On the immature stages of Pallisentis (Pallisentis) celatus (Acanthocephala: Quadrigyridae) from occasional fish hosts in Vietnam

Immature stages of Pallisentis (Pallisentis) celatus Van Cleave, 1928, were collected from the intestine of three species of occasional fish hosts in the Red River near Hanoi (21°1'N; 105°52'E). These are new records from Clarias fuscus (Valenciennes in Cuvier & Valenciennes, 1840), Ophiocephalus maculatus (Lacépède, 1801) and Mastacembelus armatus (Lacépède. 1800). Worms reached moderate size hut did not reach sexual maturity or develop eggs and sperm. Measurements and illustrations are compared with those of sexually mature adults from China and Vietnam as previously reported by other observers. Attachment structures (hooks and spines) reached their (previously measured) maximum size compared to other anatomical structures in the youngest worms. Information on certain diagnostic features, e.g., giant nuclei, not recorded for the original and subsequent descriptions, are provided in this study. An additional pathway in the life cycle of P. (P.) celatus involving occasional fish hosts is proposed. © National University of Singapore.