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The external features of the embryo of the dipluran, Lepidocampa weberi Oudemans are described. The long germ band is formed, and blastokinesis is a simple flexion of the germ band. The primary dorsal organ is formed between the cephalic and abdominal ends by concentration of serosal cells. The mouth fold is formed by ventral extension of the intercalary, mandibular, and maxillary terga, through which entognathy is completed. The posteroventral region of the mouth fold develops into the admentum. Rotation of the labial anlagen is involved in labial formation, and the glossa, paraglossa, and labial palp acquire a tandem arrangement. The postmentum is formed by fusion of the labial subcoxae and is appendicular in origin. The styli and exertile vesicles are derived from the distal parts of bifurcated appendicular anlagen of the second to seventh abdominal segments. The columnar appendage of the first abdominal segment is serially homologous with the exertile vesicles of the following segments. The abdomen is composed of ten segments, and the cercus is the appendage of the tenth, last abdominal segment. Embryogenesis of Lepidocampa weberi resembles that of the rhabduran Campodea staphylinus (Uzel, 1898) as well as that of the dicelluratan Japyx major (Silvestri, '33). It may be emphasized that the rhabduran and dicelluratan diplurans share important features such as entognathy formation and abdominal organization, and the resemblance between them seems to be close enough to postulate their close affinity. Some embryogenetic features, which Diplura and Collembola share, are recognized as plesiomorphic and the manner of entognathy formation may significantly differ. J. Morphol. 237:101-115, 1998. © 1998 Wiley-Liss, Inc. |
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