Verónica R. Flores

Schistosomes with wings: how host phylogeny and ecology shape the global distribution of Trichobilharzia querquedulae (Schistosomatidae)

Migratory waterfowl play an important role in the maintenance and spread of zoonotic diseases worldwide. An example is cercarial dermatitis, caused when larval stages of schistosomes that normally develop in birds penetrate human skin. Members of the genus Trichobilharzia (Schistosomatidae), transmitted mainly by ducks, are considered to be major etiological agents of cercarial dermatitis globally. To better understand the diversity and distribution of Trichobilharzia spp., we surveyed ducks from the United States, eastern Canada, Argentina, South Africa and New Zealand. To aid in species identification of the Trichobilharzia worms recovered, regions of the Cox1, ND4 and ITS1 were sequenced. Furthermore, we provide molecular phylogenetic evidence for the cosmopolitan distribution and trans-hemispheric gene flow for one species, Trichobilharzia querquedulae, previously thought to be restricted to North America. These new samples from endemic non-migratory duck species indicate that T. querquedulae transmission occurs within each of the regions we sampled and that it is specific to the blue-winged+silver teal duck clade. Prevalence within this host group is >95% across the known range of T. querquedulae, indicating that transmission is common. Genetic divergence is evenly distributed among continents, and no phylogenetic structure associated with geography was observed. The results provide strong support for the global distribution and transmission of T. querquedulae and represent, to our knowledge, the first report of a cosmopolitan schistosome confirmed by genetic data. These data are the first known to support trans-hemispheric genetic exchange in a species responsible for causing cercarial dermatitis, indicating that the epidemiology of this group of poorly known zoonotic parasites is more complex than previously expected.

Catatropis hatcheri n. sp. (Digenea: Notocotylidae) from Heleobia hatcheri (Prosobranchia: Hydrobiidae) and notes on its life-cycle in Patagonia, Argentina

A new species of Catatropis Oghner, 1905 from a freshwater Neotropical prosobranch snail, Heleobia hatcheri (Hydrobiidae), is described. Naturally infected snails were collected from Nahuel Huapí Lake in Andean Patagonia. The characteristics of the larval stages are also presented. Experimental adults were recovered from the distal region of the intestinal caeca of chicks and ducklings and natural adults from a wild duck Anas platyrhynchos. Adults of Catatropishatcheri n. sp. can be distinguished from all other species of the genus in having 10–12 (11) ventral glands in each lateral row, the cirrus-sac extending back to between the first third and the middle of the body, the metraterm shorter than the cirrus-sac, a previtelline field of 1,258–1,544 (1,396), vitelline follicles reach back to the anterior border of the testes with some follicles extending slightly lateral to them, only external testicular margin lobed and genital pore in median line just posterior to the intestinal bifurcation. In addition, the eggs have one filament on each pole, the rediae contain one or two mature cercariae, and the cercariae are tri-oculate, with a long tail and encyst in the environment.

Steganoderma szidati n. sp. (Trematoda: Zoogonidae) from Galaxias maculatus (Jenyns) and G. platei Steindachner in Patagonia, Argentina.

Steganoderma szidati n. sp. is described from the intestine of two freshwater fishes, Galaxias maculatus and G. platei (Galaxiidae), from Andean lakes in Patagonia, Argentina. This freshwater zoogonid species fits in the genus Steganoderma (sensu Bray, 1987) because of the length of the caeca and the position of the vitelline follicles. The new species is characterised by possesing 6-13 vitelline follicles situated between the anterior margin of the ventral sucker and the poterior margin of the testis. The gonads are in the anterior hindbody and the ovary is anterior to the right testis. The cirrus has two conspicuous spines at its distal end, and the seminal vesicle always exhibits a constriction. The excretory vesicle never reaches the level of the posterior margin of the testes.

Allocreadium pichi n. sp. (Trematoda: Allocreadiidae) in Galaxias maculatus (Osteichthyes: Galaxiidae) from Lake Moreno in Patagonia (Argentina)

Allocreadium pichi n. sp. (Trematoda: Allocreadiidae) is described from the intestine of Galaxias maculatus (Osteichthyes: Galaxiidae) from Moreno Lake in Patagonia, `Argentina. This species is distinguished from A. patagonicum Shimazu, Urawa & Coria, 2000, the other species recorded in the area, by its smaller body size, the diagonal position of the testes and different ratios of the suckers, testes and cirrus-sac in relation to body size. In addition, the synonymy of A. patagonicum withPolylekithum percai Ostrowski de Núñez, Brugni & Viozzi, 2000 is proposed herein.

Allassogonoporus dromiciops n. sp. (Digenea: Allassogonoporidae) from Dromiciops gliroides (Marsupialia: Microbiotheriidae) in Patagonia, Argentina

A new species of Allassogonoporus Olivier, 1938, from a naturally infected specimen of Dromiciops gliroides, is described. Adults of A. dromiciops n. sp. were recovered from the small intestine. This new species can be distinguished from all other species of the genus by having: the largest body and eggs, a lobed testes and ovary, a Y-shaped excretory vesicle and vitelline follicles beginning at the level of the posterior margin of the oral sucker. This is the first record of a species of Allassogonoporus in South America and the first record of a digenean parasitising D. gliroides.

Redescription of Hippocrepis myocastoris Babero, Cabello et Kinoed, 1979 (Digenea: Notocotylidae) in the Coypu Myocastor coypus (Rodentia: Myocastoridae) from Patagonia, Argentina

Abstract Hippocrepis myocastoris Babero, Cabello et Kinoed, 1979 is redescribed from a naturally infected Myocastor coypus Molina (Rodentia: Myocastoridae) captured in the Negro River (40°07′S; 64°27′W) from Patagonia, Argentina. A total of 31 ovigerous specimens were stained and measured. These specimens of H. myocastoris were similar to paratype in morphology and morphometric characteristics, did not have ventral gland, and mature eggs presented 4 polar filaments on opercular pole. This is the first record of a notocotylid parasitizing aquatic rodents in Argentinean Patagonia.

POPULATION DYNAMICS OF TYLODELPHYS DESTRUCTOR AND DIPLOSTOMUM MORDAX (DIGENEA: DIPLOSTOMIDAE) CO-OCCURRING IN THE BRAIN OF PATAGONIAN SILVERSIDES FROM LAKE PELLEGRINI, PATAGONIA, ARGENTINA

Studies on infection patterns of diplostomid parasites in commercially exploited fishes have not been done in Patagonia (Argentina). The aim of this work was to study the population dynamics of two diplostomid species in the brain of Patagonian silversides (Odontesthes hatchery), the interaction between them, and effect on health and physical condition of the hosts. Tylodelphys destructor and Diplostomum mordax metacercariae in the brain of Patagonian silversides in Lake Pellegrini were studied between January 1991 and February 1992. Tylodelphys destructor parasitized all silversides examined; prevalence of D. mordax varied between 7% and 100%. Mean intensity for T. destructor was 35–140 and for D. mordax was 3–49. Highest mean intensities of T. destructor coincided with the lowest mean intensities of D. mordax. Recruitment seems to occur from July–November for T. destructor and from April–June for D. mordax, revealing a temporal segregation with inverse patterns of infection and recruitment. Tylodelphys destructor has higher intensities in the brain of the older fish, whereas D. mordax did not, suggesting another type of segregation. There were no evidences of gross pathology. No covariation between abundance of larvae and condition factor, gonadosomatic index, and gut fullness was detected.