ZOHLKE, R. & BLOME, D. & VAN BERNEM, K. H. & DITTMANN, S. (1998): Effects of the tube building polychaete Lanice conchilega (PALLAS) on benthic macrofauna and nematodes in an intertidal sandflat. -Senckenbergiana marit., 29 (1/6): 131-138, 4 figs., 2 tabs.; Frankfurt a. M.] Biogenic habitat structures playa major role for distribution pattems of benthic fauna. Tube-dwelling polychaetes provide one of the main features in the otherwise re[atively low structured sandy intertidal. The airn ofthis study was to investigate the effect of the tube-dwel[ing sand-mason Lanfce conchilega on macrofauna and nematodes in an intertidal sandflat in the Wadden Sea area offthe German coast. Field smdies and experiments were carried out on the associated macrobenthic fauna of natural L. concbilega aggregates and of artificial tubes. Furthermore, the distribution of nematode species at increasing distances along transects arising from individual L. conchilega mbes, was investigated.Natural as well as artificial tubes had positive effects on numbers of macrofaunal species and individuals. Yet, juvenile Mya arenaria were the only species appearing in higher numbers in both L. conchilega aggregates and artificial tube fields. They used the tube structure to attach themselves with their byssus threads. The polychaete Malmgrenidla lunulata only occurred in natural L. conchilega aggregates and was ofien found inside the polychaetes' tubes. It is possibly a commensal associated to L. conchilega. In artificial mbe fiel&, opportunistic spionids and Capitella capitata settled in higher numbers. This might be due to colonisation ofsediment accumulating in the tube fiel&, utilisation of the tubes as an attachment sufface or refuge from predation. However, two predatory polychaetes, Eteone Ionga and Nereis diversicolor, were also found in higher abundance in natural or artificial tube fields.Nematode abundances were considerably higher next to ~ndividual L. conchilega tubes ata distance of 0.5 cm. This distribution was mainly caused by a group ofthreadlike species with a thin cuticle, which are thought to be adapted to epidermal uptake of dissolved organic matter.Ir is suggested that there might be a linkage between predatory polychaetes and the distribution partero found for nematodes around the tubes ofL. concbilega.

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This is the first of a series describing new turbellarian and nematode species collected during March and April 1992, on eulittoral sandy shores of Southern Queensland and northern New South Wales, Australia. The environment and all sampling sites are described. Four new species of Macrostomida (Dunwlchia arenosa, gen. et sp. nov., Bradburia australiensis, gen. et sp. nov., Macrostomum australiense, sp. nov., and Macrostomum sp. based only on female sexual maturity) were found in eulittoral habitats of sandy beaches, flats and brackish-water creeks.

Three new species of the desmodoroid genus Onyx are described from ocean beaches of northern New South Wales, Australia: Onyx macramphis, sp, nov., Onyx adenophorus, sp. nov., and Onyx cannoni, sp. nov. The genus Onyx is revised, the status of the type species, O. perfectus Cobb, 1891, is discussed and an annotated list of the species of the genus is presented. The precaudal position of the caudal glands in O. adenophoius prompts a discussion of the significance of the precaudal position of caudal glands in free-living marine nematode taxonomy in general.

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