Invasion of vertebrate lungs by the polystomatid monogeneans Pseudodiplorchis americanus and Neodiplorchis scaphiopodis

Abstract

SUMMARYSome unique features of monogenean biology have emerged from studies on 2 polystomatids which infect spadefoot toads in Arizona, USA: Pseudodiplorchis americanus in Scaphiopus couchii and Neodiplorchis scaphiopodis in S. multiplicatus and S. bombifrons. Transmission is confined to 1–3 nights each summer when the desert-adapted toads enter water to spawn. Encapsulated larvae complete development in utero and hatch within seconds of deposition; their body length (up to 600 μm) is 2–4 times greater than that of most other oncomiracidia, and their swimming life (over 48 h at 25–27 °C) is twice that usual amongst monogeneans. The ciliated oncomiracidia invade the nostrils, a target usually above the water surface and requiring migration over the exposed skin; remarkably they tolerate drying for up to 1 h (at 32 °C, 45% rel. hum.). The larvae migrate via the buccal cavity and glottis to the lungs where juvenile development occurs until early autumn. Migration from the lungs to the urinary bladder (by an as yet undetermined route) is followed by maturation and reproduction during host hibernation, and developing embryos accumulate in preparation for a period of transmission more restricted than that of any other monogenean. No other monogenean is known to exploit the lungs nor to inhabit, successively, anterior and posterior sites of the same adult host individual.

Life history specializations of monogenean flatworms: A review of experimental and microscopical studies

“…The host of Pseudodiplorchis americanus, Scaphiopus couchii, collected in the San Simon valley, southeast Arizona, was maintained as described by Tinsley and Earle (1983).…”

“…Pseudodiplorchis americanus (see Fig. 3), a parasite of the North American spadefoot toad, Scaphiopus couchii, is unique for its adaptations to a desert environment, and for the complexity of its internal migrations following infection (Cable and Tinsley, 1992a;Tinsley and Earle, 1983;Tinsley and Jackson, 1986). Parasite eggs, laid during brief (less than 7 hour) periods when the toads enter water to spawn, hatch immediately.…”

Biologie des populations des Monogènes Polystomatidae

“…(TINSLEY & OWEN, 1975). The initial development of Pseudodiplorchis and Neodiplorchis occurs in the host's lungs and there may be heavy burdens of blood-feeding larvae (TINSLEY & EARLE, 1983). However, since each year's invasions are more or less synchronized, the duration of this potentially-damaging phase in the life cycle is limited, and no instances of host mortality associated with heavy lung infections have been recorded during extensivef ield and laboratory studies (Tl NSLEY, unpublished).…”

Stimuli de l'environnement, organes des sens et comportement des Monogènes juvéniles et adultes

“…The utérus of the adult parasite in the bladder of its host is aiready packed with fully-developed, thin-shelled eggs, when, at the advent of the annual rains, the toads émerge from dormancy in deep burrows in the sand (TINSLEY and EARLE, 1983). The toads have 1-3 days in which to mate and spawn in temporary rain pools.…”