A phylum of bilaterally symmetrical, pseudocoelomate, worm-like organisms most of which do not have an excretory system; all lack a gut. A re-tractable proboscis is present, covered with the recurved spines that give the animals their common name. All acantho-cephalans are endoparasitic, living in two or three marine or terrestrial vertebrates during their development. There are about 600 species.
Subjects: Ecology and Conservation — Zoology and Animal Sciences.