platyhelminth

All of them are invertebrates. They all have long, narrow bodies without legs. All worms also have tissues, organs, and organ systems. Worms have bilateral symmetry.

Wuchereria is a parasitic roundworm belonging to phylum Aschelminthes. Schistosoma is a parasitic flatworm belonging to phylum Platyhelminthes. Thus, the correct answer is option B.

The phylum name Platyhelminthes literally means “flatworms.” Members of this phylum are soft, thin-bodied, leaf or ribbonlike worms, including the familiar planaria of ponds and streams, as well as the flukes and tapeworms parasitic in human and other animal bodies.

The parasitic flatworms include flukes (classes Monogenea and Trematoda) and tapeworms (class Cestoda). There are more than 4,000 species of Monogenea, 9,000 of Trematoda and 5,000 of Cestoda.

The phylum platyhelminthes includes the organism like flatworms, earth worm and many other species. They play a major role in the marine, terrestrial and freshwater ecosystem. They help the farmers by increasing the fertility of the soil which overall increases the economical importance of the soil and earthworms.

Platyhelminthes have the following important characteristics:

• They are triploblastic, acoelomate, and bilaterally symmetrical.
• They may be free-living or parasites.
• The body has a soft covering with or without cilia.
• Their body is dorsoventrally flattened without any segments and appears like a leaf.

Flatworms possess an elaborate muscle system consisting of longitudinal, circular, and oblique fibers. Small free-living species primarily use their epidermal cilia for locomotion, assisted by muscular contractions in larger forms.

hydrostatic skeleton

Planarians are considered to be among the most primitive animals which developed the central nervous system (CNS).