THE PATTERN OF EARLY POSTEMBRYONIC DEVELOPMENT OF PARASITENGONA MITES (ACARIFORMES: PARASITENGONA) AND ITS CAUSATIVE ANALYSIS

About author:

Shatrov A. B., Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, 199034, St-Petersburg, Russia

Acknowledgments:

This investigation is supported by the grant № 97-04-48977 from the Russian Foundation for Fundamental Researches.

Annotation:

An analysis of the complex ontogenesis of Parasitengona mites with a special regard to its early stages is given from the posit ion of the comparative morphology and the ecophysiology. Quiescent regressive prelarva is a special instar retained in ontogenesis for the purpose of the utilization of the embryonic yolk. However, it provides formation of small sixlegged larva only. Since the prelarva expresses the process of postembryonic morpho-genesis and, moreover, has its own cuticle closely applied to hypodermis, it must be considered as an individual instar of the postembryonic development although it is situated in part or entirely within the egg-shell as a particular pharate stage. Correspondingly, changing of prelarval cuticle to larval one can not be considered as a true embryonic moult. Larva feeds intensively by means of parasitism on vertebrate and invertebrate hosts, with the strategic aim to reach relatively large sizes of the conservative postlarval instars (deutonymph and adult) living freely in soil and litter or in water milieu. The excessive feeding of larva provides immobolization and regression of the first nymphal instar. A synchronous regression of the protonymph and the tritonymph reveals high degree of morphogenetic correlations in the ontogenesis in this group of mites.

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