Acanthocephala is a group of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host. Acanthocephalans have complex life cycles, involving at least two hosts, which may include invertebrates, fish, amphibians, birds, and mammals. About 1420 species have been described.
Acanthocephala
Some key features of acanthocephalan morphology
A diagram of the life cycle of Polymorphus spp.
Adult Pomphorhynchus in a bluefish
Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schistosomes reside in blood vessels.
Hookworms attached to the intestinal mucosa
Two pinworms
Processed helminth eggs samples from a dry toilet in Kenya
Analysing for helminth eggs in samples of feces from a dry toilet in Kenya