Systematic status of Hydrozetes octosetosus Willmann, 1932 (Acari: Oribatida: Hydrozetidae) in the light of ontogenetic and ecological studies

Abstract

The systematic status of Hydrozetes octosetosus was investigated by comparing this species to H. lacustris, which is the type species for the genus Hydrozetes Berlese, 1902. These species are similar, but probably not synonyms as recently proposed. They differ mainly by the position of notogastral seta lm in the adult and position and length of this seta and total number of long setae in the posterior part of nymphs. In the adult of H. octosetosus, this seta inserts behind the opisthosomal gland opening (gla), but in front of it in H. lacustris. In the nymphs of H. octosetosus seta lm inserts behind gla opening, but medially to it in H. lacustris. In H. octosetosus this seta is very long and the total number of long setae in nymphs is four pairs, while in H. lacustris seta lm is short and the total number of long setae in nymphs is three pairs.

Keywords:

• Acari
• aquatic mites
• Hydrozetes octosetosus
• juvenile stages
• ontogeny
• oribatid mites
• setation

Acknowledgements

We cordially thank Prof. Dr Roy A. Norton, State University of New York, Syracuse, USA, for his thorough review of this manuscript and many valuable suggestions. Cathy Jenks, Department of Biology, University of Bergen, Norway, is acknowledged for linguistic improvements of the last version of the manuscript.