Two Benthic Diatoms, Nanofrustulum shiloi and Striatella unipunctata, Encapsulated in Alginate Beads, Influence the Reproductive Efficiency of Paracentrotus lividus by Modulating the Gene Expression.

Physiological effects of algal metabolites is a key step for the isolation of interesting bioactive compounds. Invertebrate grazers may be fed on live diatoms or dried, pelletized, and added to compound feeds. Any method may reveal some shortcomings, due to the leaking of wound-activated compounds in the water prior to ingestion. For this reason, encapsulation may represent an important step of bioassay-guided fractionation, because it may assure timely preservation of the active compounds. Here we test the effects of the inclusion in alginate (biocompatible and non-toxic delivery system) matrices to produce beads containing two benthic diatoms for sea urchin Paracentrotus lividus feeding. In particular, we compared the effects of a diatom whose influence on P. lividus was known (Nanofrustulum shiloi) and those of a diatom suspected to be harmful to marine invertebrates, because it is often present in blooms (Striatella unipunctata). Dried N. shiloi and S. unipunctata were offered for one month after encapsulation in alginate hydrogel beads and the larvae produced by sea urchins were checked for viability and malformations. The results indicated that N. shiloi, already known for its toxigenic effects on sea urchin larvae, fully conserved its activity after inclusion in alginate beads. On the whole, benthic diatoms affected the embryogenesis of P. lividus, altering the expression of several genes involved in stress response, development, skeletogenesis and detoxification processes. Interactomic analysis suggested that both diatoms activated a similar stress response pathway, through the up-regulation of hsp60, hsp70, NF-κB, 14-3-3 ε and MDR1 genes. This research also demonstrates that the inclusion in alginate beads may represent a feasible technique to isolate diatom-derived bioactive compounds.

Composition and geographic variation of the bacterial microbiota associated with the coelomic fluid of the sea urchin Paracentrotus lividus.

In the present work, culture-based and culture-independent investigations were performed to determine the microbiota structure of the coelomic fluid of Mediterranean sea urchin Paracentrotus lividus individuals collected from two distinct geographical sites neighboring a high-density population bay and a nature reserve, respectively. Next Generation Sequencing analysis of 16S rRNA gene (rDNA) showed that members of the Proteobacteria, Bacteroidetes and Fusobacteria phyla, which have been previously reported to be commonly retrieved from marine invertebrates, dominate the overall population of microorganisms colonizing this liquid tissue, with minority bacterial genera exhibiting remarkable differences among individuals. Our results showed that there is a correlation between microbiota structure and geographical location of the echinoderm collection site, highlighting over-representation of metagenomic functions related to amino acid and bioactive peptides metabolism in specimens inhabiting the nature reserve. Finally, we also described the developmental delay and aberrations exhibited by sea urchin embryos exposed to distinct bacterial isolates, and showed that these defects rely upon hydrophilic compound(s) synthesized by the bacterial strains assayed. Altogether, our findings lay the groundwork to decipher the relationships of bacteria with sea urchins in their aquatic environment, also providing an additional layer of information to understand the biological roles of the coelomic fluid.

Responses to iron oxide and zinc oxide nanoparticles in echinoderm embryos and microalgae: uptake, growth, morphology, and transcriptomic analysis.

We investigated the toxicity of Iron oxide and Zinc oxide engineered nanoparticles (ENPs) on Paracentrotus lividus sea urchin embryos and three species of microalgae. Morphological responses, internalization, and potential impacts of Fe2O3 and ZnO ENPs on physiology and metabolism were assessed. Both types of ENPs affected P. lividus larval development, but ZnO ENPs had a much stronger effect. While growth of the alga Micromonas commoda was severely impaired by both ENPs, Ostreococcus tauri or Nannochloris sp. were unaffected. Transmission electron microscopy showed the internalization of ENPs in sea urchin embryonic cells while only nanoparticle interaction with external membranes was evidenced in microalgae, suggesting that marine organisms react in diverse ways to ENPs. Transcriptome-wide analysis in P. lividus and M. commoda showed that many different physiological pathways were affected, some of which were common to both species, giving insights about the mechanisms underpinning toxic responses.

Polyethylene microplastics do not increase bioaccumulation or toxicity of nonylphenol and 4-MBC to marine zooplankton.

Global production of synthetic polymers, led by polyethylene (PE), rose steadily in the last decades, and marine ecosystems are considered as a global sink. Although PE is not biodegradable, in coastal areas it fragments into microplastics (MP) readily taken up by biota, and have been postulated as vectors of hydrophobic chemicals to marine organisms. We have tested this hypothesis using two organisms representative of the marine plankton, the holoplanktonic copepod Acartia clausi, and the meroplanktonic larva of the Paracentrotus lividus sea-urchin, and two model chemicals with similar hydrophobic properties, the 4-n-Nonylphenol and the 4-Methylbenzylidene-camphor used as plastic additive and UV filter in cosmetics. Both test species actively ingested the MP particles. However, the presence of MP never increased the bioaccumulation of neither model chemicals, nor their toxicity to the exposed organisms. Bioaccumulation was a linear function of waterborne chemical disregarding the level of MP. Toxicity, assessed by the threshold (EC10) and median (EC50) effect levels, was either independent of the level of MP or even in some instances significantly decreased in the presence of MPs. These consistent results challenge the assumption that MP act as vectors of hydrophobic chemicals to planktonic marine organisms.

Assessment of individual and mixed toxicity of bromoform, tribromoacetic-acid and 2,4,6 tribromophenol, on the embryo-larval development of Paracentrotus lividus sea urchin.

Water chlorination is the most widely used technique to avoid microbial contamination and biofouling. Adding chlorine to bromide-rich waters leads to the rapid oxidation of bromide ions and leads to the formation of brominated disinfection by-products (bromo-DBPs) that exert adverse effects on various biological models. Bromo-DBPs are regularly encountered within industrialized embayments, potentially impacting marine organisms. Of these, bromoform, tribromoacetic acid and tribromophenol are among the most prevalent. In the present study, we tested the potential toxicity and genotoxicity of these disinfection by-products, using sea urchin, Paracentrotus lividus, embryos. We highlighted that tribromophenol showed higher toxicity compared to bromoform and tribromoacetic acid. Furthermore, a synergistic effect was detected when tested in combination. Pluteus cells exposed for 1 h to mixtures of DBPs at several concentrations demonstrated significant DNA damage. Finally, when compared to a non-exposed population, sea urchins living in a bromo-DPB-polluted area produced more resistant progenies, as if they were locally adapted. This hypothesis remains to be tested in order to better understand the obvious impact of complex bromo-DBPs environments on marine wildlife.

Molecular and Morphological Toxicity of Diatom-Derived Hydroxyacid Mixtures to Sea Urchin Paracentrotus lividus Embryos.

Oxylipins such as polyunsaturated aldehydes (PUAs) and hydroxyacids (HEPEs) are signaling molecules derived from the oxidation of polyunsaturated fatty acids. They are common in diatoms that constitute a major group of microalgae in freshwater and oceanic ecosystems. Although HEPEs represent the most common oxylipins produced by diatoms, little information is available on their effects on marine invertebrates, and most of the information has been obtained by testing individual HEPEs. Our previous studies reported that four hydroxyacids, i.e., 5-, 9-, 11-, and 15-HEPE, were able to induce malformations and a marked developmental delay in sea urchin Paracentrotus lividus embryos, which had not been reported for other oxylipins. Here, we tested a mixture of 5-, 9-, 11-, and 15-HEPE at different concentrations for the first time. The results showed that mixtures of HEPEs have synergistic effects that are much more severe compared to those of individual HEPEs: The HEPE mixtures induced malformations in sea urchin embryos at lower concentrations. Increasing HEPE mixture concentrations induced a marked increase in the number of delayed embryos, until all embryos were delayed at the highest concentration tested. At the molecular level, the HEPE mixtures induced variations in the expression of 50 genes involved in different functional processes, mainly down-regulating these genes at the earliest stages of embryonic development. These findings are ecologically significant, considering that during diatom blooms, sea urchins could accumulate HEPEs in concentrations comparable to those tested in the present study.

Mifepristone affects fertility and development in the sea urchin Paracentrotus lividus.

Drugs such as oral contraceptives and hormone replacement therapies are known to find their way into rivers, lakes and seas, and have the potential to affect reproduction and development of the wildlife. The knowledge of the reproductive mechanisms and their regulation in aquatic species is of fundamental importance for predicting and preventing the damage by the increasing release of such chemicals in the environment. Mifepristone, a synthetic steroid used as a drug for chemical abortion, works by blocking the effects of progesterone. Its presence in fresh and salt water has been reported, representing a danger for aquatic species. In this frame, we evaluated in both acute and chronic exposures, the effects of mifepristone on the reproductive performance of the sea urchin P. lividus. In both acute and chronic exposures, mifepristone did not affect the histological structure of the gonads. However, mifepristone administered to females caused the decrease of the percentage of normal developed plutei larvae compared with the control, whereas it did not alter sperm motility parameters and fertilization success in males. The immunohistological localization of progesterone receptor-like immunoreactivity on the plasma membrane of oocytes and ova and the molecular weight of a progesterone receptor-like immunoband identified by western blotting, are in agreement with a membrane progesterone receptor deducted from the genome sequence of the sea urchin Strongylocentrotus purpuratus and suggest that in P. lividus mifepristone actions may be mediated by a progesterone receptor.

A 2-Tier standard method to test the toxicity of microplastics in marine water using Paracentrotus lividus and Acartia clausi larvae.

A 2-tier standardized protocol was designed to test the toxicity of microplastics to planktonic organisms. This approach uses sea urchin (Paracentrotus lividus) and copepod (Acartia clausi) larvae because they are common biological models in marine research, and standard methods for toxicity testing with regulatory applications are available. In Tier I, leachates obtained at a 100 to 1 liquid to solid ratio are tested, and toxic units are calculated using a probit dose-response model to quantify the toxicity of the plastics. In Tier II, which is conducted only if significant toxicity (> 1 toxic unit) is found in Tier I, particles less than 20 µm in size are tested at concentrations between 0.1 and 10 mg L-1 , and a toxicity threshold suitable for ranking materials according to their toxicity is obtained from the 10% effect concentration (EC10) values. Results point to chemical additives as being responsible for the toxicity found in certain plastic materials. This process is suitable for both a priori identification of the hazard posed by plastic objects in the aquatic environment, and a posteriori assessment of environmental risk caused by microplastic pollution. The method also provides a quantitative procedure appropriate for ranking plastic materials according to their toxicity to aquatic organisms. Environ Toxicol Chem 2019;38:630-637. © 2018 SETAC.

MAPK and GSK3/ß-TRCP-mediated degradation of the maternal Ets domain transcriptional repressor Yan/Tel controls the spatial expression of nodal in the sea urchin embryo.

In the sea urchin embryo, specification of the dorsal-ventral axis critically relies on the spatially restricted expression of nodal in the presumptive ventral ectoderm. The ventral restriction of nodal expression requires the activity of the maternal TGF-ß ligand Panda but the mechanism by which Panda restricts nodal expression is unknown. Similarly, what initiates expression of nodal in the ectoderm and what are the mechanisms that link patterning along the primary and secondary axes is not well understood. We report that in Paracentrotus lividus, the activity of the maternally expressed ETS-domain transcription factor Yan/Tel is essential for the spatial restriction of nodal. Inhibiting translation of maternal yan/tel mRNA disrupted dorsal-ventral patterning in all germ layers by causing a massive ectopic expression of nodal starting from cleavage stages, mimicking the phenotype caused by inactivation of the maternal Nodal antagonist Panda. We show that like in the fly or in vertebrates, the activity of sea urchin Yan/Tel is regulated by phosphorylation by MAP kinases. However, unlike in the fly or in vertebrates, phosphorylation by GSK3 plays a central role in the regulation Yan/Tel stability in the sea urchin. We show that GSK3 phosphorylates Yan/Tel in vitro at two different sites including a ß-TRCP ubiquitin ligase degradation motif and a C-terminal Ser/Thr rich cluster and that phosphorylation of Yan/Tel by GSK3 triggers its degradation by a ß-TRCP/proteasome pathway. Finally, we show that, Yan is epistatic to Panda and that the activity of Yan/Tel is required downstream of Panda to restrict nodal expression. Our results identify Yan/Tel as a central regulator of the spatial expression of nodal in Paracentrotus lividus and uncover a key interaction between the gene regulatory networks responsible for patterning the embryo along the dorsal-ventral and animal-vegetal axes.

Biotic and environmental stress induces nitration and changes in structure and function of the sea urchin major yolk protein toposome.

The major yolk protein toposome plays crucial roles during gametogenesis and development of sea urchins. We previously found that nitration of toposome increases in the gonads of a Paracentrotus lividus population living in a marine protected area affected by toxic blooms of Ostreospsis cf. ovata, compared to control populations. This modification is associated with ovatoxin accumulation, high levels of nitric oxide in the gonads, and a remarkable impairment of progeny development. However, nothing is known about the environmental-mediated-regulation of the structure and biological function of toposome. Here, we characterize through wide-ranging biochemical and structural analyses the nitrated toposome of sea urchins exposed to the bloom, and subsequently detoxified. The increased number of nitrated tyrosines in toposome of sea urchins collected during algal bloom induced structural changes and improvement of the Ca2+-binding affinity of the protein. After 3 months' detoxification, ovatoxin was undetectable, and the number of nitric oxide-modified tyrosines was reduced. However, the nitration of specific residues was irreversible and occurred also in embryos treated with metals, used as a proxy of environmental pollutants. The structural and functional changes of toposome caused by nitration under adverse environmental conditions may be related to the defective development of sea urchins' progeny.

Gadolinium perturbs expression of skeletogenic genes, calcium uptake and larval development in phylogenetically distant sea urchin species.

Chelates of Gadolinium (Gd), a lanthanide metal, are employed as contrast agents for magnetic resonance imaging and are released into the aquatic environment where they are an emerging contaminant. We studied the effects of environmentally relevant Gd concentrations on the development of two phylogenetically and geographically distant sea urchin species: the Mediterranean Paracentrotus lividus and the Australian Heliocidaris tuberculata. We found a general delay of embryo development at 24h post-fertilization, and a strong inhibition of skeleton growth at 48h. Total Gd and Ca content in the larvae showed a time- and concentration-dependent increase in Gd, in parallel with a reduction in Ca. To investigate the impact of Gd on the expression of genes involved in the regulation of skeletogenesis, we performed comparative RT-PCR analysis and found a misregulation of several genes involved in the skeletogenic and left-right axis specification gene regulatory networks. Species-specific differences in the biomineralization response were evident, likely due to differences in the skeletal framework of the larvae and the amount of biomineral produced. Our results highlight the hazard of Gd for marine organisms.

Sunscreen products impair the early developmental stages of the sea urchin Paracentrotus lividus.

Marine ecosystems are increasingly threatened by the release of personal care products. Among them, sunscreens are causing concern either for the effects on skin protection from UV radiation and for the potential impacts on marine life. Here, we assessed the UVA protective efficacy of three sunscreens on human dermal fibroblasts, including two common products in Europe and USA, and an eco-friendly product. The sunscreens' effects were also tested on Paracentrotus lividus, a marine species possibly threatened by these contaminants. We found that all tested sunscreens had similar efficacy in protecting human fibroblasts from UVA radiation. Conversely, the sunscreens' effects on embryo-larval development of P. lividus were dependent on the product tested. In particular, the USA sunscreen, containing benzophenone-3, homosalate and preservatives, caused the strongest impact on the sea urchin development, whereas the eco-friendly sunscreen determined the weakest effects. These results suggest that although the tested products protected human skin cells from UVA-induced damage, they might severely affect the success of recruitment and survival of the sea urchin. Our findings underline the importance of developing eco-friendly sunscreens for minimising or avoiding the impact on marine life while protecting human skin from UV damage.

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.

High-quality RNA extraction from the sea urchin Paracentrotus lividus embryos.

The sea urchin Paracentrotus lividus (Lamarck, 1816) is a keystone herbivore in the Mediterranean Sea due to its ability to transform macroalgal-dominated communities into barren areas characterized by increased cover of bare substrates and encrusting coralline algae, reduced biodiversity and altered ecosystem functions. P. lividus is also an excellent animal model for toxicology, physiology and biology investigations having been used for more than a century as a model for embryological studies with synchronously developing embryos which are easy to manipulate and analyze for morphological aberrations. Despite its importance for the scientific community, the complete genome is still not fully annotated. To date, only a few molecular tools are available and a few Next Generation Sequencing (NGS) studies have been performed. Here we aimed at setting-up an RNA extraction method to obtain high quality and sufficient quantity of RNA for NGS from P. lividus embryos at the pluteus stage. We compared five different RNA extraction protocols from four different pools of plutei (500, 1000, 2500 and 5000 embryos): TRIzol®, and four widely-used Silica Membrane kits, GenElute™ Mammalian Total RNA Miniprep Kit, RNAqueous® Micro Kit, RNeasy® Micro Kit and Aurum™ Total RNA Mini Kit. The quantity of RNA isolated was evaluated using NanoDrop. The quality, considering the purity, was measured as A260/A280 and A260/230 ratios. The integrity was measured by RNA Integrity Number (RIN). Our results demonstrated that the most efficient procedures were GenElute, RNeasy and Aurum, producing a sufficient quantity of RNA for NGS. The Bioanalyzer profiles and RIN values revealed that the most efficient methods guaranteeing for RNA integrity were RNeasy and Aurum combined with an initial preservation in RNAlater. This research represents the first attempt to standardize a method for high-quality RNA extraction from sea urchin embryos at the pluteus stage, providing a new resource for this established model marine organism.

The Seagrass Effect Turned Upside Down Changes the Prospective of Sea Urchin Survival and Landscape Implications.

Habitat structure plays an important mediating role in predator-prey interactions. However the effects are strongly dependent on regional predator pools, which can drive predation risk in habitats with very similar structure in opposite directions. In the Mediterranean Sea predation on juvenile sea urchins is commonly known to be regulated by seagrass structure. In this study we test whether the possibility for juvenile Paracentrotus lividus to be predated changes in relation to the fragmentation of the seagrass Posidonia oceanica (four habitat classes: continuous, low-fragmentation, high-fragmentation and rocks), and to the spatial arrangement of such habitat classes at a landscape scale. Sea urchin predation risk was measured in a 20-day field experiment on tethered individuals placed in three square areas 35×35 m2 in size. Variability of both landscape and habitat structural attributes was assessed at the sampling grain 5×5 m2. Predation risk changed among landscapes, as it was lower where more 'rocks', and thus less seagrass, were present. The higher risk was found in the 'continuous' P. oceanica rather than in the low-fragmentation, high-fragmentation and rock habitats (p-values = 0.0149, 0.00008, and 0.0001, respectively). Therefore, the expectation that juvenile P. lividus survival would have been higher in the 'continuous' seagrass habitat, which would have served as shelter from high fish predation pressure, was not met. Predation risk changed across habitats due to different success between attack types: benthic attacks (mostly from whelks) were overall much more effective than those due to fish activity, the former type being associated with the 'continuous' seagrass habitat. Fish predation on juvenile sea urchins on rocks and 'high-fragmentation' habitat was less likely than benthic predation in the 'continuous' seagrass, with the low seagrass patch complexity increasing benthic activity. Future research should be aimed at investigating, derived from the complex indirect interactions among species, how top-down control in marine reserves can modify seagrass habitat effects.

Assessment of the individual and mixture toxicity of cadmium, copper and oxytetracycline, on the embryo-larval development of the sea urchin Paracentrotus lividus.

Multiple pollutions by trace metals and pharmaceuticals have become one of the most important problems in marine coastal areas because of its excessive toxicity on organisms living in this area. This study aimed to assess the individual and mixture toxicity of Cu, Cd, and oxytetracycline frequently existing in the contaminated marine areas and the embryo-larval development of the sea urchin Paracentrotus lividus. The individual contamination of the spermatozoid for 1 h with the increasing concentrations of Cd, Cu, and OTC decreases the fertility rate and increases larvae anomalies in the order Cu > Cd > OTC. Moreover, the normal larva frequency and the length of spicules were more sensitive than the fertilization rate and normal gastrula frequency endpoints. The mixture toxicity assessed by multiple experimental designs showed clearly that concentrations of Cd, Cu, and OTC superior to 338 µg/L, 0.56 µg/L, and 0.83 mg/L, respectively, cause significant larva malformations.

Subtle reproductive impairment through nitric oxide-mediated mechanisms in sea urchins from an area affected by harmful algal blooms.

The health of the sea urchin Paracentrotus lividus, a key species in the Mediterranean Sea, is menaced by several pressures in coastal environments. Here, we aimed at assessing the reproductive ability of apparently healthy P. lividus population in a marine protected area affected by toxic blooms of Ostreospsis cf. ovata. Wide-ranging analyses were performed in animals collected prior to and during the bloom, as well as at several times thereafter, during the reproductive season. Adults showed a low fertilization rate, along with high nitric oxide (NO) levels in the gonads and the nitration of the major yolk protein toposome, which is an important player in sea urchin development. Serious developmental anomalies were observed in the progeny, which persist several months after the bloom. NO levels were high in the different developmental stages, which also showed variations in the transcription of several genes that were found to be directly or indirectly modulated by NO. These results highlight subtle but important reproductive flaws transmitted from the female gonads to the offspring with the NO involvement. Despite a recovery along time after the bloom, insidious damages can be envisaged in the local sea urchin population, with possible reverberation on the whole benthic system.

Ocean warming ameliorates the negative effects of ocean acidification on Paracentrotus lividus larval development and settlement.

Ocean warming and acidification both impact marine ecosystems. All organisms have a limited body temperature range, outside of which they become functionally constrained. Beyond the absolute extremes of this range, they cannot survive. It is hypothesized that some stressors can present effects that interact with other environmental variables, such as ocean acidification (OA) that have the potential to narrow the thermal range where marine species are functional. An organism's response to ocean acidification can therefore be highly dependent on thermal conditions. This study evaluated the combined effects of predicted ocean warming conditions and acidification, on survival, development, and settlement, of the sea urchin Paracentrotus lividus. Nine combined treatments of temperature (19.0, 20.5 and 22.5 °C) and pH (8.1, 7.7 and 7.4 units) were carried out. All of the conditions tested were either within the current natural ranges of seawater pH and temperature or are within the ranges that have been predicted for the end of the century, in the sampling region (Canary Islands). Our results indicated that the negative effects of low pH on P. lividus larval development and settlement will be mitigated by a rise in seawater temperature, up to a thermotolerance threshold. Larval development and settlement performance of the sea urchin P. lividus was enhanced by a slight increase in temperature, even under lowered pH conditions. However, the species did show negative responses to the levels of ocean warming and acidification that have been predicted for the turn of the century.

Multidisciplinary screening of toxicity induced by silica nanoparticles during sea urchin development.

The aim of this study was to investigate the potential toxicity of Silica nanoparticles (SiO2 NPs) in seawater by using the sea urchin Paracentrotus lividus as biological model. SiO2 NPs exposure effects were identified on the sperm of the sea urchin through a multidisciplinary approach, combining developmental biology, ecotoxicology, biochemistry, and microscopy analyses. The following responses were measured: (i) percentage of eggs fertilized by exposed sperm; (ii) percentage of anomalies and undeveloped embryos and larvae; (iii) enzyme activity alterations (acetylcholinesterase, AChE) in the early developmental stages, namely gastrula and pluteus. Sperms were exposed to seawater containing SiO2 NPs suspensions ranging from 0.0001mg/L to 50mg/L. Fertilization ability was not affected at any concentration, whereas a significant percentage of anomalies in the offspring were observed and quantified by means of EC50 at gastrula stage, including undeveloped and anomalous embryos (EC50=0.06mg/L), and at pluteus stage, including skeletal anomalies and delayed larvae (EC50=0.27mg/L). Moreover, morphological anomalies were observed in larvae at pluteus stage, by immunolocalizing molecules involved in larval development and neurotoxicity effects - such as acetylated tubulin and choline acetyltransferase (ChAT) - and measuring AChE activity. Exposure of sea urchins to SiO2 NPs caused neurotoxic damage and a decrease of AChE expression in a non-dose-dependent manner. In conclusion, through the multidisciplinary approach used in this study SiO2 NPs toxicity in sea urchin offspring could be assessed. Therefore, the measured responses are suitable for detecting embryo- and larval- toxicity induced by these NPs.

Crecimiento y mejora del índice gonadal en el cultivo del erizo de mar Paracentrotus lividus (Echinoida: Echinidae) en Galicia (España) / Growth rate and gonadal index improvement in sea urchin culture Paracentrotus lividus (Echinoida: Echinidae)

Resumen La gran demanda de Paracentrotus lividus (Lamarck, 1816) en países como Francia, Italia, Turquía, Bélgica o Japón, ha elevado el nivel de extracción de este equinodermo en los últimos años que ha generado un desgaste en las poblaciones de erizos, los cuales tardan años en regenerarse. La importancia económica de P. lividus en Galicia, con una producción media anual de 700 000 kg y un valor cercano a los 2 millones de € en el año 2013, nos ha llevado a realizar diversas experiencias con el objetivo de analizar las posibilidades del cultivo en Galicia de esta especie en batea. Se han diseñado tres experiencias: 1) Efecto de cinco dietas y tres densidades sobre el crecimiento de juveniles de P. lividus obtenidos del medio natural; (2) Crecimiento de juveniles de P. lividus obtenidos en criadero, alimentados con algas, y 3) Efecto de diferentes dietas experimentales sobre el índice gonadal de P. lividus de tamaño comercial. Las experiencias se realizaron en una batea de la USC situada en la ría de Muros-Noia (Galicia), durante cuatro años (2007 - 2010), utilizando 2 231 erizos en total, procedentes del medio natural (450), de criadero (773) y de tamaño comercial (1 008), diseñándose diversas dietas experimentales que tratan de incrementar el crecimiento somático y gonadal de los erizos, con el fin de reducir el tiempo de crecimiento de los juveniles procedentes del medio natural y de criadero hasta que alcancen la talla comercial (55 mm de diámetro), o bien hasta que consigan un tamaño adecuado para repoblar las zonas sobreexplotadas del medio natural (20 mm de diámetro), así como el crecimiento de las gónadas de erizos comerciales con diferentes dietas. Mensualmente se tomó el diámetro de los erizos juveniles con el fin de determinar el efecto de las diferentes dietas y densidades sobre el crecimiento de los mismos, así como la determinación del índice gonadal (IG) en los erizos de tamaño comercial para ver el efecto de las diferentes dietas ensayadas. Con los datos obtenidos estimamos que, en la actualidad, no sería rentable alimentar erizos juveniles de P. lividus en batea hasta alcanzar la talla comercial, debido al bajo precio que tiene esta especie en el mercado (3€ / kg aproximadamente), aunque sí sería interesante mantenerlos en cultivo en batea hasta que alcancen el tamaño óptimo para repoblar zonas donde las poblaciones naturales están mermadas, combinando esto con el engorde de gónadas con alguno de los piensos diseñados que aumenta el IG y amplía el tiempo de explotación comercial de los erizos.

Abstract The high demand for Paracentrotus lividus (Lamarck, 1816) in countries like France, Italy, Turkey, Belgium and Japan, has raised the level of extraction of this echinoderm in recent years and has generated wear urchin populations, which take years to regenerate. The economic importance of P. lividus in Galicia, with an average annual production of 700≤000 kg and a value close to € 2 million in 2013, has led us to perform a variety of experiences in order to analyze the possibilities of the culture of this species in Galicia in raft. We have designed three experiences: 1) Effect of five diets and three densities on the growth of juvenile P. lividus obtained from the natural environment; 2) Growth of juvenile P. lividus obtained from hatchery, fed algae, and 3) Effect of different experimental diets on gonadal index of P. lividus commercial size. The experiments were performed on a USC raft situated in the estuary of Muros-Noia (Galicia) for four years (2007 - 2010), using 2 231 total urchins, from the natural environment (450), hatchery (773) and market size (1 008), being designed various experimental diets that try to increase somatic and gonadal growth in sea urchins, in order to reduce the rise time of juveniles from the wild and hatchery until they reach the size commercial (55 mm diameter), or until they get a suitable size to repopulate overfished areas of the natural environment (20 mm diameter), and the growth of the gonads of sea urchins with different diets. Monthly has taken diameter of juvenile sea urchins in order to determine the effect of different diets on growth and densities of the same, as well as determining the gonadal index (GI) in sea urchins of commercial size to see the effect took different tested diets. With the data obtained estimates that, at present, it would be profitable to feed juvenile sea urchins P. lividus in raft to reach commercial size, due to the low price of this species in the market (3€ / kg). Additonally they could reach optimum size and be used to repopulate areas where natural populations are depleted. This should be combined with the fattening of gonads and extended time of commercial exploitation. Rev. Biol. Trop. 63 (Suppl. 2): 261-272. Epub 2015 June 01.