Acanthocephalans

Adult acanthocephalans infect the small intestines of vertebrate animals. Acanthocephalans are most often misidentified as tapeworms in situ because they are white, flattened, wrinkled, and contain a thorny-proboscis.

Prosthorhynchus ​sp.
A closer view of the anterior end of Prosthorhynchus, an Acanthocephalan of birds, reveals numerous spines on an un-retractable proboscis. These spines are common across the order with numbers differing between species. Macracanthorhynchus hirudinaceus is known to have six transverse rows of six hooks each.

Macracanthorhynchus sp.
Eggs of Macracanthorhynchus sp. are are 67-110 by 40-65 µm, dark brown in color, pitted, and contain an acanthor (embryo) surrounded by several membranes. The acanthor contains hooks that are not always easily observed.

Macracanthorhynchus ingens
Egg of Macracanthorhynchus ingens recovered from a maned wolf. Definitive hosts of Macracanthorhynchus ingens include raccoons, wild canids, and domestic dogs. Beetles and millipedes serve as intermediate hosts, and paratenic hosts include frogs and snakes.

Proboscis of Macracanthorhynchus hirudinaceus, the giant thorny-headed worm of pigs. Clinical disease is caused, in part, by mechanical damage associated with insertion of the armed proboscis into the intestinal mucosa.

Adult female Macracanthorhynchus hirudinaceus, the giant thorny-headed worm of pigs, are 20 – 65cm long. The proboscis is evident at the anterior end on both adults in this image