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Formation of the gut in the first two naupliar stages of Acartia clausi and Hemidiaptomus roubaui (Copepoda, Calanoida): comparative structural and ultrastructural aspects

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In this study, the structure and ultrastructure of the digestive system are compared in the early larval stages (nauplii I and II) of two copepod calanoid species, Acartia clausi Giesbrecht, 1889 and Hemidiaptomus roubaui Richard, 1888. The nauplii I of both species have no functional digestive tract, which is represented initially only by a blind esophageal slit and yolky endodermal cells, which fill the most part of the naupliar body, whereas at the nauplius II stage the differentiated digestive tract becomes functional. The resorption cavity corresponding to the future midgut is progressively formed in the endodermal mass during the premolt phase; it is surrounded by differentiating epithelial cells. In the ecdysial phase the foregut has associated labral glands, the midgut young R-, B-, and R'-cells of epithelium, and there is a short open hindgut.

La structure et l'ultrastructure du tube digestif ont été étudiées comparativement sur des stades larvaires (nauplii I et II) de deux espèces de copépodes calanoïdes, Acartia clausi Giesbrecht, 1889 et Hemidiaptomus roubaui Richard, 1888. Chez les nauplii I, l'appareil digestif n'est pas développé. Seule une fente œsophagienne aveugle est présente, la plus grande partie du corps étant occupée par une masse de cellules endodermiques, riches en vitellus. Les nauplii II possèdent un tube digestif fonctionnel. L'intestin moyen s'édifie progressivement, pendant la phase de prémue, à partir d'une cavité de résorption formée au sein de la masse endodermique et entourée d'une enveloppe de cellules épithéliales en cours de différenciation. Au moment de la mue, le nauplius est pourvu d'un œsophage avec des glandes labrales associées, d'un intestin moyen dont l'épithélium révèle trois types de cellules (R, B et R' ) et d'un court intestin postérieur ouvert.
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Document Type: Research Article

Publication date: 2002-02-01

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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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