Meeting Abstract

96.3  Sunday, Jan. 6  Regulation of metamorphosis in Hydroides elegans: not what we thought NEDVED, B.T.*; WILLSEY, E.D.; COURY, R.; HADFIELD, M.G.; Kewalo Marine Laboratory, Uni. of Hawaii; University of Toronto; Kewalo Marine Laboratory, Uni. of Hawaii; Kewalo Marine Laboratory, Uni. of Hawaii nedved@hawaii.edu

Larvae of the serpulid polychaete Hydroides elegans require contact of their episphere with specific bacterial substrata to initiate metamorphosis. While apical sensory organs (ASO) have long been thought to bear receptors for metamorphic cues, we have recently shown that laser-ablation of the ASO in these larvae does not inhibit metamorphosis. To investigate alternate sites of this chemoreception, we used immunohistochemistry and pharmacological assays to determine if cells expressing catecholamines or nitric oxide (NO) are necessary for the induction of metamorphosis. Antibodies raised against tyrsosine hydroxylase, an enzyme required for catecholamine biosynthesis, labeled numerous sensory cells within the larval episphere. One or two hr exogenous pulses of the catecholamines dopamine (DA), noradrenalin (NA) and adrenalin (AD) induced larvae of H. elegans to metamorphose in the absence of biofilms. Because AD is synthesized from both DA and NA, it may be used to transmit inductive cues within the central nervous system of H. elegans. Consistent with these data, antagonists to α-adreno-receptors inhibited metamorphosis. Contrary to the responses of other invertebrate larvae, application of agents that act as NO synthase inhibitors, NO scavengers, and NO donors had no effect on metamorphosis, suggesting that NO may not play a role in regulating metamorphosis in H. elegans. Taken together, these data suggest that, within Lophotrochozoans, there is evolutionary plasticity in the detection of metamorphic triggers, transmission of inductive cues, and the responses of target tissues to metamorphic signals.