae family. It contains a large number of species, the most of which are marine. For locomotion, Nereis has setae and parapodia. They may have two different forms of setae on their parapodia. Support is provided by acicular setae.

Complete answer:
The pygidium is the shield that crustaceans and other arthropods, such as insects and extinct trilobites, have on their backs. It contains the anus and, in females, the ovipositor in groups other than insects.
Prostomium: The prostomium is the cephalized first body segment in the anterior end of an annelid worm's body. It is usually a tiny shelf- or lip-like protrusion over the dorsal side of the mouth and is located in front of the mouth
Anal Segment: The terminal segment is known as the anal segment or pygidium, and it has a small round orifice at its posterior end known as the anus. A pair of extended anal cirri are found on the anal segment. A nephridial aperture can be found near the base of the parapodium on the ventral surface.
Peristomium: In the anterior end of an annelid worm's body, the periosteum is the second body segment. It is located right behind the prostomium and houses the mouth, tentacular cirri, and feeding palps, which can also be found on the prostomium.
Head: Rag worms and clam worms are typical names for Nereis worms. The body is long, slim, and flattened dorso-ventrally, measuring 5-30 cm in length. The head is divided into two sections: the prostomium, a roughly triangular anterior lobe, and the peristomium, a ring-like posterior component.

So, we can see that pygidium is present on anal segment.

Note: Nereis is a polychaete genus that lives in sand or mud burrows, sometimes with clams, which is why its species are known as clamworms or sandworms. The body is long, slim, and flattened dorso-ventrally, measuring 5-30 cm in length.