The scorpion, the cockroach, the silverfish and the Nereis are all different from each other. While the scorpion and the cockroach are mainly terrestrial creatures, the nereis is an aquatic animal. All of these animals have dorsal heart. It is a long, tube-like structure that is located in the mid dorsal line of the thorax.
The Nereis is a class polychaeta of the phylum Annelida. This annelid does not have jointed limbs. They live in burrows in sand. Their excretory system includes segmentally arranged tubules called nephridia. Most annelids are monoecious. However, there are some species that are hermaphrodite. These animals have a dorsal heart but do not have pharyngeal gills-slits.
The silverfish is a member of the Phylum Arthopoda. It feeds on starch and is therefore an arthropod. Similarly, the cockroach is a member of Phylum Arthopoda, but it is also a terrestrial animal. Both cockroach and silverfish have joined appendages.
If you are interested in learning more about the scorpion, the cockroach, the Nereis, and the silverfish, you can go to EduRev.com and take a practice test to find out what is true about these creatures. You can also read about their characteristics, their habitats, and more. And you can see their pictures as well. After you learn everything you need, you can make a wise decision on whether or not you want to keep them. So get ready to have fun with these fascinating animals! Good luck!