LAUSR

The presence of non-indigenous species outside their home range attracts growing attention by the scientific community, as well as policy makers and common citizens. However, dispersal pathways of most non-indigenous species remain poorly understood. The association between non-indigenous and indigenous species may facilitate dispersal in non-native habitats. Identifying such associations is therefore paramount, but few studies have addressed this issue to date. The present work reports the association between the non-indigenous spider crab Pyromaia tuberculata, morphologically and molecularly identified, with the autochthonous scyphomedusa Catostylus tagi in European waters. This is the first time this widespread invasive brachyuran crab is described associated with jellyfish. In the laboratory, P. tuberculata was observed feeding on the gonadal tissues of its cnidarian host, although this behaviour needs to be confirmed in the wild. The association between P. tuberculata and C. tagi raises awareness on how the dispersal potential of this non-indigenous species may be significantly enhanced. As recommended by the Marine Strategy Framework Directive, it is important to include P. tuberculata in the European monitoring programmes of non-indigenous species. Future studies should continue to investigate the prevalence of this specific association, as well as other associations between jellyfish and non-indigenous fauna, as an early warning initiative. Researchers may benefit from ongoing citizen science projects to gather data on this overlooked pathway for dispersal of non-indigenous species.