Happy together? Avoidance of conspecifics by gregarious mussels.

摘要: Zebra mussel Dreissena polymorpha is a Ponto-Caspian species invasive in Europe and North America, with great environmental impact. It lives byssally attached to hard substrata large aggregations, which often explained by its preferences for conspecifics, though direct evidence such has been rather limited so far. We studied the reactions of zebra mussels hypothesizing that they may either be attracted one another or form aggregations only absence alternative attachment sites. In Experiment 1, we tested tendency detach from existing druses depending on druse size (2-25 individuals) substratum type (soft: sand; hard: glass). Mussels detached significantly more larger compared soft smaller druses, respectively. This indicates tended avoid conspecifics at high density, particularly when was available. 2, responses single distant (3 15 cm) (0, 3, 15 individuals per 2.5 l tank) sandy substratum. The presence regardless their distance resulted unattached staying initial positions. did not move preferentially towards away conspecifics. Thus, even unsuitable were probably exhibited an avoidance reaction reducing movement. suggests dense are formed due lack available sites than