Induction of metamorphosis by bacteria and by a lithium-pulse in the larvae ofHydractinia echinata (Hydrozoa)

The planulae ofHydractinia, the metamorphosis of which normally is induced by certain bacteria, will undergo transformation into polyps also when exposed to a lithiumpulse. The optimal concentration and incubation period for rapid and complete transformation have been determined at 24 mM Li⁺ and 2 hrs respectively. 96 mM K⁺ applied for 2 hrs will also result in some induction. The possible mode of action exerted by the Li-ion as compared with induction caused by bacteria is discussed.