What is the X in X-mas?
Any of various, mostly small worms of the phylum Acanthocephala that live parasitically in arthropods as juveniles and in the intestines of vertebrates (especially fish) as adults. Acanthocephalans have a cylindrical, retractile proboscis that has rows of hooked spines and is used for attachment to a host. Also called spiny-headed worm.
any animal of the invertebrate phylum Acanthocephala. A proboscis, or snout, which bears hooks, gives the group its name. There are about 600 recorded species, all of which are parasites in vertebrates (usually fish) as adults and in arthropods as juveniles. The adults are usually less than 1 cm (0.4 inch) in length, but some reach 50 cm (about 20 inches) or more. Spiny-headed worms are found throughout the world