Question

Limulus belongs to group
A) Insecta
B) Crustacea
C) Merostomata
D) Onychophora

Answer 1

Hint: Limulus is known as king crab. Limulus has remained unchanged for 190 million years. Therefore, it is also called a "living fossil". Excretion takes place through coxal glands which are four in number. Respiratory organs are book gills. Limulus belongs to the largest phylum of the animal kingdom.

Complete answer:
The members of Arthropoda are metamerically segmented bilateral symmetrical multicellular animals. Their metamers are not similar, but they are specialized and usually have a fixed number. All segments are paired. At least a couple of appendages act like jaws.
Depending on the division of the body and the presence or absence of certain attachments, species of phylum Arthropoda are divided into various classes.
A) The body is divided into head, abdomen, and thorax. It bears a pair of compound eyes and a pair of antennae. The chest consists of 3 segments with 3 pairs of legs and usually 2 pairs of wings. Uric acid is the main waste product. Examples: cockroaches, bedbugs, grasshoppers, termites, butterflies, beetles, wasps, aphids, silkworms, etc.
B) Crustacea: the body is divided into the cephalothorax (head, chest) and abdomen. On the back, the ribcage of the head is covered with a thick shell of the exoskeleton. There are two pairs of antennae and a complex pair of rod eyes. Examples: Palinurus Lobster, Crab, Lucifer, Eupagarus, Lepus, Balanus, etc.
C) Merostomata-On the sides there are marine forms with rather developed complex eyes. The head and thorax are combined to form a single unit cephalothorax, covered with a single sheet of an exoskeleton. The first usual pair of limbs are chelicerae, followed by 5 pairs of limbs - walking legs. The protruding coccyx, called the tail joint, sits at the end of the body and acts as a lever to push and balance as it moves. Respiratory organs - gills (paper gills), which are located in the lamellar processes of the mesosomes. Adults crawl from floor to belly, but young people can actively swim. Example - Limulus
D) Onychophora-Platypus belongs to class Onychophora.

Hence from the points, it’s clear that the correct option is (C).

Note: The body of the Limulus consists of the anterior torso and the posterior opisthosoma. Removal of waste is through coxal or brick-red glands. The prosoma is wide, convex above, concave below, with a central pair and a pair of lateral ocelli and three longitudinal ribs above. It also bears 6 pairs of fixed limbs around his mouth. All legs are chipped except for the last pair. opisthosoma is divided into mesosomes, metasomes, and telsons and has a flexible connection with prose (cephalothorax). The mesosomes are hexagonal, wide, consisting of 6 nodes, with 6 pairs of flat appendages.