AUTHOR=Clark Kasey E. , Capper Angela , Liu Wei-Ting , Fenner Amanda M. , Almanza Alejandro , Della Togna Gina , Herrera Liuris , Johns Timothy , Paul Valerie J. , Dorrestein Pieter C. , Capson Todd L. , Balunas Marcy J. 

TITLE=Sequestration and Cyanobacterial Diet Preferences in the Opisthobranch Molluscs Dolabrifera nicaraguana and Stylocheilus rickettsi

JOURNAL=Frontiers in Marine Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.766282

DOI=10.3389/fmars.2021.766282

ISSN=2296-7745

ABSTRACT=<p>A multidisciplinary approach was used to assess chemical ecological dietary interactions between marine organisms as a tool to isolate novel ecologically relevant compounds with biotechnological potential. First, laboratory-based feeding preference assays of the sea hare <italic>Dolabrifera nicaraguana</italic> (previously known as <italic>D. dolabrifera</italic>), an anaspidean mollusc, were conducted by simultaneously offering six food options collected from nearby tidal pools in the Coiba National Park in the Tropical Eastern Pacific of Panama. An evaluation of preferred dietary repertoire revealed <italic>D. nicaraguana</italic> significantly preferred cf. <italic>Lyngbya</italic> sp. over the cyanobacterium <italic>Symploca</italic> sp., green alga <italic>Chaetomorpha</italic> sp., and red alga <italic>Spyridia</italic> sp. A no-choice feeding assay using cf. <italic>Lyngbya</italic> sp. or green alga <italic>Cladophora</italic> sp. supported this finding. Secondly, we conducted bioactivity-guided fractionation using the preferred food source of <italic>D. nicaraguana</italic>, the ‘hair-like” cf. <italic>Lyngbya</italic> sp. from which we also isolated and elucidated two new depsipeptide compounds, veraguamide M (<bold>1</bold>) and veraguamide N (<bold>2</bold>). Veraguamides M (<bold>1</bold>) and N (<bold>2</bold>) showed <italic>in vitro</italic> activity toward the malaria-causing parasite <italic>Plasmodium falciparum</italic> with GI<sub>50</sub> values of 4.2 and 4.3 μM, respectively, and therapeutic windows of 7.0–8.0 (based on moderate cytotoxicities to mammalian Vero cells with GI<sub>50</sub> values of 29.3 and 34.1 μM, respectively). Veraguamide N (<bold>2</bold>) was also active against <italic>Leishmania donovani</italic>, the causative agent of visceral leishmaniasis, with a GI<sub>50</sub> value of 6.9 μM. We then evaluated sequestration of these new compounds by <italic>D. nicaraguana</italic> used in the feeding assays and found trace amounts of the dietary sequestered compounds. Finally, we evaluated sequestration of these new compounds by the sea hare <italic>Stylocheilus rickettsi</italic> (previously known as <italic>S. striatus</italic>) that were grazing on the cf. <italic>Lyngbya</italic> sp. used in the feeding assays and found both to be sequestered. This study is the first example whereby compounds with significant activity against tropical parasites have been found in both the sea hare <italic>S. rickettsi</italic> and its cyanobacterial food source. These results suggest that chemical ecological studies involving sea hares and cyanobacteria continue to provide a diverse source of bioactive compounds with biotechnological potential.</p>