*2.5. Fatty Acids*

GC–MS analyses allowed us to determine around thirty fatty acid methyl esters (FAMEs), ranging from methyl hexanoate to methyl tetracosanoate, in dried samples from *P. noctiluca* (Table 1). With some exception, probably due to amounts below the detection limit, these FAMEs were common to each sample group, namely bells and oral arms of female and male specimens.

From a quantitative point of view, the main fatty acid classes varied depending on specimens' body part rather than sex. In fact, saturated fatty acids (SFAs), representing 70% ca. in bells and 65% ca. in oral arms, respectively; monounsaturated fatty acids (MUFAs), accounting for 15% ca. in all samples (*p* > 0.05); and polyunsaturated fatty acids (PUFAs), constituting 14% ca. in bells and 19% ca. in oral arms (*p* < 0.05). Only slight and nonstatistically significant differences (*p* > 0.05) could be attributed to the specimen's sex. For example, SFAs were slightly more abundant in male than female bells (70.6 vs. 69.5%, *p* > 0.05); MUFAs were slightly higher in female than male oral arms (15.8 vs. 14.6%, *p* > 0.05); and PUFAs content was slightly lower in male than female bells (13.8 vs. 15.4%, *p* > 0.05) and female than male oral arms (18.4 vs. 19.2%, *p* > 0.05).

It was not possible drawing conclusions on the distribution of single fatty acids according the organism's anatomical part or sex. The only exception was represented by PUFAs of the ω6 and ω3 series, which showed to be constantly more abundant in oral arms than bells, regardless of the sex (Table 1). However, fatty acid fingerprints pointed out, as predominant components of the mauve stinger, lauric acid (3.16–4.69%), palmitic acid (32.87–36.46%), stearic acid (19.01–25.25%), arachidic acid (2.24–3.09%), lignoceric acid (1.11–1.95%), palmitoleic acid (0.61–2.38%), oleic acid (12.26–12.95%), linoleic acid (1.25–1.68%), arachidonic acid (4.23–6.67%), eicosapentaenoic acid (EPA, 4.96–6.40%), and docosahexaenoic acid (DHA, 2.36–4.02%). As can be seen in Table 1, the ω6/ω3 ratios determined in all samples were close to 1:1 (Table 1).


**Table 1.** Fatty acid methyl esters determined in the bells and oral arms of female and male specimens from *Pelagia noctiluca*. Data are reported on a dw basis, as average Gas Chromatography-flame ionization detector ( GC-FID) peak area percent ± standard deviation (*n* = 3).

a–c: Different superscript letters in the same row indicate significantly different values (*p* < 0.05 by post hoc Tukey's HSD test). Same superscript letters in the same row indicate not significantly different values (*p* > 0.05 by post hoc Tukey's HSD test).

### *2.6. Major and Trace Element Profiles*

The contents of four major elements (Na, Mg, K, and Ca), five essential trace elements (Fe, Cu, Zn, Mn, and Se), and five nonessential/potentially toxic trace elements (Cr, Ni, As, Cd, and Pb), were evaluated by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in male and female jellyfish bells and oral arms, on a dw basis (Table 2).


**Table 2.** Elemental signatures of male and female jellyfishes' bell and oral arms revealed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Contents of major elements (mg 100 g<sup>−</sup>1) and trace elements (μg 100 g<sup>−</sup>1) are expressed as mean ± SD (*n* = 3) on a dw basis.

a–c: Different superscript letters in the same row indicate significantly different values (*p* < 0.05 by post hoc Tukey's HSD test). Same superscript letters in the same row indicate not significantly different values (*p* > 0.05 by post hoc Tukey's HSD test).

Table S5 reports data of the validation procedure carried out by means of reference standards. The ICP-MS method showed good linearity for all the elements, with coefficients of correlation between 0.994 and 0.999. Acceptable recoveries between 93.49% (Ni) and 103.31% (Cr) were obtained. Evaluated in terms of RSD%, precision (intraday repeatability) and intermediate precision (interday repeatability), resulted to be within the range of 2.02 to 6.53%, and below 8.52%, respectively.

Major element signatures varied most in dependence of the organ rather than sex (Table 2). Overall, these metals appeared to bioaccumulate mainly in bells than the respective oral arms (*p* < 0.05) by the decreasing order of Na > Mg > Ca ≈ K, regardless of female and male sex (*p* > 0.05). As a result, Na was characterized by the highest levels (6544–8079 mg 100 g<sup>−</sup><sup>1</sup> for bells; 3877–3740 mg 100 g<sup>−</sup><sup>1</sup> for oral arms); while K was the less abundant one, showing contents inferior by one order of magnitude (196–229 mg 100 g<sup>−</sup><sup>1</sup> for bells; 126–143 mg 100 g<sup>−</sup><sup>1</sup> for oral arms) (Table 2).

Dealing with essential trace elements, they were found in the decreasing order of Fe > Cu > Zn > Mn > Se, in both male and female bells and oral arms. Fe was characterized by a behavior similar to major elements, since it was more abundant in bells (1309–1465 μg 100 g<sup>−</sup>1) than oral arms (854–1085 μg 100 g<sup>−</sup>1) (*p* < 0.05), regardless of specimens' sex. However, Cu, Zn, Mn, and Se completely inverted such trend, showing to be more abundant in oral arms than bells (*p* < 0.05). Also, Zn and Mn contents showed a slight dependence on the specimens' sex, though in a nonstatistically significant manner (*p* > 0.05), since males showed to most bioaccumulate such elements than females in both bell and oral arms. Being not ye<sup>t</sup> determined in any jellyfish species, Se levels ranged from 31.2 to 46.2 μg 100 g<sup>−</sup><sup>1</sup> in bells and from 100 to 115 μg 100 g<sup>−</sup><sup>1</sup> in oral arms (Table 2).

Nonessential/toxic trace elements were reported in the decreasing order of Cr ≈As > Ni > Pb > Cd. Such elements were slightly higher in oral arms than in bells (*p* > 0.05 in almost all cases), and, with the exception of Pb, marginally more bioaccumulated in male organisms than female ones (*p* > 0.05) as well. Cr and As varied respectively between 401 and 573 μg 100 g<sup>−</sup><sup>1</sup> and 412 and 528 μg 100 g<sup>−</sup><sup>1</sup> in female and male bells; while female and male oral arms reported Cr and As levels of 668 to 631 <sup>μ</sup>g·100 g<sup>−</sup><sup>1</sup> and 690 to 663 <sup>μ</sup>g·100 g<sup>−</sup>1, respectively. Contrary to Cr and As, Pb exhibited the lowest contents in both bells (140–117 μg 100 g<sup>−</sup>1) and oral arms (154–132 μg 100 g<sup>−</sup>1), with comparable values between female and male specimens (Table 2).
