Ascaris has a pseudocoelom, making (A) the correct answer.

A pseudocoelom is a fluid-filled body cavity derived from the embryonic blastocoel, not fully lined by mesoderm—unlike a true coelom. It lies between the mesoderm-lined body wall and endoderm-lined gut, acting as a hydrostatic skeleton and nutrient distributor in nematodes like Ascaris.

Option Analysis

(A) Ascaris

Ascaris (phylum Nematoda, roundworm) possesses a classic pseudocoelom, which fills ~40% of its body volume, supports longitudinal muscles, and enables burrowing via hydrostatic pressure.

(B) Fasciola

Fasciola (liver fluke, phylum Platyhelminthes) is acoelomate, lacking any body cavity—its organs are packed in solid parenchyma between ectoderm and endoderm.

(C) Beroe

Beroe (ctenophore, comb jelly) has a true coelom, with a complete mesodermal peritoneum lining its branched canal system for digestion and circulation.

(D) Sea anemone

Sea anemone (phylum Cnidaria) is acoelomate, featuring a gastrovascular cavity (enteron) as its sole internal space, without mesoderm or coelomic structures.

The animal that has a pseudocoel is Ascaris, a nematode exemplifying pseudocoelomates—organisms with a persistent blastocoel serving as a body cavity. This evolutionary intermediate between acoelomates and eucoelomates aids hydrostatic locomotion and organ suspension, key for exams like NEET.

Pseudocoelom Characteristics

Pseudocoeloms lack full mesodermal lining, allowing direct endoderm-gut contact while mesoderm sheathes the body wall. Fluid pressure enables flexibility without segmentation. Nematodes dominate this group (~25,000 species).

Body Cavity Comparison

Exam Relevance

Which animal has a pseudocoel tests coelom evolution: acoelomates (flatworms, cnidarians) → pseudocoelomates (nematodes, rotifers) → coelomates (annelids+). Ascaris’ pseudocoel links to its parasitic lifestyle and eutely.