Passerine Birds as Experimental Hosts for Posthodiplostomum minimum (Trematoda: Diplostomidae)

Abstract

Posthodiplostomum minimum (MacCallum, 1921) Dubois, 1936, is a common strigeoid trematode parasitizing several species of herons. Metacercariae of this species, formerly known as Neascus van cleavei (Agersborg), occur in a wide variety of fresh-water fishes, where they invade the liver, spleen, opisthonephroi, mesenteries, and pericardium. Numerous life history studies on this species have been published, including those by Ferguson (1936, 1938, 1940, 1943), Hunter and Hunter (1940), J. H. Miller (1954), and Hoffman (1958). Several attempts to employ birds other than herons as experimental hosts for P. minimum have been reported. Ferguson (1936, 1938) and J. H. Miller (1954) showed that newly hatched, unfed chicks serve as suitable definitive hosts. Pigeons and ducklings, however, as well as chicks older than 4 days or those having been fed prior to exposure to metacercariae, remained refractory to infection, according to the latter investigator. Adults of the 14 known species of Posthodiplostomum, according to Dubois (1957), demonstrate a marked specificity for birds of the Order Ciconiiformes, particularly herons (Family Ardeidae). Dubois believes that the selective mechanisms responsible for such specificity T among avian strigeoids are related to chemical factors associated with the activity of the tribocytic organ (holdfast). That host specificity among certain avian diplostomid flukes may be somewhat less rigid than Dubois maintains was demonstrated by a series of experiments involving metacercariae of P. minimum. A preliminary report of these studies (conducted during the summers of 1959 and 1960) at the Iowa Lakeside Laboratory at Lake Okoboji) was published in 1960.