A new species of Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000 (Monogenoidea: Dactylogyridae) from South American freshwater catfishes (Siluriformes: Pimelodidae).

Ameloblastella martinae n. sp. is described from the gills of the pimelodid catfishes (Siluriformes: Pimelodidae) Sorubim lima (Bloch & Schneider) (type-host) and Hemisorubim platyrhynchos (Valenciennes) in the Peruvian Amazonia, and on Pseudoplatystoma corruscans (Spix & Agassiz) and P. recticulatum Eigenmann & Eigenmann in Argentina. The new species is distinguished from other congeners mainly by the morphology of the male copulatory organ (MCO), which has a form of a corkscrew with tight rings, whereas in other species of Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000, the MCO is formed by a delicate and coiled tube forming loose rings. Sclerotised structures (haptoral elements and MCO) of specimens of A. martinae n. sp. were used to compare two parasite populations (from Peru and Argentina) using Euclidean distances. Despite the geographical isolation and different host-associations, both populations belong to the same species. The phylogenetic position of A. martinae n. sp. was analysed using partial sequences of the 28S rDNA gene along with 46 species of dactylogyrid parasites of siluriforms (Siluriformes) under Maximum Likelihood (ML) and Bayesian Inference (BI) criteria. Phylogenetic reconstructions showed that Ameloblastella represented by five species, including its type-species A. chavarriai (Price, 1936) from the heptapterid Rhamdia guatemalensis and A. martinae n. sp., was recovered as a well-supported monophyletic group (in both analyses, ML and BI). An additional species, Ameloblastella sp., was found on P. corruscans and P. reticulatum in Argentina. The morphology of the MCO and haptoral elements suggests that Ameloblastella sp. may represent a new species. However, the few specimens found and the lack of genetic sequences of this species precluded its formal description.

The description of two new species of Chloromyxum from skates in the Argentine Sea reveals that a limited geographic host distribution causes phylogenetic lineage separation of myxozoans in Chondrichthyes.

During a survey on the myxosporean fauna of Rajiformes from the Atlantic coast of Argentina, in waters off Buenos Aires Province (34°-42°S; 53°-62°W), the gall bladders of 217 specimens belonging to seven species of skates, representatives of two families, were examined. As a result, three species of Chloromyxum Mingazzini, 1890, namely C. atlantoraji n. sp., C. zearaji n. sp. and C. riorajum Azevedo, Casal, Garcia, Matos, Teles-Grilo and Matos, 2009 were found infecting three endemic host species, the spotback skate Atlantoraja castelnaui (Arhynchobatidae), the yellownose skate Zearaja chilensis (Rajidae) and the Rio skate Rioraja agassizii (Arhynchobatidae), respectively. These species were described based on myxospore morphology and morphometry characterization, as well as by providing their small subunit ribosomal DNA (SSU rDNA) sequences. The SSU rDNA-based phylogenetic analyses showed that these three species constituted a well-established monophyletic subclade within the marine Chloromyxum clade, while branches subtending the other Chloromyxum species were poorly resolved or unresolved, independently of the host taxonomic identities (Carchariniformes, Myliobatiformes, Orectolobiformes, Pristiophoriformes, Rajiformes, Squaliformes and Torpediniformes) and/or host geographic distribution (Atlantic coast of Portugal, Atlantic coast of the USA, Australian waters or Mediterranean Sea). The possible causes of these discrepancies are discussed, providing new insights into the phylogeny of the marine Chloromyxum clade.

Distribution of anisakid nematodes parasitizing rajiform skates under commercial exploitation in the Southwestern Atlantic.

In order to evaluate the infestation by anisakids present in elasmobranchs and their distribution in the Argentine Sea, this study was carried at a regional scale with the following aims: 1) to identify those anisakid species present in skates under exploitation; 2) to characterize quantitatively these infestations and 3) to determine those factors driving the variability in parasite burdens across skate species. A total of 351 skates, belonging to 3 species (218 Sympterygia bonapartii, 86 Zearaja chilensis and 47 Atlantoraja castelnaui) and from different localities of the Argentine Sea were examined for anisakids. Parasites were found in the stomach wall at high prevalence in some samples. Based on morphology and mtDNA cox2 sequences analyses (from 24 larval worms), specimens were identified as Anisakis berlandi, A. pegreffii and Pseudoterranova cattani; the last two known as potentially pathogenic for humans. Differential distribution patterns were observed across parasite and hosts species. In general, fish caught in southern and deeper waters exhibited higher loads of Anisakis spp., whereas infestation levels by P. cattani increase in larger skates. Taking into account that the mere presence of worms or their antigens in fish meat can provoke allergic responses, information on distribution of parasites and their variability is essential for the implementation of food safety practices.