In this article we will discuss about the structure of King Crab (Limulus) with the help of a diagram.
1. It is commonly known as king-crab and is a marine arthropod found burrowing in sand along Atlantic coast.
2. Body is comprised of an anterior cephalothorax or prosoma and a posterior- opisthosoma.
3. Cephalothorax (prosoma) is broad, convex above and concave below and bears a pair of median and a pair of lateral eyes and three longitudinal ridges above.
4. It also bears six pairs of non-locomotor limbs below around the mouth. All the legs, except the last pair, are chelate.
5. The opisthosoma is divided into mesosoma, metasoma and telson and is movably articulated with prosoma (cephalothorax).
6. The mesosoma is hexagonal, broad, comprises of six segments and bear 6 pairs of flattened and plate-like appendages.
7. The first pair of appendage is united to form a genital operculum, whereas the remaining five pairs bear book-gills or book-lungs for respiration on their exopodites.
8. The metasoma is small, unsegemented and vestigial and lies behind the mesosoma and in front of a long and tapering telson.
9. Malpighian tubules absent and excretion through coxal glands.
10. It is regarded as a living fossil and feeds on worms and bivalved molluscs.
11. Development through trilobite larva.