Arthropod-intermediate-host
Guides
Acanthocephala
thorny-headed worms, spiny-headed worms, acanthocephalans
Acanthocephala is a phylum of obligate endoparasitic worms known as thorny-headed or spiny-headed worms, characterized by an eversible proboscis armed with recurved hooks used to attach to host intestinal walls. They lack a mouth and digestive system, absorbing nutrients directly through their tegument. The phylum contains approximately 1,200–1,420 described species with complex life cycles involving arthropod intermediate hosts and vertebrate definitive hosts. Recent molecular evidence indicates they are highly modified rotifers, now sometimes classified within Syndermata or Rotifera.