Meeting Abstract

P1.102  Jan. 4  Regulation of Settlement and Metamorphosis of Metatrochophore Larvae of the Polychaete Annelid Capitella sp. I by Nitric Oxide and G-proteins BREWER, Theresa*; PATEL, Priyam; PECHENIK, Jan/A; LAUFER, Hans; BIGGERS, William/J; Wilkes University; Wilkes University; Tufts University; Univeristy of Connecticut; Wilkes University theresa.brewer@wilkes.edu

G-proteins and nitric oxide (NO) are involved in the metamorphosis of invertebrates as diverse as gastropods, sea urchins, ascidians, and insects. We sought to determine if G-proteins and nitric oxide signaling are also involved in regulating settlement and metamorphosis of the opportunistic polychaete annelid Capitella sp. I. Nitric oxide was detected in Capitella larvae using the fluorogenic substrate 4,5-diaminofluorescein diacetate (DAF-2DA). In support of a functional role for NO in metamorphosis of this species, settlement and metamorphosis was successfully induced by treatment with two inhibitors of the inducible isoform of nitric oxide synthase (iNOS), aminoguanidine hemisulfate (AGH) and S-methylisothiourea sulfate (SMIS), in a concentration-dependent manner. Settlement and metamorphosis was not, however, induced by G-nitro-L-arginine methyl ester (L-NAME), an inhibitor of constitutively produced forms of nitric oxide synthase. We also found that spontaneous settlement and metamorphosis of Capitella larvae, which occurs eventually in the absence of a chemical cue, was inhibited by the G-protein inhibitor guanosine 5′[&beta-thio]diphosphate (GDP-&beta-S). Our results suggest that a form of NOS similar to that of iNOS inhibits larval settlement of Capitella sp. I. We are now exploring the possibility that NO may inhibit settlement of these larvae through the activation of guanylate cyclase and inhibition of a G-protein coupled receptor whose activation is required for settlement and metamorphosis.