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Abstract:
In modern developmental biology a number of animals are used as model organisms. Among these are the fish Danio rerio (Actinopterygii: Cyprinidae), the fruitfly Drosophila melanogaster (Diptera: Drosophilidae) and the nematodes Caenorhabditis elegans (Nemat- oda: Rhabditidae) and Pristionchus pacificus (Nematoda: Diplogastridae). Although these animals have been kept in the laboratories for years and examinedin detail very little is known about their biology and ecology in the field. Pristionchus species so far were only found in randomly taken soil samples and occasion- ally on beetles. We intend to expand the knowledge about the model organism Pristionchus pacificus and the whole genus Pristionchus and learn more about their distribution and bio- logy. Using recent indications of an association between nematodes and certain beetles we screened several beetle species for nematodes. Adults and larvae of the beetles were col- lected, dissected, and placed on agar plates with Escherichia coli as food source. After two to three days the first worms appeared. The nematodes were determined morphologically and by using molecular methods (sequencing part of the small subunit of the ribosomal RNA). In some beetle populations up to 90% of the collected individuals were infested with Diplo- gastrid nematodes . Others seemed to be nematode free. On certain beetles up to three dif- ferent nematode species belonging to two genera (Diplogasteroides und Pristionchus) could be detected. The nematodes appeared in a distinct succession. In the survey we could detect four genera of diplogastrid nematodes on Scarab beetles and their larvae living in soil or rotten wood. Within the genus Pristionchus we isolated three out of six laboratory species while another new Pristionchus species was detected on the stag beetle Lucanus cervus.
