The general life cycle of fresh water mites (Hydrachnelliae, Acari)
1976 - Volume: 18 Issue: 3 pages: 496-502
Hydrachnellae: Life cycle
l) This paper deals with the possibility of representing in general form the life cycle of the Hydrachnellae and of defining clearly the individual ontogenetic steps. In this sense the nomenclature of HENIING (1882) is compared with that of GRANDJEAN (1932). 2) Henking’s nomenclature should be given up. It is presently understood only by the few specialists in the Hydrachnellae, and even among these specialists there have repeatedly been misunderstandings with the definition of some of HENKING s stages. 3) To achieve a general understanding in the field of Acarology, the nomenclature of Grandjean should be adopted and the six developmental steps following the egg in Hydrachnellae should be designated prelarva - larva - protonymph - deutonymph - tritonymph - adult. 4) According to Grnadjean the individual developmental steps (also called ’stases’ or ’stages’) are characterised by unique morphology and delimited in time by a moult at the beginning and the end. With the Hydrachnellae, there arises a problem from the fact that two moults are missing; the protonymph does not emerge from the cuticle of the larva and the tritonymph does not emerge from the cuticle of the deutonymph. Because of this, the time of transition to proto- and tritonymph is taken as being when the larval and deutonymphal cuticles respectively become non-functional and can be removed without hindering the further development. This point in time can only be precisely determined by preparations of a whole series of animais, and is therefore impossible if one only has a little living material, as this should be used in biological studies for rearing to the adult stage. In these cases the life cycle of the Hydrachnellae can only be characterised according to phases of activity and inactivity. The inactive larval phase is included with the protonymph stase as ’postlarval resting stage I’ and the inactive deutonymph phase with the tritonymph stase as ’postlarval resting stage II’. Starting with the egg, there is then the series: prelarva - larva (active phase) - postlarval resting stage I - deutonymph (active phase) - postlarval resting stage II - adult.
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