Molecular identification of Contracaecum pelagicum (Nematoda: Anisakidae) from the anchovy Engraulis anchoita (Engraulidae) and fish-eating birds from Argentinian North Patagonian Sea, with larval morphological description.

LUCAS E. GARBIN; SIMONETTA MATTIUCCI; MICHELA PAOLETTI; JULIA I. DIAZ; GIUSEPPE NASCETTI; GRACIELA T. NAVONE

Parasitology Internacional

Elsevier

Lugar: Kiyotake; Año: 2011

1383-5769

Anisakids use invertebrates as paratenic or intermediate hosts as a basic feature on larval transmission. The third-stage larva usually develops in invertebrates which are prey items of vertebrate paratenic hosts as fishes. Contracaecum larvae moult twice inside eggs and hatch as free third-stage larvae ensheated in the second-stage larva cuticle. Copepods act as paratenic or obligated host usually ingesting these free L3 larvae and fish would act as paratenic or metaparatenic host preying on infected copepods. Fish-eating birds acquire L3 larvae ingesting infected fish developing the fourth-stage larvae and adults. Objective of this work was to establish the specific correspondence between C. pelagicum L3 larvae parasitizing Engraulis anchoita, and the adults parasitizing Spheniscus magellanicus and Phalacrocorax atriceps through the use of molecular markers. Sixteen specimens of Contracaecum L3 larvae were analyzed from E. anchoita from Bahía Engaño, Chubut, eight adult nematodes from S. magellanicus and six adult specimens from Ph. atriceps both from Península Valdés, Chubut. All nematodes were sequenced for genes mitochondrial cytochrome oxidase 2 (mtDNA cox2), mitochondrial ribosomal RNA gene (rrnS), and the ITS1 and ITS2 sequence regions. Phylogenetic analysis were performed by using Maximum Parsimony (MP) analysis by PAUP, Akaike Information Criterion (AIC) by Modeltest 3.6. Also, studies under SEM and OM were done on L3 larvae. All L3 larvae individuals from E. anchoita, adults from S. magellanicus, and Ph. atriceps clustered in the same clade well supported in the MP tree inferred from the mtDNA cox2, and rrnS gene sequences analysis. Further, the sequence alignments of L3 larvae and adults of C. pelagicum here obtained at the ITS-1 and ITS-2 regions of the rDNA were found to be distinct from those so far obtained in other Contracaecum spp. genetically characterized. The MP trees topologies obtained mtDNA cox2 and rrnS genes demonstrated that specimens of Contracaecum L3 larvae from E. anchoita and C. pelagicum from S. magellanicus as well as from Ph. atriceps constitute a unique clade well-distinct and supported one from all the others formed by Contracaecum spp. sequenced so far for these genes. Molecular markers are considered to be an effective tool on larval transmission.