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

Abstract

BackgroundThird-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.MethodsA 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.ResultsA 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.ConclusionsWe 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.

Mitochondrial Phylogenomics yields Strongly Supported Hypotheses for Ascaridomorph Nematodes

“…There is considerable value in employing mt genome markers to explore genetic variation within the genera Pseudoterranova and C. ogmorhini , because phenotypic differentiation is unreliable44. The P. decipiens complex consists of at least five cryptic species (genetically but morphologically indistinguishable), namely P. decipiens, P. azarasi, P. cattani, P. krabbei and P. bulbosa 4546.…”

Diversity of ectoparasites and endoparasites infecting Brachyplatystoma vaillantii (Siluriformes: Pimelodidae), a large migratory catfish from the Amazon

“…This nematode, which can be a serious threat to human health, had a higher prevalence in B. vaillantii than that reported in B. filamentosum from the state of Pará, Brazil (Rodrigues et al 2015). Pseudoterranova are nematodes that infect different marine and freshwater fish species (McClelland 2002;Hernández-Orts et al 2013;Rodrigues et al 2015). Marine Pseudoterranova species have invertebrates (e.g., polychaetes, decapods, copepods, mysids, isopods, etc.)…”

“…Marine Pseudoterranova species have invertebrates (e.g., polychaetes, decapods, copepods, mysids, isopods, etc.) as primary hosts, while fish species are secondary hosts and mammals are definitive hosts (McClelland 2002;Hernández-Orts et al 2013). The life cycle of these endoparasites in freshwater fish is yet unknown but considering what is known of their life cycle in marine environments, the prevalence of Pseudoterranova sp.…”

Contracaecum multipapillatum (Nematoda: Anisakidae) en peces de aguas continentales de Guanacaste, Costa Rica e Izabal, Guatemala

“…También se observó, una alta tendencia de C. multipapillatum por ubicarse formando quistes en órganos viscerales, mientras que la cantidad de quistes adheridos en musculatura fue muy escasa. Estos resultados son similares a los hallados por Álvarez et al (17), Iglesias et al (18) y Hernández et al (19) que relacionan estas características con una baja capacidad de migración del parasito desde vísceras hacia musculatura una vez que el pez ha muerto. Esto es importante, pues determina la capacidad infectiva de las larvas para el ser humano al momento de consumir productos pesqueros.…”