The complete life cycle of the trematode Ascocotyle (Phagicola) longa (Digenea: Heterophyidae) is elucidated by natural observation validated by experimental infections. The natural first intermediate host of A. (P.) longa, an agent of human heterophyiasis in Brazil, is the cochliopid snail Heleobia australis (new first intermediate host). Metacercariae were found encysted in the body musculature, heart, stomach, liver, kidney, spleen, gonads and mesentery of mullets Mugil liza. Hamsters Mesocricetus auratus were experimentally infected with metacercariae of A. (P.) longa obtained from the mullets, and the adults recovered were used to infect the snails H. australis. Rediae and cercariae of A. (P.) longa are described for the first time. The ultrastructure of the tegument of A. (P.) longa shows a change in spination pattern from the cercaria with single-pointed spines to the metacercaria and adult with multipointed, brush-shaped spines. The life cycle of A. (P.) longa is related to estuaries and coastal lagoons where the recruitment of mugilid juveniles occurs. The high prevalence (100%) of A. (P.) longa encysted in the mullets examined within the urban area of Rio de Janeiro indicates the potentially great public health impact of the consumption of raw mullets.
Pygidiopsis pindoramensis Travassos, 1928, is redescribed from the holotype and specimens obtained from experimental infections of hamsters with metacercariae of the naturally infected poeciliids Poecilia vivipara and Phalloptychus januarius from Rio de Janeiro, Brazil. Ascocotyle (Phagicola) pindoramensis (Travassos, 1928) n. comb. is proposed, based on the presence of a solid, tapering muscular posterior prolongation of the oral sucker and Ascocotyle (Phagicola) mollienisicola (Sogandares-Bernal and Bridgman, 1960) is synonymized with A. (P.) pindoramensis because of the identical morphology and measurements of adults and metacercariae, similar spectrum of fish intermediate hosts (poeciliids), and the same site of infection of the metacercariae. Trematodes designated as Pygidiopsis pindoramensis, previously reported from Argentina and Mexico, represent another species of Pygidiopsis Looss, 1907, because they possess circumoral spines and their oral sucker is devoid of the posterior muscular prolongation. Data on the surface morphology of metacercariae and adults of A. (P.) pindoramensis are inferred from scanning electron microscopy observations.
Pygidiopsis macrostomum Travassos, 1928, originally described based on a single specimen from Rattus norvegicus (Erxleben) in Brazil, has also been reported from a piscivorous bat, Noctilio leporinus mastivus Ribeiro, in Cuba (Odening 1969, Zdzitowiecki & Rutkowska 1980. We have previously redescribed this species from the holotype and adults obtained from hamsters Mesocricetus auratus Waterhouse experimentally infected with metacercariae from naturally infected guppies Poecilia vivipara Bloch and Schneider taken from Rodrigo de Freitas Lagoon in Rio de Janeiro (RJ), Brazil (Simões et al. 2005). However, other aspects of the life history and biology of this species, especially in relation to the first intermediate host, still need to be elucidated. In this work, the life cycle was completed under laboratory conditions and we provide new host records along with the first descriptions of the redia and cercaria. MATERIALS AND METHODSThe guppies Poe. vivipara, Phalloptychus januarius (Hensel) and Jenynsia multidentata (Jenyns) were collected on the edge of the Rodrigo de Freitas Lagoon, RJ, Brazil (22º57'2"S, 43º11'9"W) and examined for metacercariae. A hydrobiid snail, Heleobia australis (d´Orbigny), was collected in the same lagoon and examined for cercariae. Poe. vivipara and H. australis were reared in the laboratory in filtered lagoon water to provide specimens devoid of infection.Two experimental infections (summer and winter) were performed. For each experiment, one hamster M. auratus was fed with the mesenteries of four naturally infected Poe. vivipara and, on the fourth day postinfection (dpi) each was examined for ovigerous adults of Pyg. macrostomum. Two uninfected stocks of snails (summer and winter) were exposed to infection by placing the eggs of adult Pyg. macrostomum, obtained experimentally from hamsters in their aquaria. Laboratory-reared Poe. vivipara (4 in each experiment for summer and winter) were exposed to cercariae obtained from these experimentally infected H. australis. One hamster for each experiment was fed with the mesenteries of the experimentally infected fish and later examined at four dpi for adults of Pyg. macrostomum.All larval stages and adults were studied live, with or without vital stains. Semi-permanent slides were prepared in glycerine jelly (Moravec 1994) and glycerine/picric acid (Ergens 1969). Other specimens were fixed in 70% alcohol or hot 4% formaldehyde solution, stained with Gomori's trichrome or alcoholic chloridric carmine, cleared in beechwood creosote and mounted in Canada balsam. Illustrations were made with the aid of a drawing attachment on a Leica DM LS2 microscope. Measurements are presented as the range, with the mean in parentheses.For scanning electron microscopy (SEM), specimens were fixed for 1h at rt with 2.5% glutaraldehyde in 0.1 M Na-cacodylate buffer and washed in the same buffer. Specimens were post-fixed for 3 h at rt in a solution of 1% osmium tetroxide in 0.1 M Na-cacodylate buffer, dehydrated in an ascending acetone series, dried by criticalpo...
Pygidiopsis macrostomum Travassos, 1928, a poorly known species originally described from a single specimen from Rattus norvegicus (Erxleben, 1777) in Brazil, is redescribed on the basis of metacercariae from the mesenteries of naturally infected guppies Poecilia vivipara Bloch and Schneider, 1801 (Poeciliidae), and adults obtained from an experimental infection of hamsters. Pygidiopsis macrostomum is characterized by the absence of oral spines, vitellaria extending forward to ventral sucker, uterus reaching pharyngeal level, X-shaped excretory vesicle, and an oral sucker/acetabulum ratio of 1:0.8. The surface ultrastructure shows that the tegument of the metacercaria does not strongly differ from that of adults. The brush-shaped spines of P. macrostomum are similar to those reported for Pygidiopsis summa and Pygidiopsis ardeae, but no differences in spine shape were observed throughout the body.
The trematode Acanthocollaritrema umbilicatum Travassos, Freitas and Bührnheim 1965 is redescribed and data on its life cycle are provided for the first time. Adults were obtained from the common snook, Centropomus undecimalis (Bloch 1792), and both rediae and cercariae from the snail Heleobia australis (d'Orbigny 1835), a new intermediate host. Metacercariae were found encysted among the scales, fins, and musculature and in the buccal cavity of naturally infected fishes, Poecilia vivipara Bloch and Schneider, 1801, Jenynsia multidentata (Jenyns 1842), and Phalloptychus januarius (Hensel 1868), all new intermediate hosts. The examination of the type and freshly obtained adults of A. umbilicatum has shown that they possess 54-64 circumoral spines, in a double row. Experimental infections were achieved in the intermediate hosts H. australis and P. vivipara.
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