Neoandracantha peruensis n. gen. n. sp. (Acanthocephala, Polymorphidae) described from cystacanths infecting the ghost crab Ocypode gaudichaudii on the Peruvian coast.

The cystacanths of Neoandracantha peruensis n. gen. n. sp. are described from the ghost crab Ocypode gaudichaudii collected from the Pacific coast of Peru. While it is uncommon to describe acanthocephalan taxa from immature stages, the presence of clear-cut distinguishing features separating the present material from its nearest congeneric taxa, and the absence of adults, justifies the erection N. peruensis. The new genus is distinguished by having three separate fields of trunk spines. Specimens of N. peruensis have a slender trunk with two anterior swellings, 3 separate fields of spines on the foretrunk swelling, and no genital spines on the hindtrunk. The proboscis of the new species is heavily armored with 21-22 longitudinal rows of 22 hooks each. Hook no. 14 is more robust ventrally than dorsally. Cystacanths of N. peruensis also have a long tubular hindtrunk and the males have diagonal testes in the midtrunk swelling. Specimens of the closely related Andracantha Schmidt, 1975 have anteriorly enlarged pear-shaped Corynosoma-like trunks, only two fields of anterior trunk spines with occasional genital spines, and bilateral or tandem testes. Proboscides of species of Andracantha have considerably fewer hooks that gradually decrease in size posteriorly. The taxonomic component of this work is amplified by metal analysis of hooks and spines that shows a marked amount of magnesium (Mg) in hooks but not in spines. The highest level of sulfur (S) was found in the outer layer of hooks and anterior spines. The metal footprint of hooks and spines varies in different species of acanthocephalans and has an interspecific diagnostic value.