Maria Luiza Gaspar Goulart Dias

The life cycle of Clinostomum complanatum Rudolphi, 1814 (Digenea, Clinostomidae) on the floodplain of the high Paraná river, Brazil

The life cycle of the digenetic trematode Clinostomum complanatum was studied on the floodplain of the high Paraná river, Brazil. Sampling was done between June 1999 and June 2000. The mollusc Biomphalaria peregrina was the first intermediate host with a prevalence of infection of 0.75%. The fish Loricariichthys platymetopon, Hoplosternum littorale, Parauchenipterus galeatus, Hoplias malabaricus and Loricaria sp. were second intermediate hosts, with the prevalence varying from 2.45% (H. malabaricus) to 60.8% (L. platymetopon). The birds Ardea cocoi, Phalacrocorax brasilianus, Egretta alba and Egretta thula were definitive hosts, with the prevalence ranging between 5.5% (E. thula) and 95% (A. cocoi). The high prevalences in birds, especially in A. cocoi, suggest some kind of mechanism facilitating the predation of infected fish. The importance of the various hosts is discussed, and it is concluded that the floodplain of the high Paraná river has suitable conditions for the maintenance of the life cycle of C. complanatum.

Ecology of Clinostomum complanatum Rudolphi, 1814 (Trematoda: Clinostomidae) infecting fish from the floodplain of the high Paraná River, Brazil

The prevalence of Clinostomumcomplanatum Rudolphi, 1814 (Digenea, Clinostomidae) in fishes Loricariichthysplatymetopon, Parauchenipterusgaleatus and Hoplosternumlittorale, which are second intermediate hosts, was studied at the floodplain of the high Paraná River, Brazil. Season (alternation flood–drought), habitat (lentic and semi-lotic), and sex were not related to its prevalence. For L. platymetopon, the immature and smaller fish had the lowest prevalence, whilst the opposite was observed for P. galeatus and H. littorale. This suggests that the probability of being predated is unchanged by parasitism for L. platymetopon; thus, a cumulative effect of repeated infections is observed; for the two other species, the highest parasitised fish may have higher predation mortality rates. While H. littorale is the preferred item in birds’ diet, L. platymetopon is the most abundant fish species and has the highest C. complanatum prevalence, which makes it the most likely path of transmission to the bird, the definitive hosts of C. complanatum.

Scanning electron microscopy of Ithyoclinostomum dimorphum (Trematoda: Clinostomidae), a parasite of Ardea cocoi (Aves: Ardeidae)

Scanning electron microscopy is used for the first time to study the surface topography of Ithyoclinostomum dimorphum (Diesing, 1850), collected from Ardea cocoi Linnaeus, 1766 on the floodplain of the upper Paraná River Basin, Brazil. The body surface exhibits annular furrows, ridges and sensory papillae but no spines, and the tegument is reticulate. The oral sucker is terminal, bears radial furrows and is surrounded by a collar. The ventral sucker is located close to the oral sucker but lacks a collar. When extruded, the cirrus can be seen to bear papillae in its base, and the aperture of the ejaculatory duct is visible distally. The excretory pore is dorso-subterminal. Various incrustations and secretions are present on the body surface. These detailed observations make it possible for to us speculate on the functional significance of some of our findings in relation to the large size and contractile nature of these worms, and their ability to survive and mate in an apparently hostile environment.