Host-parasite relationship of Ortholinea lauquen sp. nov. (Cnidaria: Myxozoa) and the fish Galaxias maculatus in northwestern Patagonia, Argentina.

Galaxias maculatus (Jenyns, 1842) is a widespread freshwater fish and an important component of the economically important whitebait fisheries across the Southern Hemisphere. We report a new myxosporean parasite (Cnidaria: Myxozoa) infecting the kidney of G. maculatus from northwestern Patagonia (Argentina). Ortholinea lauquen sp. nov. was characterized using myxospore morphology, morphometrics and small subunit rDNA (ssrDNA) sequence data. Our ssrDNA phylogenetic analyses showed that O. lauquen sp. nov. is a member of the oligochaete-freshwater urinary tract clade and basal to a clade containing 4 different spore morphotypes (Chloromyxum, Myxidium, Zschokkella, Hoferellus). We explored host-parasite relationships at the macro- and microscale by analyzing the distribution, tissue tropism and pathology of O. lauquen sp. nov. Prevalence was relatively low (7%) by microscopy, but PCR detection revealed hidden levels of infection (49%), with the highest detection in lakes Morenito and Moreno (63-90%, Río Negro Province). The only locality negative by both microscopy and PCR was the Caleufu River (Neuquén Province), suggesting differences in fish life history traits (landlocked vs. potamodromous) or preference of the putative obligate invertebrate host for lentic habitats. O. lauquen sp. nov. sporulates in the renal tubules and occasionally in the glomerular space. The plasmodia frequently occluded the tubule lumina, and cellular necrosis and disintegration of the epithelium were observed. O. lauquen sp. nov. could represent a potential threat to G. maculatus culture under intensive farming conditions.

Do environmental differences between lakes in northwestern Argentinean Patagonia affect the infection of Philureter trigoniopsis (monogenea) in Galaxias maculatus (osmeriformes)?

Philureter trigoniopsis is the only parasite found in the ureters and urinary bladder of Galaxias maculatus in Patagonian Andean lakes. The dynamics of this endoparasitic monogenean were studied in Lake Gutiérrez, a body of water with scarce shoreline vegetation, where the host has an annual cycle of migration to the deep pelagic zone of the lake. To compare variations of the infection related to differences between lakes, G. maculatus specimens were sampled monthly with baited traps from September 1998 to November 1999 in Lake Moreno, which is an oligotrophic body of water with emergent shoreline vegetation and where the fish do not migrate to the deep pelagic areas of the lake. In addition, data for summer infections of P. trigoniopsis from 10 Andean Patagonian lakes that differ in aquatic vegetation, depth, and area were compared. In Lake Moreno prevalence of P. trigoniopsis showed a seasonal pattern, with 1-yr-old fish exhibiting the highest values of prevalence and mean intensity. Negative correlations between water temperature and prevalence and between age of fish and abundance were found. Our results suggest that age of fish may be the main factor structuring the distribution of P. trigoniosis in populations of G. maculatus. At the regional level the relationship between the infection and the characteristics of the lakes was also observed, with prevalence and mean intensity of P. trigoniopsis in G. maculatus higher in large deep lakes without macrophytes.

Philureter trigoniopsis, a new genus and species (Dactylogyridae, Ancyrocephalinae) from the ureters and urinary bladder of Galaxias maculatus (Osmeriformes: Galaxiidae) in Patagonia (Argentina).

The monotypic Philureter n. gen. (Ancyrocephalinae; Dactylogyridae) is proposed to accommodate Philureter trigoniopsis n. sp. with the following features: presence of a cuplike ventral haptor armed with 14 hooks and 2 anchor/bar complexes; dorsal pair of anchors poorly defined and variable in shape, 1 frequently absent; tandem, intercecal gonads, testis bilaterally lobulated. Philureter trigoniopsis n. sp. is described from the ureters and urinary bladder of Galaxias maculatus (Jenyns, 1842) (Osmeriformes) in Patagonian Andean lakes, Argentina.