Transmission of Corynosoma australe (Acanthocephala: Polymorphidae) from fishes to South American sea lions Otaria flavescens in Patagonia, Argentina.

Acanthocephalans display a two-host life cycle that involves arthropods as intermediate hosts and vertebrates as definitive hosts. Some species also use paratenic hosts to bridge the trophic gap between both obligatory hosts. However, the relative role of these paratenic hosts in the transmission to definitive hosts has seldom been assessed quantitatively. We report on infection patterns of cystacanths of Corynosoma australe Johnston, 1937 in 20 common teleost species and the Argentine shortfin squid Illex argentinus (Castellanos) from the Patagonian shelf of Argentina. We also explore the role of different fish species in the transmission of C. australe to the most important definitive host in the area, i.e. the South American sea lion Otaria flavescens Shaw. Cystacanths of C. australe were found in all host species except Heliconus lahillei Norman, Merluccius hubbsi Marini and I. argentinus. In eight fish species, the prevalence of C. australe was > 50% and mean intensity > 4, i.e. Acanthistius patachonicus (Jenyns), Nemadactylus bergi (Norman), Paralichthys isosceles Jordan, Percophis brasiliensis Quoy & Gaimard, Prionotus nudigula Ginsburg, Scomber colias Gmelin, Raneya brasiliensis (Kaup) and Xystreurys rasile (Jordan). Two surveys on the trophic ecology of South American sea lions in the study area consistently found a generalist diet dominated by M. hubbsi, and data on the frequency of occurrence and number of other fish and cephalopod species in stomach contents strongly suggest that only R. brasiliensis may play a prominent role in the transmission of C. australe. This result raises interesting questions on the costs of paratenicity.

Gastrointestinal parasites of bottlenose dolphins Tursiops truncatus from the extreme Southwestern Atlantic, with notes on diet composition.

We surveyed the gastrointestinal tracts of 6 bottlenose dolphins Tursiops truncatus from Patagonia to check for helminth parasites and characterize dolphin diet. All dolphins harbored parasites (6477 helminths). We recorded 7 species, including nematodes Anisakis simplex s.l., Pseudoterranova decipiens, acanthocephalans Corynosoma cetaceum, C. australe, and digeneans Braunina cordiformis, Pholeter gastrophilus and Synthesium tursionis. Among the gastric helminths, the most prevalent species were C. cetaceum and A. simplex while C. australe and S. tursionis inhabited the intestine at low prevalence. This is the first report of C. australe and P. decipiens in bottlenose dolphins. Regarding diet, 5 stomachs contained food remains (consisting of 103 prey items). The most important prey species were Geotria australis and Stromateus brasiliensis, but their role in parasite transmission is unclear. At the community level, the gastrointestinal parasite community of T. truncatus was depauperate and strongly overlapped the community described for pelagic dolphins inhabiting Patagonia, suggesting a strong local influence in shaping helminth communities. Nevertheless, these observations are at odds with the notion that oceanic cetaceans have comparatively poorer helminth fauna than neritic species such as bottlenose dolphins, due to the lower likelihood of parasite exchange.

Marine fish imported from Argentina as source of human diphyllobothriosis in Europe? Ecological evidence from dolphins.

Diphyllobothriosis caused by the Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum) is an emerging parasitic disease reported also from non-endemic areas, including Europe (Spain). The origin of these human cases is unknown but should be related to fresh marine fish imported from endemic areas. In this study, we molecularly confirmed common dolphins Delphinus delphis off Argentina as euparatenic transit hosts of A. pacificus. Preliminary analysis of their stomach content, together with data from previous studies from the Southwest Atlantic, showed that common dolphins feed almost exclusively on schooling Argentine hake Merluccius hubbsi and Argentine anchovy Engraulis anchoita. Therefore, we suggest that Argentine hake and Argentine anchovy may represent the intermediate hosts of A. pacificus in the Southwest Atlantic, but also in Europe to where M. hubbsi is imported on ice (unfrozen).

Acanthocephalans from Marine Fishes from Patagonia, Argentina.

In this study, 542 individual fish from 20 species from the Patagonian continental shelf of Argentina were examined for acanthocephalans. A total of 1,547 acanthocephalans belonging to 5 species were collected from 18 species of fish. Adult forms were represented by 2 species: Aspersentis johni ( Baylis, 1929 ) (Heteracanthocephalidae) from longtail southern cod, Patagonotothen ramsayi (Regan) (new host record), and Breizacanthus aznari Hernández-Orts, Alama-Bermejo, Crespo, García, Raga and Montero, 2012 (Arhythmacanthidae) from raneya, Raneya brasiliensis (Kaup). Immature worms of B. aznari were also collected from the intestine of pink cusk-eel, Genypterus blacodes (Forster) (new host record). Cystacanths of 3 species of Corynosoma Lühe, 1904 (Polymorphidae) were found encapsulated in the mesenteries of fish. Corynosoma australe Johnston, 1937 was the most abundant acanthocephalan in our study, infecting 18 species of fish and accounting for >89.9% of all specimens collected. A cystacanth of Corynosoma bullosum (Linstow, 1892) was found in "castañeta", Nemadactylus bergi (Norman) (new host record), and cystacanths of Corynosoma cetaceum Johnston and Best, 1942 were collected from red searobin, Prionotus nudigula Ginsburg, and flounders Paralichthys isosceles Jordan (new host record) and Xystreurys rasile (Jordan). The Patagonian shelf of Argentina represents a new locality record for A. johni and C. bullosum. This survey is a starting point for understanding the diversity of marine acanthocephalans in Patagonian waters.

A checklist of the helminth parasites of marine mammals from Argentina.

Based on published records and new data accumulated by the authors, we generated a list of the helminth parasites of marine mammals from off the coast of Argentina. We found 49 reports of helminths parasitizing cetaceans and pinnipeds from Argentina from 1952 to 2015. The list includes 54 taxa of helminths (8 acanthocephalans, 24 nematodes, 11 cestodes and 11 trematodes) associated with 18 species of cetaceans and 5 species of pinnipeds. Most of the records represent adults (5 acanthocephalans, 16 nematodes, 6 cestodes and 11 trematodes), followed by larvae (10 nematodes and 3 metacestodes) and juveniles (4 acanthocephalans and 2 cestodes). The checklist contains 24 named species (5 acanthocephalans, 8 nematodes, 4 cestodes and 7 trematodes) and 30 undetermined helminth taxa (3 acanthocephalans, 16 nematodes, 7 cestodes and 4 trematodes). The present account contains a parasite/host lists and information on the habitat, developmental stage and distribution of the parasites listed, repositories of their type and voucher specimens and references. A host-parasite list is also presented. The data compiled on the helminth of marine mammals from Argentina in the present study revealed gaps in the knowledge of their taxonomic identification, composition, distribution, host specificity and life cycles. These gaps are also briefly discussed in order to provide an outline for future research.

Uterine adenocarcinoma with generalised metastasis in a bottlenose dolphin Tursiops truncatus from northern Patagonia, Argentina.

An endometrial adenocarcinoma with areas of squamous differentiation and generalised metastasis was observed in a bottlenose dolphin Tursiops truncatus stranded in northern Patagonia in July 1997. This is the second report of a uterine adenocarcinoma in a free-living cetacean and the first in a Delphinidae. This neoplasm likely compromised reproduction for several years. In addition, the dolphin presented tattoo-like skin lesions and its digestive tract was infested by Anisakis simplex, Pseudoterranova sp., Braunina cordiformis and Corynosoma australe.

Stable isotopes indicate population structuring in the southwest Atlantic population of right whales (Eubalaena australis).

From the early 17th century to the 1970s southern right whales, Eubalaena australis, were subject to intense exploitation along the Atlantic coast of South America. Catches along this coast recorded by whalers originally formed a continuum from Brazil to Tierra del Fuego. Nevertheless, the recovery of the population has apparently occurred fragmentarily, and with two main areas of concentration, one off southern Brazil (Santa Catarina) and another off central Argentina (Peninsula Valdés). This pattern suggests some level of heterogeneity amongst the population, which is apparently contradicted by records that traced individuals moving throughout the whole geographical extension covered by the species in the Southwest Atlantic. To test the hypothesis of the potential occurrence of discrete subpopulations exploiting specific habitats, we investigated N, C and O isotopic values in 125 bone samples obtained from whaling factories operating in the early 1970s in southern Brazil (n=72) and from contemporary and more recent strandings occurring in central Argentina (n=53). Results indicated significant differences between the two sampling areas, being δ13C and δ18O values significantly higher in samples from southern Brazil than in those from central Argentina. This variation was consistent with isotopic baselines from the two areas, indicating the occurrence of some level of structure in the Southwest Atlantic right whale population and equally that whales more likely feed in areas commonly thought to exclusively serve as nursing grounds. Results aim at reconsidering of the units currently used in the management of the southern right whale in the Southwest Atlantic Ocean. In the context of the current die-off affecting the species in Peninsula Valdés, these results also highlight the necessity to better understand movements of individuals and precisely identify their feeding areas.

Description, microhabitat selection and infection patterns of sealworm larvae (Pseudoterranova decipiens species complex, nematoda: ascaridoidea) in fishes from Patagonia, Argentina.

BACKGROUND: Third-stage larvae of the Pseudoterranova decipiens species complex (also known as sealworms) have been reported in at least 40 marine fish species belonging to 21 families and 10 orders along the South American coast. Sealworms are a cause for concern because they can infect humans who consume raw or undercooked fish. However, despite their economic and zoonotic importance, morphological and molecular characterization of species of Pseudoterranova in South America is still scarce. METHODS: A total of 542 individual fish from 20 species from the Patagonian coast of Argentina were examined for sealworms. The body cavity, the muscles, internal organs, and the mesenteries were examined to detect nematodes. Sealworm larvae were removed from their capsules and fixed in 70% ethanol. For molecular identification, partial fragments of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1) were amplified for 10 isolates from 4 fish species. Morphological and morphometric data of sealworms were also obtained. RESULTS: A total of 635 larvae were collected from 12 fish species. The most infected fish was Prionotus nudigula, followed by Percophis brasiliensis, Acanthistius patachonicus, Paralichthys isosceles, and Pseudopercis semifasciata. Sequences obtained for the cox1 of sealworms from A. patachonicus, P. isosceles, P. brasiliensis and P. nudigula formed a reciprocally monophyletic lineage with published sequences of adult specimens of Pseudoterranova cattani from the South American sea lion Otaria flavescens, and distinct from the remaining 5 species of Pseudoterranova. A morphological description, including drawings and scanning electron microscopy photomicrographs of these larvae is provided. Sealworms collected from Argentinean fishes did not differ in their diagnostic traits from the previously described larvae of P. cattani. However a discriminant analysis suggests that specimens from P. nudigula were significantly larger than those from other fishes. Most of the sealworms were collected encapsulated from the muscles and, to a lesser degree, from the mesenteries and the liver. CONCLUSIONS: We provided the first molecular identification, morphological description and microhabitat characterization of sealworm larvae from the Argentinean Patagonian coast. We also reported the infection levels of sealworms on 20 fish species in order to elucidate the life cycle of these nematodes in this area.