Question

What is true about Nereis, scorpion, cockroach and silverfish?
A) They all possess dorsal heart
B) None of them is aquatic
C) They all belong to the same phylum
D) They all have jointed paired appendages

Answer 1

They are usually cylindrical, not only present in sandy regions, but also adapted for burrowing. Sometimes they stick on rocks to seagrass or other grass and occasionally they group in large numbers.

Complete Answer:
In the family Nereididae, Nereis is often a genus of polychaete worms. For locomotion, Nereis exhibits setae and parapodia. They could have two kinds of setae found on the parapodium. Acicular setae provide protection. Locomotor chaetae are the bristles visible on the outside of the Polychaeta, which are for crawling.

Now, let us find the solution from the options-
- Many of these invertebrates have a dorsal heart in their anatomy, a long elongated tunnel located in the centre of the thorax’s dorsal line.
- Nereis contains several animals, most of which are marine species. Thus, option B is not the correct option.
- The phylum arthropoda relates to the same silverfish, scorpions, and cockroach; however Nereis is also an annelid. Thus, option C is not the correct option.
- All Phylum arthropod insects possess jointed appendages, and yet Nereis does not have. Thus option D is not the correct option.

Thus, the correct answer is option (A) They all possess a dorsal heart.

Note: Nereis is an osmo-conformer. Nereis is dioecious, releasing their haploid gametes into the form of water, a system called spawning. Nereids also develop a larval stage that is close to that of molluscs, i.e. a trochophore larva, upon fertilisation and mitotic partitions of the zygote.