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The Acanthocephala (Greek akanthos, thorn + kephale, head) are a group of parasitic worms. They may be called known as acanthocephales, thorny-headed worms, or spiny-headed worms. They have an evertable proboscis, armed with spines, which they use to pierce and hold the gut wall of the host. Acanthocephalans have complex life cycles, with a number of hosts, including invertebrates, fishes, amphibians, birds, and mammals. About 1150 species have been described.
The Acanthocephala were thought to be a separate phylum. Recent genome analysis has shown that they are closely related to rotifers. Since all parasites are derived from free-living forms, the Acanthocephalans are modified rotifers.[1] This is an example of molecular phylogenetics. In due course, spiny-headed worms will probably be placed in a taxonomic rank below phylum, such as sub-phylum or class.[2]
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