Fatty acid profiles during gametogenesis in sea urchin (Paracentrotus lividus): effects of dietary inputs on gonad, egg and embryo profiles

Metal accumulation in female green sea turtles (Chelonia mydas) from Eastern Atlantic affects their egg quality with potential implications for embryonic development

Sea turtles, with their global distribution and complex life cycle, often accumulate pollutants such as metals and metalloids due to their extended lifespan and feeding habits. However, there are limited studies exploring the impact of metal pollution on the reproductive health of female sea turtles, specifically focusing on the quality of their eggs, which has significant implications for the future generations of these charismatic animals. São Tomé Island, a crucial nesting and feeding habitat for green sea turtles, underscores the urgent need for comprehensive research in this ecologically significant area. This study aimed to investigate whether metals and metalloids in the blood of nesting female green sea turtles induce genotoxic effects in their erythrocytes and affect their egg morphometric characteristics and the composition of related compartments. Additionally, this study aimed to evaluate whether the quality of energetic reserves for embryo development (fatty acids in yolk's polar and neutral lipids) is influenced by the contamination status of their predecessors. Results revealed correlations between Cu and Hg levels and increased "lobed" erythrocytes, while As and Cu negatively influenced shell thickness. In terms of energy reserves, both polar and neutral lipid fractions contained primarily saturated and monounsaturated fatty acids, with prevalent 18:1n-9, 18:0, 16:0, 14:0, and 12:0 fatty acids in yolk samples. The yolk polar fraction was more susceptible to contaminant levels in female sea turtles, showing consistent negative correlations between pollution load index and essential n3 fatty acids, including linolenic, eicosatrienoic, eicosapentaenoic, and docosapentaenoic acids, crucial for embryonic development. These metals accumulation, coupled with the reduced availability of these key fatty acids, may disrupt the eicosanoid and other important pathways, affecting reproductive development. This study reveals a negative correlation between metal contamination in female sea turtles' blood and egg lipid reserves, raising concerns about embryonic development and the species' future generations.

Fatty Acids of Echinoderms: Diversity, Current Applications and Future Opportunities

The phylum Echinodermata comprising the classes Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea, and Crinodeia, is one of the important invertebrate groups. Members of this phylum live exclusively in marine habitats and are distributed in almost all depths and latitudes. Some of them, such as sea urchins and sea cucumbers, are commercially valuable and constitute a major fishery resource. Echinoderms are increasingly recognized as a unique source of various metabolites with a wide range of biological activities. The importance of dietary polyunsaturated fatty acids, such as eicosapentaenoic acid, in human health has drawn attention to echinoderms as a promising source of essential fatty acids (FAs). Extensive information on the FAs of the phylum has been accumulated to date. The biosynthetic capabilities and feeding habits of echinoderms explain the findings of the unusual FAs in them. Certain common and unusual FAs may serve as chemotaxonomic markers of the classes. The main goal of the review was to gather the relevant information on the distribution of FAs among the echinoderm classes, describe the structures, distribution, biosynthetic pathways, and bioactivity, with an emphasis on the FAs specific for echinoderms. A large part of the review is devoted to the FAs derived from echinoderms that exhibit various biological activities promising for potential therapeutic applications.

Detection of microplastics and phthalic acid esters in sea urchins from Sardinia (Western Mediterranean Sea)

The occurrence of microplastics (MPs) and phthalic acid esters (PAEs) in wild purple sea urchins (Paracentrotus lividus) of Sardinia (Italy, Western Mediterranean Sea) was surveyed. Specifically, MPs were analyzed in the digestive tract by μFTIR and PAEs in the gonads by SPME-LC-MS/MS. 9 out of 22 specimens resulted contaminated with MPs and 20 displayed levels of PAEs over the quantification limit. A total of 23 MPs were detected with a maximum concentration of 4 microplastics/individual in the commercially undersized specimens. PAEs displayed average concentration of 32 ng/g, σ = 5.3 with maximum value of 77 ng/g. The most abundant congeners were DEHP (17 ng/g, σ = 4.3) and DBP (10 ng/g, σ = 2.5). Statistical analysis showed correlation between DEHP and fiber concentrations and among the concentration of MEP, DEP, DBP and BBzP. Due to local use of sea urchin gonads as gourmet delicacy, the potential human exposition to MPs and PAEs by consumption is also discussed.

Stable isotope and fatty acid analysis reveal the ability of sea cucumbers to use fish farm waste in integrated multi-trophic aquaculture

Stable isotope ratios, carbon (δ¹³C) and nitrogen (δ¹⁵N), and fatty acids validated the trophic connection between farmed fish in a commercial nearshore fish farm and sea cucumbers in the Mediterranean Sea. This dual tracer approach evaluated organic matter transfer in integrated multi-trophic aquaculture (IMTA) and the ability of sea cucumbers to incorporate fish farm waste (fish faeces and uneaten artificial fish feed) into their tissue. Between October 2018 and September 2019, Holothuria (Roweothuria) poli Delle Chiaje, 1824, co-cultured at IMTA sites directly below one of the commercial fish cage , at 10 m and 25 m from the selected fish cage, and at two reference sites over 800 m from the fish farm. Sea cucumbers were sampled from each site in February, May and September, except at 0 m due to mass mortalities recorded here in the first month of study. Isotopic mixing models revealed that fish farm organic waste was the dominant dietary source for H. poli in IMTA at 10 m and 25 m from the cage. The contribution of marine plant-derived organic matter, Posidonia oceanica leaves and rhizomes, was least important. The isotopic signatures of sea cucumber tissues at reference sites were not explained by the sampled food resources. Importantly, fatty acid profiling revealed a high abundance of individual terrestrial plant fatty acids, such as oleic (18:1n-9), linoleic (18:2n-6) and eicosenoic (20:1n-9) acids in sea cucumber tissue at 10 m and 25 m from the fish cage, presumably linked to the terrestrial plant oil content of the fish feeds. At the reference sites, sea cucumber tissues were characterised by higher relative abundance of arachidonic acid (20:4n-6) acid, and the natural marine-based eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acids. These analyses revealed important differences in the composition of H. poli between the IMTA and reference locations, driven by aquaculture-derived waste near fish cages. Moreover, this study revealed temporal variation in food availability and quality, and possible differences in the physiological responses of H. poli. Stable isotope analysis and fatty acid profiling provided complementary evidence for the important dietary preferences of H. poli and validated the potential of sea cucumbers to uptake aquaculture organic waste as part of inshore fish-sea cucumber IMTA. It reveals the important implications that an established trophic link has on the viability of using sea cucumbers for the development of IMTA and the sustainable expansion of aquaculture.

Photosynthesis from stolen chloroplasts can support sea slug reproductive fitness

Some sea slugs are able to steal functional chloroplasts (kleptoplasts) from their algal food sources, but the role and relevance of photosynthesis to the animal host remain controversial. While some researchers claim that kleptoplasts are slowly digestible 'snacks', others advocate that they enhance the overall fitness of sea slugs much more profoundly. Our analysis shows light-dependent incorporation of 13C and 15N in the albumen gland and gonadal follicles of the sea slug Elysia timida, representing translocation of photosynthates to kleptoplast-free reproductive organs. Long-chain polyunsaturated fatty acids with reported roles in reproduction were produced in the sea slug cells using labelled precursors translocated from the kleptoplasts. Finally, we report reduced fecundity of E. timida by limiting kleptoplast photosynthesis. The present study indicates that photosynthesis enhances the reproductive fitness of kleptoplast-bearing sea slugs, confirming the biological relevance of this remarkable association between a metazoan and an algal-derived organelle.

Lipid metabolism of sea urchin Paracentrotus lividus in two contrasting natural habitats

Sea urchins Paracentrotus lividus were harvested monthly from April 2015 to March 2016 from two sites in Sardinia (Italy). The two sites, a Posidonia oceanica meadow and a rocky bottom habitat, were naturally characterized by different food sources and availability, being mainly populated by the sea grass Posidonia oceanica and the brown algae Halopteris scoparia, respectively. Total lipids showed a minimum during winter in mature gonads, and a maximum in the summer (recovery stage). Fatty acid (FA) profiles of gut contents and gonads differed from those of the most available food sources. Levels of C18:3 (n-3) (ALA) discriminated samples from the two sites. Despite the very low amounts of C20:5 (n-3) (EPA) and C20:4 (n-6) (ARA) in P. oceanica, the main FA in gonads and gut contents were EPA and ARA in both sites. Increase in green algae intake prior to gametogenesis, especially C. cylindracea, likely affected EPA and ARA levels in gonads. The results show that P. lividus is able to concentrate lipids in gut contents and also to selectively store EPA, ARA and their precursors ALA and 18:2 (n-6) (LA). Moreover, bioconversion of ALA to EPA and of LA to ARA in P. lividus is suggested.

The Echinodermata PPAR: Functional characterization and exploitation by the model lipid homeostasis regulator tributyltin

The wide ecological relevance of lipid homeostasis modulators in the environment has been increasingly acknowledged. Tributyltin (TBT), for instance, was shown to cause lipid modulation, not only in mammals, but also in fish, molluscs, arthropods and rotifers. In vertebrates, TBT is known to interact with a nuclear receptor heterodimer module, formed by the retinoid X receptor (RXR) and the peroxisome proliferator-activated receptor (PPAR). These modulate the expression of genes involved in lipid homeostasis. In the present work, we isolated for the first time the complete coding region of the Echinodermata (Paracentrotus lividus) gene orthologues of PPAR and RXR and evaluated the ability of a model lipid homeostasis modulator, TBT, to interfere with the lipid metabolism in this species. Our results demonstrate that TBT alters the gonadal fatty acid composition and gene expression patterns: yielding sex-specific responses in fatty acid levels, including the decrease of eicosapentaenoic acid (C20:5 n-3, EPA) in males, and increase of arachidonic acid (20:4n-6, ARA) in females, and upregulation of long-chain acyl-CoA synthetase (acsl), ppar and rxr. Furthermore, an in vitro test using COS-1 cells as host and chimeric receptors with the ligand binding domain (LBD) of P. lividus PPAR and RXR shows that organotins (TBT and TPT (Triphenyltin)) suppressed activity of the heterodimer PPAR/RXR in a concentration-dependent manner. Together, these results suggest that TBT acts as a lipid homeostasis modulator at environmentally relevant concentrations in Echinodermata and highlight a possible conserved mode of action via the PPAR/RXR heterodimer.

Molecular characterization and expression of SiFad1 in the sea urchin (Strongylocentrotus intermedius)

Fatty acid desaturases (Fads) are a key enzyme in the process of biosynthesis of highly unsaturated fatty acids (HUFAs). In this study, we cloned the full-length sequence of the SiFad1 gene (SiFad1) and analyzed its expression profiles during different developmental stages and in different tissues of Strongylocentrotus intermedius. The full-length cDNA of SiFad1 is composed of 1086 bp, with a putative open reading frame of 885 bp encoding a polypeptide of 294 amino acid (AA) residues. The predicted molecular mass of SiFad1 is 34.67 kDa and its theoretical pI is 8.41. The presence of conserved motifs including three histidine boxes (HXXXH, HXXHH, XXXHH), a FA_desaturases domain and three transmembrane domains suggests that SiFad1 belongs to the microsomal fatty acid desaturases family. Its tissue distribution showed that the highest expression of SiFad1 is in the intestine and the weakest expression is in Aristotle's lantern of S. intermedius. Time-course expression measurements in different developmental stages showed the highest expression of SiFad1 occurs in the gastrula and the weakest expression in the juvenile sea urchin. Knock-down of SiFad1 by specific siRNA revealed that the significantly depressed expression of Elovl5 had decreased in the coelomocytes, intestines and gonads at 24 h post transfection, indicating that the downstream target gene of SiFad1 is Elovl5 and SiFad1 and Elovl5 have positive regulatory effects. When we examined the changes in fatty acids in the gonads before and after interference, the results showed that after 24 h of interference, the content of C20:4n-6 produced by SiFad1 had decreased. Taken together, these results will enable us to understand the role of SiFad1 in fatty acid anabolism, which will help us to understand the fatty acid synthesis pathways and regulatory mechanisms of Strongylocentrotus intermedius and provide a theoretical experimental basis for improving the ability of sea urchins to synthesize fatty acids and cultivating sea urchins of higher quality and nutritional value.

De novo transcriptomic analysis of gonad of Strongylocentrotus nudus and gene discovery for biosynthesis of polyunsaturated fatty acids

BACKGROUND

Strongylocentrotus nudus is an important cultured sea urchin species in north China, because its gonad is rich in unsaturated fatty acids, particularly long polyunsaturated fatty acids (LC-PUFAs). These PUFAs play pleiotropic and crucial roles in a wide range of biological process.

OBJECTIVE

However, the genes contributing to biosynthesis PUFAs have not been elucidated yet, and the molecular mechanism relative to the difference in PUFA composition between male and female gonad as been revealed but the corresponding has not been understood.

METHODS

In this paper, solexa sequencing based transcriptomic approach was used to identify and characterize the key genes relative to PUFA synthesis and further conducted different expressed genes between male and female gonad.

RESULTS

A total of 130,124 transcripts and 189330 unigenes were de novo assembled from 64.32 Gb data. Next, these unigenes were subjected to functional annotation by mapping to six public databases, and this process revealed a lot of genes involving in lipid metabolism. In addition, three types of fatty acids front-end desaturase and three species of very long fatty acids elongase were identified and the pathway for PUFA biosynthesis was hypothesized. Last, comparative analysis revealed the higher expression level of Δ5 desaturase, Δ6 desaturase, ELOVL-4, -6 and -7 in male gonad compared with female.

CONCLUSION

This results could plausible explain the differ in composition of PUFAs between male and female gonad of sea urchin.

The effect of sex, season and gametogenic cycle on gonad yield, biochemical composition and quality traits of Paracentrotus lividus along the North Atlantic coast of Portugal

Sea urchin population harvest in the North Atlantic coast of Portugal was characterized in terms of gonad yield, nutritional composition and important market-related traits, over one reproductive cycle (March 2016 to March 2017). Most of the quality attributes showed a seasonal variation strongly dependent on sea urchin sex. Maximum gonad yield (18%) was observed in March 2017. A single spawning event occurred between May and July. Gonads are rich sources of protein (12–18% WW) with low fat content (≤6% WW), that increase during the gametogenic stages of recovery and growing (November-December). Polyunsaturated fatty acids were the dominant class in both sexes (4.2–14.7 mg.g⁻¹ WW), being preferentially accumulated in females. Total gonads carotenoid varied seasonally, with the highest level being observed in males during spawning season. Echinenone was the main pigment present in gonads, showing highest concentrations in males during spawning and gonad recovering. During the growing and early maturation period gonads were more reddish, yellowish and brighter, as well as more firm, irrespectively of the sex. Based on all seasonal changes affecting gonad yield and quality, the period between November and February seems the most suitable to harvest high quality gonads in the Atlantic coast of Portugal.

Differences in Small Molecule Neurotransmitter Profiles From the Crown-of-Thorns Seastar Radial Nerve Revealed Between Sexes and Following Food-Deprivation

Neurotransmitters serve as chemical mediators of cell communication, and are known to have important roles in regulating numerous physiological and metabolic events in eumetazoans. The Crown-of-Thorns Seastar (COTS) is an asteroid echinoderm that has been the focus of numerous ecological studies due to its negative impact on coral reefs when in large numbers. Research devoted to its neural signaling, from basic anatomy to the key small neurotransmitters, would expand our current understanding of neural-driven biological processes, such as growth and reproduction, and offers a new approach to exploring the propensity for COTS population explosions and subsequent collapse. In this study we investigated the metabolomic profiles of small molecule neurotransmitters in the COTS radial nerve cord. Multivariate analysis shows differential abundance of small molecule neurotransmitters in male and female COTS, and in food-deprived individuals with significant differences between sexes in gamma-aminobutyric acid (GABA), histamine and serotonin, and significant differences in histamine and serotonin between satiation states. Annotation established that the majority of biosynthesis enzyme genes are present in the COTS genome. The spatial distribution of GABA, histamine and serotonin in the radial nerve cord was subsequently confirmed by immunolocalization; serotonin is most prominent within the ectoneural regions, including unique neural bulbs, while GABA and histamine localize primarily within neuropil fibers. Glutamic acid, which was also found in high relative abundance and is a precursor of GABA, is known as a spawning inhibitor in seastars, and as such was tested for inhibition of ovulation ex-vivo which resulted in complete inhibition of oocyte maturation and ovulation induced by 1-Methyladenine. These findings not only advance our knowledge of echinoderm neural signaling processes but also identify potential targets for developing novel approaches for COTS biocontrol.

The role of fatty acids and triglycerides in the gonads of Paracentrotus lividus from Sardinia: Growth, reproduction and cold acclimatization

A detailed characterization of lipid extracts from gonads of P. lividus over a year has been performed combining GC and NMR measurements. For this purpose, sea urchins from two different Sardinian coastal areas were collected monthly. The results underlined a correlation between gonad fatty acids profiles and both water temperature and reproduction process. In particular, EPA and ARA appear to be the most altered fatty acids following seasonal changes. It is suggested that EPA could represent a biomarker of reproduction, reaching a content around 14% during gametogenesis, mainly due to an increase of the sn-1,3 position in TAGs. On the contrary, ARA seems to play a more important role in response to cold acclimatization, which is reflected in a modulation of ARA content in the sn-1,3 position in TAGs.

Biosynthesis of Polyunsaturated Fatty Acids in Sea Urchins: Molecular and Functional Characterisation of Three Fatty Acyl Desaturases from Paracentrotus lividus (Lamark 1816)

Sea urchins are broadly recognised as a delicacy and their quality as food for humans is highly influenced by their diet. Lipids in general and the long-chain polyunsaturated fatty acids (LC-PUFA) in particular, are essential nutrients that determine not only the nutritional value of sea urchins but also guarantee normal growth and reproduction in captivity. The contribution of endogenous production (biosynthesis) of LC-PUFA in sea urchins remained unknown. Using Paracentrotus lividus as our model species, we aimed to characterise both molecularly and functionally the repertoire of fatty acyl desaturases (Fads), key enzymes in the biosynthesis of LC-PUFA, in sea urchins. Three Fads, namely FadsA, FadsC1 and FadsC2, were characterised. The phylogenetic analyses suggested that the repertoire of Fads within the Echinodermata phylum varies among classes. On one hand, orthologues of the P. lividus FadsA were found in other echinoderm classes including starfishes, brittle stars and sea cucumbers, thus suggesting that this desaturase is virtually present in all echinoderms. Contrarily, the FadsC appears to be sea urchin-specific desaturase. Finally, a further desaturase termed as FadsB exists in starfishes, brittle stars and sea cucumbers, but appears to be missing in sea urchins. The functional characterisation of the P. lividus Fads confirmed that the FadsA was a Δ5 desaturase with activity towards saturated and polyunsaturated fatty acids (FA). Moreover, our experiments confirmed that FadsA plays a role in the biosynthesis of non-methylene interrupted FA, a group of compounds typically found in marine invertebrates. On the other hand, both FadsC desaturases from P. lividus showed Δ8 activity. The present results demonstrate that P. lividus possesses desaturases that account for all the desaturation reactions required to biosynthesis the physiological essential eicosapentaenoic and arachidonic acids through the so-called "Δ8 pathway".

A Rapid Colorimetric Method Reveals Fraudulent Substitutions in Sea Urchin Roe Marketed in Sardinia (Italy)

In recent years, besides the consumption of fresh sea urchin specimens, the demand of minimally-processed roe has grown considerably. This product has made frequent consumption in restaurants possible and frauds are becoming widespread with the partial replacement of sea urchin roe with surrogates that are similar in colour. One of the main factors that determines the quality of the roe is its colour and small differences in colour scale cannot be easily discerned by the consumers. In this study we have applied a rapid colorimetric method for reveal the fraudulent partial substitution of semi-solid sea urchin roe with liquid egg yolk. Objective assessment of whiteness (L*), redness (a*), yellowness (b*), hue (h*), and chroma (C*) was carried out with a digital spectrophotometer using the CIE L*a*b* colour measurement system. The colorimetric method highlighted statistically significant differences among sea urchin roe and liquid egg yolk that could be easily discerned quantitatively.

Influence of seasonal and environmental patterns on the lipid content and fatty acid profiles in gonads of the edible sea urchin Paracentrotus lividus from Sardinia

The influence of seasonal and environmental patterns on the lipid fraction of Paracentrotus lividus gonads was investigated. For this purpose, sea urchins were collected monthly over a year from two Sardinian coastal areas. Total lipids in gonads follow an annual cyclical trend, described by a sine wave curve, that it is more influenced by season than by growing area. The lowest lipid content in gonads corresponds to a high percentage of mature reproductive stages (i.e. winter season), independently of sampling area. A variation in total lipid content follows a change in photoperiod, while it is related to sea surface temperature. Multivariate analysis on fatty acid profiles of gonads, detected by gas chromatography, clusters the collected specimens mainly according to the sampling area, secondly according to the sites within the same sampling area and finally according to season.

Mediterranean fouling communities assimilate the organic matter derived from coastal fish farms as a new trophic resource

Currently, the lipid content of fish feeds includes high amounts of terrestrial vegetable oils, rich in n-6 fatty acids and poor in n-3 fatty acids. Sinking organic matter in the shape of fragmented pellets and fish faeces could be ingested by the surrounding fauna attracted to the submerged structures of aquaculture facilities or living in natural benthic habitats. Fatty acids contained in feed pellets were used as trophic markers to shed light on the assimilation and incorporation of aquaculture wastes by the invertebrate fauna associated to sea-cages. Eighteen macroinvertebrate species, and zooplankton, seaweeds and sediments were collected from two fish farms, one of which (control) had not been used as such for two years. This study demonstrates that macroinvertebrate fauna present in fouling can take up sinking organic matter from farms. Further research should be directed at assessing the potential implications of aquaculture production for the surrounding ecosystem.