Question

Which phyla has most parasite animals?

Answer 1

Apicomplexa or Apicomplexia is a large phylum of parasitic protists including human pathogens such as the Plasmodium and the Toxoplasma as well as many other parasites, which are nonpathogenic to human beings, but affect a wide variety of animals.  

All apicomplexans are parasitic and lack contractile vacuoles and locomotor processes.

Answer 2

The Nematoda is one of the largest invertebrate phyla. It includes marine, freshwater, terrestrial and parasitic species. Nematodes also occur in high abundance in most habitats.