Polyunsaturated aldehydes released by marine planktonic diatoms upon wounding have been extensively studied since the discovery that they reduce the hatching success of copepods. Diatoms are also abundant in benthic marine ecosystems. For this reason we investigated the presence and the possible ecological roles of Cocconeis scutellum parva, a diatom found tightly attached to the leaves of Posidonia oceanica. This diatom was previously demonstrated to play an important trophic role for the shrimp Hippolyte inermis, by influencing its sex reversal. In the present study, C. scutellum parva was isolated and cultivated and the volatile compounds released upon cell disintegration were identified by mass-spectrometric methods. We demonstrated the presence of unsaturated aldehydes with chain lengths from C 5 to C 10 . Unexpectedly, we found C 6 compounds represented by 3(Z)-hexenal, 2(E)-hexenal, hexanal and hexanol-1 that resemble the typical bouquet observed in higher plants. Compounds not described before for diatoms were, among others, pentane-2, 3-dione and octane-2, 3-dione. Food choice experiments performed on 17 animal species associated with P. oceanica meadows indicated that these grazers recognise the presence of the odour compounds, exhibiting complex patterns of reactions according to their life strategies. The mosaic of results obtained at various concentrations, in different species, indicated that wound-activated infochemicals generate a web of communication among diatoms and benthic invertebrates.KEY WORDS: Infochemical · Odour · Seagrass · Behaviour · Feeding · Wounding · Diatom
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 400: [63][64][65][66][67][68][69][70][71][72][73] 2010 compound (whose structure has not yet been identified; Nappo et al. 2009) present in these diatoms acts as a spring signal for the production of young females, probably due to a long co-evolutionary process .In other cases, secondary metabolites produce deleterious effects on consumers. Compounds responsible for the biological effects have been demonstrated to be volatile organic compounds (VOC) not present in intact cells but released by a lipoxygenase cascade upon cell wounding (Pohnert 2000, Jüttner 2005. Unsaturated aldehydes of the lipoxygenase cascade in planktonic diatoms exhibit teratogenic effects on copepod larvae and reduce the viability of their eggs (Miralto et al. 1999). Wound-activated diatom cells also release unsaturated aldehydes (Pohnert 2002) that are inhibitors of mitotic proliferation in sea urchin embryos (Miralto et al. 1999). Similar relationships, although less striking, were demonstrated between the crustacean Daphnia pulicaria and some freshwater diatoms (Carotenuto et al. 2005).Secondary metabolites produced by the lipoxygenase pathway may also act as repellents against grazers ( Fink et al. 2006). The lipoxygenase product 2(E), 4(E),7(Z)-decatrienal has been shown to act as a repellent for freshwater crustacean grazers (Jüttner 2005). T...
Cocconeis scutellum is a benthic diatom producing one or more compounds responsible for the early programmed cell death (apoptosis) of the male gonad and the androgenic gland of the protandric shrimp Hippolyte inermis Leach. The metabolite composition of both the ether and butanol extracts was studied by gas chromatography-mass spectrometry (GC-MS) in both electron impact (EI) and chemical ionization (CI) mode. The compounds were identified as trimethylsilyl (TMSi) derivatives. The structure of the fatty acids (FA) was confirmed after conversion to their methyl esters. The ether fraction of C. scutellum contained FA (76%), of which 30% were saturated (SFA), 24% monounsaturated (MUFA) and 22% polyunsaturated (PUFA). Mono-(8%) and diglycerides (3%) as well as sterols (5%) and isoprenoid compounds (4%) were also found in this fraction. The butanol extract consisted of FA (45%), carbohydrates (25%), amino acids and N-containing metabolites (10%), fatty alcohols (9%), glycerides (4%) and organic acids (3%). In the literature, many reports deal with the chemistry and the chemical ecology of planktonic diatoms; contrastingly, benthic species are still less studied, especially with respect to their chemical composition, due to their difficult cultivation. Hence, our investigation represents a preliminary approach to clarify on chemical bases the ecological role of Cocconeis on decapods in the marine benthos, as well as a description of the metabolic pattern of this benthic diatom.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.