The volatile constituents of the marine sponge Ircinia felix were obtained by dynamic
headspace extraction and analyzed by HRGC, HRGC-MS and HRGC-Odor at sniffing port.
Fifty-nine volatiles were identified for the first time in the odor of this sponge.
Hydrocarbons (32.9%), alcohols (17.8%) and carbonyl compounds (16.0%) predominated
in the sponge volatile profile, followed by esters (11.6%), halogen compounds (8.6%),
ethers (7.7%), nitrogen and/or sulfur compounds (4.6%) and carboxylic acids (0.8%).
Among the identified volatiles, thiobismethane (commonly known as dimethylsulfide),
methyl isocyanide and methyl isothiocyanate were found to be responsible for the nauseating
and toxic smell emitted by the sponge and for the antimicrobial activity detected
in the volatile extract. Exudation experiments in aquarium and in situ conditions
revealed that thiobismethane, methyl isocyanide and methyl isothiocyanate are continuously
released by the sponge. Upon injury, the concentration of these volatiles increased
strongly. Hence, these substances form a chemical protective barrier which may help
these sponges avoid fouling, compete for space, prevent infection in the short term,
and/or signal generalist predators regarding the existence of other toxic substances
in the internal tissues.