Paratylenchinae: postembryonic developmental stages of Paratylenchus straeleni (De Coninck, 1931) and P. steineri Golden, 1961 (Nematoda: Tylenchulidae)

in Nematology
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Postembryonic developmental stages of naturally occurring populations of Paratylenchus straeleni and P. steineri were studied. In the former species all juveniles had a well developed stylet and pharynx, while the body of the 4th stage juveniles contained numerous dark granules and this is considered the resting stage. In P. steineri the stylet and pharynx were well developed in the 2nd and 3rd stage juvenile, but the 3rd stage juvenile had numerous granules in the body suggesting it is the resting stage. Fourth stage juveniles had no stylets and the pharynx is much reduced. Because some moulting females have the stylet cone of the juveniles being shed together with the juvenile cuticle, it is concluded that the 4th stage is short-lasting. The length of the body, pharynx, tail and genital primordium as well as the index b increases in successive developmental stages. Indices a, c, c' were almost constant in all juvenile stages. The resting juvenile stage characterises species and it should be included in species descriptions for better characterisation of Paratylenchus species. Paratylenchinae: stades de developpement de Paratylenchus straeleni (De Coninck, 1931) et P. steineri Golden, 1961 (Nematoda: Tylenchulidae) - Ont ete etudies les stades de developpement post-embryonnaire de populations sauvages de Paratylenchus straeleni et de P. steineri. Chez la premiere espece tous les juveniles ont un stylet et un pharynx bien developpes alors que le corps des juveniles de 4eme stade contient de nombreux granules fonces; ce stade a donc ete considere comme le stade de quiescence. Chez P. steineri, le stylet et le pharynx sont bien developpes chez le second et troisieme stades juveniles, mais ce dernier montre de nombreux granules a l'interieur du corps, suggerant qu'il constitue le stade de quiescence. Les juveniles de 4eme stade sont depourvus de stylet et le pharynx est tres reduit. Du fait que chez les femelles en train de muer le cone du stylet des juveniles est rejete avec la cuticule des juveniles, il a ete conclu que le 4eme stade n'a qu'une courte duree de vie. Les longueurs du corps, du pharynx, de la queue et du primordium genital de meme que l'index b augmentent en passant d'un stade a l'autre. Les indices a, c et c' sont generalement constants chez tous les stades juveniles. Le stade quiescent des juveniles est caracteristique de l'espece et devrait etre inclus dans les descriptions d'especes pour une meilleure caracterisation specifique des Paratylenchus.

Paratylenchinae: postembryonic developmental stages of Paratylenchus straeleni (De Coninck, 1931) and P. steineri Golden, 1961 (Nematoda: Tylenchulidae)

in Nematology



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