Chemical antifouling defences of sea stars: effects of the natural products hexadecanoic acid, cholesterol, lathosterol and sitosterol

Abstract

The role of natural products in keeping the surfaces of the sea stars Linckia laevigata, Fromia indica, Cryptasterina pentagona and Archaster typicus free of fouling organisms was investigated. Conditioned seawater of these sea stars did not have any effects on the settlement of the ecologically relevant diatoms Amphora sp. and Nitzschia closterium and the bryozoan Bugula neritina. However, dichloromethane, methanol and aqueous extracts of whole sea stars at 100, 10, 1 and 0.1 µg cm -2 had concentration-dependent effects on the settlement of these fouling species and the polychaete Hydroides elegans. Based on bioassay-guided fractionation and analysis with proton nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry (GC-MS), the most bioactive fractions contained several fatty acids and sterols. To determine whether the compounds responsible for the observed antifouling effects were present on the surface of all 4 sea star species, surface-associated compounds were tested against Amphora sp., N. closterium, B. neritina and H. elegans. These compounds reduced the settlement of at least 2 of the 4 fouling species for each sea star species. Using surface extractions and GC-MS analysis, the most abundant surface-associated fatty acids and sterols of each sea star species were identified and quantified. Hexadecanoic acid, cholesterol, lathosterol and sitosterol were tested at surface-associated concentrations, ranging from 1000 to 1 ng cm -2 , in settlement assays. Whereas the settlement of B. neritina was not affected by any of the compounds, hexadecanoic acid, cholesterol and lathosterol significantly reduced the settlement of N. closterium at surface-associated concentrations.

Marine natural products

“…836 MS/MS techniques were used to investigate the saponin chemistry of the body and Cuvierian tubules of a Mediterranean collection of Holothuria forskali. 838 This journal is ª The Royal Society of Chemistry 2011 Structures for a number of novel metabolites were proposed, but based solely on MS/MS data.…”

Responses of the estuarine copepod Pseudodiaptomus annandalei to diatom polyunsaturated aldehydes: Reproduction, survival and postembryonic development

“…However, in the last two decades, mounting evidence is accumulating on the detrimental effects of diatoms on primary consumers (Miralto et al, 1999;Adolph et al, 2004;Ianora et al, 2004;Carotenuto et al, 2005;Guenther et al, 2009;Romano et al, 2010). The detrimental effects of diatoms are generally attributed to the release of secondary metabolites such as polyunsaturated aldehydes and other metabolites deriving from the oxidation of fatty acids (collectively termed oxylipins) after cell damage as occurs during copepod feeding (reviewed by Caldwell, 2009;Ianora and Miralto, 2010) or lysed from senescent cells during bloom periods (Vidoudez et al, 2011).…”

Toxic Diatom Aldehydes Affect Defence Gene Networks in Sea Urchins

“…Several studies, however, have shown that some diatom species produce secondary metabolites, collectively termed oxylipins (e.g. polyunsaturated aldehydes or PUAs) and other products, deriving from the oxidation of fatty acids with negative effects on copepods [ 5 , 6 ], cladocerans [ 7 ], sea urchins [ 8 ], sea stars [ 9 , 10 ], polychaete worms and ascidians [ 11 , 12 ]. The first molecular studies on the effects of PUAs on the sea urchin, Paracentrotus lividus , were reported only very recently [ 13 – 15 ].…”