The thorny-headed worms are scientifically classified as which group?

• A. Cestodes
• B. Trematodes
• C. Acanthocephalids
• D. Nematodes

Answer: (C)

Thorny-headed worms belong to their own phylum, Acanthocephala (Acanthocephalids). They are endoparasites with a distinctive, retractable, spiny proboscis that they use to anchor themselves to the intestinal wall of their vertebrate hosts. This feature sets them apart from other parasitic groups. They also differ from flatworms like cestodes (tapeworms) and trematodes (flukes) because acanthocephalans are not segmented and many adults lack a true digestive tract, absorbing nutrients across their body surface. Their life cycles typically involve an arthropod intermediate host before reaching the final vertebrate host, adding to their unique biology. In contrast, nematodes are roundworms with a separate digestive system and a different body plan altogether. All these distinctions help identify thorny-headed worms as Acanthocephalids.