###### Abstract  
Solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) was employed for the headspace determination of the volatile organic fraction emitted by two of the most common Mediterranean demosponges, _Ircinia variabilis_ and _Sacrotagus spinosus_, and of indole and some biogenic amines released by sponges in an aqueous medium. A total of 50/30 \(\upmu\)m divinylbenzene/carboxen/polydimethylsiloxane and 75 \(\upmu\)m carboxen/polydimethylsiloxane fibers were used for the headspace extraction of low molecular weight sulfur compounds from a hermtically sealed vial containing sponge fragments, while the direct immersion determination of indole and biogenic amines was performed. The biogenic amines were extracted after in-solution derivatization with isobutyl chloroform. All analytical parameters (linearity, limits of detection, and quantification, precision, and recovery) were evaluated for indole and biogenic amines. SPME-GC-MS proved to be a reliable means of highlighting the differences between molecules released by different sponges, principally responsible for their smell. The combined approaches allowed the identification of several volatile compounds in the headspace and other molecules released by the sponges in an aqueous medium, including indole and the BAs cadaverine, histamine, isobutylamine, isopentylamine, propylamine, 2-phenylethylamine, putrescine and tryptamine. The results obtained represent a further contribution to the picture of odoriferous molecules secreted by sponges. VOCs; indole; biogenic amines; Mediterranean Irciniidae; SPME-GC-MS +
Footnote †: journal: _Journal of the American Journal of Physics_  
0000-0001-8000-0000-0000-0000-00000-0000-0000-0000-0000-0000-0000-00000-00000-00000-00000-00000-00000-00000-00000-00000-000000-00000-00000-0  
The so-called \"horny sponges\" belonging to the order Dictyoceratida (Class Demospongiae, Subclass Keratosa), widespread and rather abundant on Mediterranean bottoms, are currently considered the most productive, since they have contributed over 20% of newly discovered sponge-derived bioactive compounds [8]. These compounds are very diverse in both structure and bioactivity, with terpen representing 73% of the reported chemicals, followed by nitrogenous compounds (13%). Specifically, the family Irciniidae, with the three genera _Ircinia_, _Psammocinia_, and _Sarotagus_, provided 35 new compounds, mainly showing antibacterial and cytotoxic activity, in the 2013-2019 period alone [9]. The Irciniidae, like other species of sponges, are characterized by an unpleasant odor, clearly perceptible when exposed to the air and even more intense when they are cut. The manipulation of different species of Keratosa during in situ sponge culture experiences [10; 11; 12; 13; 14] allowed researchers to perceive the odor released by the sponges and to detect the effect on researchers, due to inhalation or contact with the specimens. Effects such as nausea, headache and skin rashes have sparked our interests in the search for volatile compounds responsible for odor in sponges, bearing in mind their possible biological role. To the best of our knowledge, little research has been carried out to characterize the volatile chemicals produced by marine sponges [15; 16; 17; 18], and those also perceptible in water, whether they are hydrophilic or hydrophobic molecules [19; 20], bearing in mind their possible role in the communication within the holoboint and in the defense against external organisms. As regards the genus _Ircinia_, [PERSON] et al. [17] and [PERSON] et al. [21] focused on Caribbean species, whereas information on some Irciniidae collected from the Western Mediterranean is available in the grey literature [22]. Among nitrogenous compounds, indole is characterized by a typical fecal odor. It is originated from the amino acid tryptophan by the action of bacteria and is involved in various aspects of bacterial life [23].