FORMATION OF AGGREGATED COLONIES IN BOUGA INVILLIA-SUPERCILIARIS (HYDROIDEA, ATHECATA)

The planulae of metagenetic hydroid Bougainvillia superciliaris (L. Ag assiz) have the gregarious type of settling and undergo metamorphosis in giant aggregations formed by two to two hundred specimens. The stol ons of aggregated colonies lie closely to each other, but do not fuse nor lose their isolation. The larval behavior is gregarious only on sm ooth surfaces. Planulae settle alone or as pairs onto sand and stones. Since the few colonies collected in the White Sea and in the Sea of J apan were described as solitary specimens, the gregarious settling cou ld be interpreted as the abnormal behavior in limited water volumes. T he planulae settle most actively onto the shells of bivalves and cirri peades, that might be an unknown until now possible habitat of the hyd roid.