Resistance to flooding of different species of terrestrial oribatid mites (Acari, Oribatida)

Abstract

Resistance to flooding was tested in six terrestrial oribatid mite species with different ecological needs. The silvicolous Galumna lanceata and Oppiella (Oppiella) marginedentata showed low average survival times of seven and 14 days, the moss-dwelling Zygoribatula exilis tolerated a month of submergence on average, the eurytopic Eueremaeus oblongus and Tectocepheus velatus sarekensis survived an average period of 52 and 80 days and the euryoecious Plathynothrus peltifer showed the highest tolerance with 130 days median lethal time. Accordingly, overflow tolerances are clearly species dependent, but may also be correlated with the ecological needs of each species. Most of the inferred survival times clearly exceed the periods of naturally occurring flooding in typical terrestrial temperate habitats. Therefore, terrestrial oribatid mites may show a basic predisposition for overflow tolerances. We also performed the opposite experiment, i.e. we exposed the aquatic Hydrozetes lemnae permanently to atmospheric air. More than half of the individuals survived 130 days but all tested specimens completely reduced activity which indicates that H. lemnae initiates a state of dormancy when being outside of water, probably to withstand longer lasting droughts in nature.

Keywords

• plastron
• larviparity
• survival time
• aquatic
• fresh water