TABLE CONTENTS

Tardigrade-nematode Interaction: Predator and Prey Behaviour and their
Impact on Feeding Rates and Prey Numbers
Hohberg, K. (1), J.M. Jeschke (2) &W. Traunspurger (3)
(1) State Museum of Natural History Görlitz, Germany; (2) Ludwig-Maximilian-University München, Germany
& Cary Institute of Ecosystem Studies, Millbrook, USA; (3) University Bielefeld, Germany
Many predators prey on nematodes, but little is known about the strength of these predatorprey
interactions and the regulatory top-down influence on nematode species composition
and population growth. In order to provide insights into the structuring forces of predator –
nematode interaction, we studied a tardigrade (Macrobiotus richtersi) - nematode (Pelodera
teres, Acrobeloides nanus) system in detail, quantifying feeding rates, environmental
influences and the importance of predator and prey behaviour. Intensive laboratory and
microcosm investigations revealed that the tardigrade is an efficient predator of nematodes, a
single adult consuming up to 104 juvenile nematodes in four hours. Tardigrade feeding rates
were influenced by body sizes of predator and prey, nematode densities, temperature,
substrate type and environmental richness. Additionally, specific behaviour of both, predator
and prey, affected consumption rates and prey numbers: 1) Food-rich conditions as well as
satiation led to wasteful feeding, i.e. low exploitation of single prey item. As a consequence,
for the same biomass uptake tardigrades reduced prey numbers up to three times as much as
under food-poor conditions. 2) Vigorous defence behaviour of the prey Pelodera teres
reduced feeding-rates, but on the other hand it increased the number of nematodes that were
killed by the tardigrade. In order to correctly interpret predator-prey interaction in the field
and to assess the actual reduction in prey numbers caused by a predator, it is therefore
decisive to consider animal behaviour as well as environmental factors.
5 th International Congress of Nematology, 2008 106