BIOCHEMICAL AND CYTOLOGICAL BASES OF METAMORPHOSIS IN HYDRACTINIA-ECHINATA

Larvae of the marine hydroid Hydractinia echinata Fleming are induced to settle and metamorphose by contact with bacteria of the genus Alter omonas espejiana (Leitz and Wagner 1992). In previous studies the bioc hemical mechanism for the activation of the larvae was found to includ e the signal transduction pathway via the phosphatidylinositol cycle a nd a role for a kinase C-like enzyme was established. In the present i nvestigation laboratory-reared larvae were immunohistochemically stain ed with antibodies against kinase C and experiments were conducted to investigate protein phosphorylation during initial metamorphic events. A polyclonal antibody against a synthetic peptide derived from a cons erved region of kinases C binds to an antigen in neurosensory cells of the anterior part of the larvae and corresponding nerve fibres. The W estern blot reveals major binding to a protein of M(r) (relative molec ular mass) = 67 and two minor bands at M(r) = 66 and 48. Assays in viv o show that 3 to 25 min after induction of metamorphosis the phosphory lation of a protein with M(r) = 30 is enhanced. A hypothesis about the mechanism of induction at the cellular and biochemical level is prese nted which combines most of the ideas now available from our and other groups.