Nitric Oxide-Serotonin interplay in the cyprid metamorphosis of Balanus amphitrite (Cirripedia, Thoracica)

Nitric Oxide (NO) signaling is known to govern the cyprid metamorphosis of barnacle Balanus amphitrite, a potential biofouling organism. This signaling cascade is mainly driven by two important enzymes, Nitric Oxide Synthase (NOS) and cyclic Guanosine monophosphate (cGMP)-specific Phosphodiesterase (PDE), which exist in multiple isoforms. But, involvement of the exact isoform of these enzymes was unknown, and the same was addressed in the present study using pharmacological compounds, targeting the specific isoforms of NOS and PDE. When the cyprids were treated with specific NOS inhibitors (7-Nitroindazole for NOS I and S-methylisothiourea hemisulphate for NOS II), the metamorphosis was promoted indicating the involvement of both NOS I and NOS II. However, when cyprids were exposed to PDE inhibitors (Sildenafil, Dipyridamole and Bay 73-6691 targeting PDE5, PDE6 and PDE9 respectively), metamorphosis was significantly inhibited only in case of Sildenafil, indicating the involvement of PDE5. The expression of PDE5 in the cyprid was demonstrated using immunofluorescence technique. Further, it was also demonstrated that the interplay between NO and Serotonin signaling plays a vital role in the pelago-benthic transition of B. amphitrite. Targeting these signaling pathways in the future could provide an antifouling solution against barnacles.