An Unusual Type of Neoechinorhynchus cylindratus (Acanthocephala: Neoechinorhynchidae) from Gambusia affinis in Peru, with Notes on Introductions

Background: Neoechinorhynchus cylindratus Van Cleave (Zoo Anz 43: 177–1990, 1913) Van Cleave (Ill Natl Hist Surv Bull 13:225–257, 1919) is a North American acanthocephalan originally described from Micropterus salmoides (Lacépède) in Pelican Lake, Minnesota. It is common in Centrarchids but also not infrequent in fishes of other families. Purpose: A unique population of N. cylindratus was discovered in Peru. It needed to be described and its introduction into Peru investigated. Methods: Standard processing of specimens and staining in Borax carmine and fast green for creating whole mounts were employed. Literature sources were available from the OMA personal collection. Results: The descriptive accounts of N. cylindratus have been rather stable over the years since its original description. It has been, however, oddly identified from Gambusia affinis (Baird and Girard) in Peru. Females of the Peruvian specimens were, however, not typical in having a terminal-near terminal gonopore at odds with the sub-ventral position characteristic of the usual populations of N. cylindratus in North America. We describe the Peruvian material and outline the distinct morphological variations from the North American populations in the position of the female gonopore, among other characters. We also explain its introduction into Peru and the translocation of the position of female gonopore to the terminal position. Conclusions: The translocation to the terminal position of the female gonopore in the Peruvian material is attributed to host related developmental factors. The route of introduction of N. cylindratus into Peru through the introduction of G. affinis from the United States has been accounted for. It may be comparable to the introduction of the same acanthocephalan species into northern Mexico via the documented introduction of its primary host, M. salmoides, also from the United States into Mexico in 1930. The introduction of Acanthocephalus dirus Van Cleave (Ill Natl Hist Surv Bull 13:225–257, 1919) (Van Cleave and Townsend, 1936) into Mexico is also discussed.