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Seasonal variability in the gut ultrastructure of the parasitic copepod Neoergasilus japonicus (Copepoda, Poecilostomatoida)

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Abstract:

The gut structure and ultrastructure of Neoergasilus japonicus (Harada, 1930), a copepod from the family Ergasilidae (Copepoda, Poecilostomatoida) and a parasite of fish, were compared at different periods of the life cycle: in free-living specimens in October and after attaching to fish in January and June. Differences in the depth of the intestinal epithelium were prominent and other cellular characteristics appeared seasonally variable. We relate these to changes in the physiological activity. Preliminary data from stable-isotope analyses of attached specimens suggest nutritional contribution from parasitism. The possibility of a diapause in the life cycle, as well as the relationship between the morphology of the gut and early evolutionary parasitism of N. japonicus, are discussed.

La structure et l'ultrastructure du tube digestif de Neoergasilus japonicus (Harada, 1930), un copépode, parasite de poissons (Copepoda, Poecilostomatoida, Ergasilidae), ont été comparées à différentes périodes de son cycle biologique, chez les individus libres au mois d'octobre et chez les individus fixés sur l'hôte, en janvier et en juin. Il y a des variations saisonnières importantes des caractéristiques cellulaires, en particulier, dans l'épaisseur de l'épithélium intestinal. Nous croyons que ces variations sont dues aux changements de l'activité physiologique. Des données préliminaires provenant de l'analyse des isotopes stables chez les individus fixés laisse croire à l'implication du parasitisme dans la nutrition de N. japonicus. La possibilité d'une période de diapause dans le cycle biologique, ainsi que l'existence d'une relation entre la morphologie du tube digestif et le passage récent au parasitisme dans l'évolution de N. japonicus, font l'objet d'une discussion.

Document Type: Research Article

Publication date: 2004-10-01

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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