Gustavo P. Viozzi

SEASONALITY OF RECRUITMENT AND REPRODUCTION OF ACANTHOCEPHALUS TUMESCENS (ACANTHOCEPHALA) IN FISHES FROM LAKE MORENO (PATAGONIA, ARGENTINA)

The seasonality of recruitment and reproduction of Acanthocephalus tumescens at the component population level was investigated in Lake Moreno (Patagonia, Argentina). Seasonal samples of the principal fish host species were taken between spring 1999 and spring 2000. Prevalence, mean intensity, coefficient of dispersion, sex ratio, proportion of maturity stages of females, and percentages of the 2 sources of infection in the stomach of fishes were calculated. Overall prevalence, mean intensity, and coefficient of dispersion showed the same pattern of seasonal changes. The seasonal feeding patterns of fishes affect the occurrence of A. tumescens, producing 1 peak in spring and the other peak in autumn. The lower temperature in winter delay reproductive processes after the autumn period of recruitment.

Metazoan Parasites of Galaxias maculatus (Osmeriformes: Galaxiidae) from Argentinean Patagonia

Abstract A checklist, based on bibliographical records and original data from an extensive survey, is presented for the metazoan parasites of Galaxias maculatus (Jenyns, 1842) in Argentinean Patagonia. The checklist includes 33 metazoan parasite entries: 5 myxozoans, 12 digeneans, 2 monogeneans, 3 cestodes, 2 acanthocephalans, 7 nematodes, 1 copepod, and 1 bivalve. Gyrodactylus sp., Pomphorhynchus patagonicus Ortubay, Úbeda, Semenas and Kennedy, 1991, and Hysterothylacium patagonense Moravec, Urawa and Coria, 1997 are reported for the first time from G. maculatus in South America. Although this checklist enlarges the knowledge of G. maculatus parasites, a large portion of Patagonia remains unexplored, and many of its lakes and rivers have never been surveyed for parasites, especially in the southern part of the region.

LIFE-CYCLE STAGES OF A POSTHODIPLOSTOMUM SPECIES (DIGENEA: DIPLOSTOMIDAE) FROM PATAGONIA, ARGENTINA

Abstract: In Patagonia, populations of the galaxiid fish Galaxias maculatus are parasitized by metacercariae of a species of Posthodiplostomum (Digenea: Diplostomidae). The aim of this work was to describe larval and adult stages of this species in experimental and natural hosts from an Andean Patagonian lake. Specimens of G. maculatus and the pulmonate snail, Anisancylus obliquus, were collected in Patagua Lake. The snails were isolated in individual containers to observe emergence of cercariae, dissected, and examined under a stereoscopic microscope to record sporocysts and cercariae. Fish were examined to obtain metacercariae, and uninfected fish from Gutiérrez Lake were exposed to cercariae from A. obliquus to obtain experimental metacercariae. Chicks and mice were infected with metacercariae from naturally infected G. maculatus to obtain experimental adults. Specimens recovered belong to Posthodiplostomum sp. on the basis of morphological features. This is the first description of sporocysts, cercariae, metacercariae, and adults stages of a Posthodiplostomum species in Patagonia, including data about its natural intermediate hosts.

A NEW HEDRURID SPECIES (NEMATODA) FROM GALAXIID FISHES IN PATAGONIA (ARGENTINA) AND INFECTION OF AMPHIPODS AS INTERMEDIATE HOST

Abstract During a parasite survey of galaxiid fishes (Galaxiidae) from Patagonian Andean lakes, a new species of nematode, Hedruris suttonae n. sp. was collected from the stomach of the native Galaxias maculatus (Jenyns) and G. platei (Steindachner). Specimens were examined by light and scanning electron microscopy, especially head morphology, female caudal prehensile structure, and distribution of spines. The new species is distinguished by body and tail size, morphology and size of spicules, the arrangement of caudal papillae in the male, the female caudal hook, and size of eggs. Hyalella patagonica (Ortmann), a Neotropical species of Amphipoda, is reported as its natural intermediate host. Data regarding prevalence and mean intensity in the intermediate and definitive hosts are included. The diet and habitat of the hosts, the percentage of gravid females, the high values of prevalence, and mean intensity in galaxiid fishes, as well as the wide distribution of H. suttonae, collectively indicate that, in these oligotrophic Andean lakes, G. maculatus and G. platei are true definitive hosts of this nematode.

Macroparasites of the Invasive Fish, Cyprinus carpio, in Patagonia, Argentina

ABSTRACT: The common carp (Cyprinus carpio L.) is probably the most widely distributed freshwater fish species and is cultured on almost all continents. In South America, studies on the parasites from C. carpio are limited. The aim of the present study was to report on the macroparasites from wild C. carpio populations inhabiting the Neuquen River, which is at the southernmost distribution of C. carpio in Argentina. From spring 2011 to winter 2012, four seasonal samples of C. carpio were collected from the Neuquen River at the Ingeniero Ballester dam using gill nets. Fish were dissected and all organs were examined using microscopy. All macroparasites were determined and counted and their prevalences and mean intensities calculated. In total, 33 fish were examined and the following six parasites were recorded: the monogeneans Dactylogyrus extensus (gills) and Pseudacolpenteron sp. (in the canals of the scales along the lateral line system); the cestode Bothriocephalus sp. (intestine); the nematode Contracaecum sp. (liver and visceral fat); and the acanthocephalans Pomphorhynchus patagonicus (intestine and liver) and Polymorphus sp. (liver and wall of intestine). The monogenean D. extensus was the most commonly encountered species and had the highest prevalence and mean intensity of all parasites detected. This study reports 6 new records of parasite species in C. carpio from Argentina.

A NEW GENUS OF DACTYLOGYRID FROM THE GILLS OF GALAXIAS MACULATUS (OSMERIFORMES: GALAXIIDAE) IN MAULLIN BASIN, PATAGONIA, CHILE

During a parasitological survey of Galaxias maculatus (Jenyns, 1842) in the Maullín Basin (Chilean Patagonia), specimens of a new species of Monogenea were collected from the gills. This species is described as the only member of a proposed new genus, Inserotrema n. gen. (Dactylogyridae, Ancyrocephalinae), characterized by similar hooks with 2 subunits, overlapping gonads, coiled cirrus with counterclockwise rings, articulated accessory piece formed by 2 parts, a needlelike sclerite threading the distal part of the MCO, and a sclerotized midventral vagina. This new genus is proposed for dactylogyrids from gills of galaxiids (Galaxiidae). Inserotrema puyei n. sp. infects gills of G. maculatus from Llanquihue Lake, Maullín River, and Maullín Estuary. This is the first species of Ancyrocephalinae described from gills of a galaxiid.

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.

THE RELATIONSHIP BETWEEN FISH ASSEMBLAGES AND THE HELMINTH COMMUNITIES OF A PREY FISH, IN A GROUP OF SMALL SHALLOW LAKES

Abstract Galaxias maculatus (small puyen) is an abundant native fish distributed in lakes and rivers of the Patagonia, and it is the frequent prey of other fishes, fish-eating birds, and mammals. Previous studies have shown that it is parasitized by 33 metazoan species and that the richness and composition of the parasite communities vary between lakes. The aim of the present work was to analyze the relationship between the composition of fish assemblages and the helminth component community structure of G. maculatus. Ten environmentally similar, small, shallow lakes, belonging to the Nahuel Huapi Lake basin, were chosen because of the differences in the native fish assemblages. Parasite community structure in G. maculatus varied according to the fish assemblage of each lake. The presence of the piscivorous fish Percichthys trucha regularly produced variations in the composition and richness at the component and infracommunity levels, as well as the percentage of autogenic parasite species in G. maculatus.

Infection of Myxobolus galaxii (Myxozoa) in Galaxias maculatus (Osmeriformes: Galaxiidae) From Northwestern Patagonian Andean Lakes (Argentina)

The infection of Myxobolus galaxii Szidat, 1953, from the musculature and abdominal organs of northwestern Patagonian Galaxias maculatus is described. Plasmodia are histozoic and intercellular. Spores are pyriform in valvar view and biconvex in sutural view, with 4–9 edge notches in the sutural line, varying in shape within the same plasmodium. Myxobolus galaxii was detected in fish from 7 of 17 Andean Patagonian lakes, with prevalences ranging between 2 and 17%. A repeating pattern of summer increment in prevalence was observed, which could be explained by the ontogenetic migratory movements of the fish in Lake Gutiérrez. Also, accumulation of plasmodia through the life span of fish was detected.

New Cystidicolid Species (Nematoda) From Galaxias platei (Osmeriformes: Galaxiidae) in Patagonian Freshwater Environments

During a parasitological survey of Galaxias platei Steindachner, 1898, from Patagonian Andean Lakes, a new species of Cystidicolidae was found in the stomach of fish. The new species was described using light and scanning electron microscopy; the species has characteristics of Ascarophis and is distinguishable from other species by a combination of the following features: well-developed pseudolabia with T-shaped inner extensions, bifurcate deirids, small ratio GE:ME, small left spicule, small ratio LS:RS, and larvigerous eggs with thick and fine filaments in both poles. Intraspecific variation in the morphology of larvigerous eggs was studied. This is the first species of Ascarophis described from freshwater fishes.