Question

Body cavity present in Arthropods and Molluscs is known as……………..

Answer 1

Hint: Within many invertebrates, including arthropods and molluscs, the haemocoel body cavity, which is an extension of part of the blood supply. The haemocoel never opens to the outside, in comparison to the COELOM, nor does it contain germ cells.

Complete answer:
Haemocoel is the blood-filled body cavity of arthropods and molluscs (e.g., cockroaches and pilas). The haemocoel is an expanded blastocoel that decreases the coelom considerably (this is confined to the gonad and excretory organ cavities). It behaves like a hydrostatic skeleton.
A large perivisceral coelom is found like that of an earthworm in the embryonic stage of the cockroach. But the blood vessels enlarge and swell into irregular spaces as the development continues, and eventually, the perivisceral coelom is completely obliterated and replaced by certain irregular spaces called sinuses or lacunae. The sinuses come together to form a blood-filled body cavity in which all the visceral organs lie. The body cavity itself is also part of the circulatory system and is also referred to as the haemocoel (haema = blood + coel = cavity), i.e., the cavity filled with blood. The haemocoel stretches from the anterior end of the body to the posterior end of a cockroach. In fact, the haemocoel lacks the epithelium of a true coelom and is split by two horizontal septa into three larger sinuses. Muscular membranous structures are the septa; one dorsal and the other ventral diaphragm are the dorsal diaphragm.

Additional information:
In the family Ampullariidae, the apple snail, Pila is a genus of large freshwater snails with an operculum, African and Asian apple snails, aquatic gastropod mollusks.
Insects do not have blood vessel structures like those in mammals. Instead, insects have a cavity full of blood from insects (called hemolymph) and insect organs are suspended in this cavity. This suggests that when the blood 'washes' across the organs, the organs do not have a particular blood supply but are suspended in the blood and obtain nutrients.

So, the correct answer is ‘Haemocoel’.

Note:
Within the phylum Mollusca, the gastropods, generally known as snails and slugs, belong to a broad taxonomic class of invertebrates called Gastropoda. Snails and slugs from saltwater, freshwater, and land compose this class. As well as freshwater snails, freshwater limpets, and ground snails and slugs, several thousands of species of sea snails and slugs occur.