The marine platyhelminth Macrostomum lignano lives in sediments of the Adriatic shores and experiences episodes of hypoxia and exposure to toxins and large temperature variations in its natural environment. The flatworm is robust and easy to maintain in coculture with its prey, the diatom Nitzschia spp. at 16:8 h light/dark cycle and 20 ± 2 °C. With a view to establishing this flatworm as physiological model for environmental stress, toxin exposure and organismic adaptations we have performed a series of live imaging techniques using established and new dyes (Rivera-Ingraham et al. 2013). Here we report the staining of M. lignano with synthetic derivatives of the sponge-derived natural product ageladine A. The new synthetic derivatives show different pH dependent excitation/ emission profiles and different staining characteristics. One compound in particular (P3) shows highly organ specific staining, staining only the rhabdites. Rivera-Ingraham GA, Bickmeyer U, Abele D. J Exp Biol. 2013 Mar 26. [Epub ahead of print]