Arbacia Lixula Research Articles

Echinodermata in ecotoxicological tests: maintenance and sensitivity

Abstract This work investigates the sensitivity of four species of Echinodermata (Lytechinus variegatus, Echinometra lucunter, Arbacia lixula and Encope emarginata), evaluating the effect of five reference toxicants (Cd, Pb, Cr, Cu and SDS) on embryo-larval development, following the official protocols. It also evaluates techniques for the maintenance of L. variegatus in the laboratory, changes in its sensitivity, and the effects of chemical agents that induce the release of gametes, on the survival rates of the organisms. In terms of the maintenance of L. variegatus in the laboratory, the diet with vegetable content appears to be more favorable for maintenance and maturation in cultivation tanks. Chemical inducers such as KCl and the Anesthetic (lidocaine and epinephrine) resulted in high adult mortality rates, discouraging its re-induction. The tests performed with different species of sea urchin and sand dollar, using different reference toxicants, showed no variations in sensitivity to the more toxic chemicals, indicating that different species can be used for evaluation and environmental impact assessment.

The elusive Arbaciella elegans is but the juvenile of the abundant echinoid Arbacia lixula

Event Abstract Back to Event The elusive Arbaciella elegans is but the juvenile of the abundant echinoid Arbacia lixula Maria Casso1*, Owen S. Wangensteen2, Cataixa Lopez3 and Creu Palacin4 1 Spanish National Research Council, Center for Advanced Studies of Blanes, Spain 2 University of Salford, School of Environment and Life Sciences, United Kingdom 3 Universidad de La Laguna, Facultad de Biología, Spain 4 Universitat de Barcelona, Facultat de Biologia, Spain Arbaciella elegans Mortensen, 1910 is a rarely reported and poorly known echinoid species, closely related to Arbacia lixula (Linnaeus, 1758). Some similarities between both species and the lack of a complete description for A. lixula juveniles have led to reasonable doubts regarding the validity of A. elegans. We used 70 individuals from most of the distribution area of A. elegans (which closely matches that of A. lixula) for morphological analyses and phylogenetic barcoding using the mitochondrial marker COI. Our morphological results indicate that the diagnostic characters for A. elegans are not strong enough to distinguish it from A. lixula, as the shape, colour and distribution of spines are highly variable, and the presence of gonopores is not an indicative of maturity. Moreover, the COI barcoding analysis proved that all the samples morphologically compatible as A. elegans clearly lie within the range of genetic variability of A. lixula, including many shared haplotypes. Finally, we obtained A. lixula larvae from in vitro fertilization of gametes and reared them to complete development in aquaria, proving that the morphology of recently settled juveniles of A. lixula closely matches the description of A. elegans. Therefore, we conclude that A. elegans is actually the juvenile form of A. lixula and that the genus Arbaciella must be regarded as invalid. Keywords: Arbaciella elegans, Arbacia lixula, Taxonomy, synonym, juvenile Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016. Presentation Type: Oral Presentation Topic: 1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS Citation: Casso M, Wangensteen OS, Lopez C and Palacin C (2016). The elusive Arbaciella elegans is but the juvenile of the abundant echinoid Arbacia lixula. Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00013 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Apr 2016; Published Online: 02 Sep 2016. * Correspondence: Ms. Maria Casso, Spanish National Research Council, Center for Advanced Studies of Blanes, Blanes, Spain, mariacasso85@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Maria Casso Owen S Wangensteen Cataixa Lopez Creu Palacin Google Maria Casso Owen S Wangensteen Cataixa Lopez Creu Palacin Google Scholar Maria Casso Owen S Wangensteen Cataixa Lopez Creu Palacin PubMed Maria Casso Owen S Wangensteen Cataixa Lopez Creu Palacin Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Analysis of Variability in Embryological Response of Two Sea Urchin Species to Spatial and Temporal features-Can these Factors Influence Responses in Standardized Ecotoxicological Assays?

Analysis of Variability in Embryological Response of Two Sea Urchin Species to Spatial and Temporal features-Can these Factors Influence Responses in Standardized Ecotoxicological Assays? The use of Echinoderms as bioindicator organisms, in particular in emryotoxicity test with Paracentrotus lividus and Arbacia lixula, has provided the scientific community with a remarkable number of ecotoxicological studies. In this experiment, the responses of these two species were analysed considering the spatial and temporal variability of three populations distributed in a radius of ca 10 km. The species tested in this experiment demonstrated an overall substantial different response towards metals (p<0.001), Arbacia lixula being the most sensitive species to both the three different sites and different periods of the year when adults were collected. There was a significant difference among populations for both species. The site affected most by the metal toxicity was Fortullino, which is the less human impacted area. In general, as a consequence of the passed reproductive season, embryos developed from gametes collected in May were the most affected in this study, confirming previous observations collected by our research group. No statistical difference has been recorded between the T1 (January) sampling corresponding to the beginning of reproductive season and the T5 (November) sampling-related embryos, which had the summer and the beginning of autumn as recovery period for their gamete production.

Characterization of the Teeth Skeletal Matrix from &lt;i&gt;Arbacia lixula&lt;/i&gt;

The teeth of sea urchins are highly complex composite structures, composed predominantly of high magnesium calcite, and of a minor heterogeneous assemblage of organic macromolecules that are occluded within the mineral. The organic matrix fulfils important functions in mineralization, in addition to giving the mineral phase peculiar mechanical properties, different from that of purely inorganic calcite. Nevertheless, the composition and function of individual components of the organic matrix still remains largely unknown. Up to now, the detailed protein repertoire of teeth from a single sea urchin species (Strongylocentrotus purpuratus, order Camarodonta) was investigated. In this study, we characterized for the first time the teeth skeletal matrix of another sea urchin, Arbacia lixula (order Arbacioida). The acetic acid soluble and acetic acid insoluble matrices, namely ASM and AIM respectively, were extracted and characterized with different biochemical methods including mono-dimensional SDS-PAGE, FT-IR spectroscopy, HPAE-PAD for monosaccharide analysis, and finally, proteomics. In spite of the paucity of peptide data, several of them displayed a high abundance of hydrophobic residues, i.e., alanine, glycine and valine, and of the apolar proline. We assert that the alanine- and proline-rich domains are important features of some of the matrix proteins associated to the teeth of sea urchins. None of the known skeletal matrix proteins from S. purpuratus teeth were identified in the organic matrix of A. lixula teeth. This might suggest major differences in teeth matrix protein repertoires of these two species belonging to orders that diverged in the Mesozoic times.

Sulphur-Containing Compounds as a Response in Sea Urchins Exposed to Alkylated Silicon Nanocrystals and SiO&lt;sub&gt;2&lt;/sub&gt;-Coated Iron Oxide Nanoparticles

We report the effects of exposure to alkylated silicon nanocrystals (‘alkyl-SiNCs’ at concentration ~ 7.2 mg/L) and -Fe2O3 nanoparticles coated with ultra-thin silica (‘SiO2-coated IONPs’ at concentration ~ 150 mg/L) on sea urchins Paracentrotus lividus and Arbacia lixula, respectively, studied with X-ray fluorescence (XRF) and Fourier transform infrared (FTIR) spectroscpoies using excitation from a synchrotron light source. A remarkably low mortality and low incidence of skeletal deformation is observed for exposure to both types of nanoparticles studied, despite the high concentrations employed in this work. XRF mapping demonstrates that both types of nanoparticle are found to agglomerate in the body of the sea urchins. FTIR spectra indicates that alkyl-SiNCs remain intact after ingestion and corresponding XRF maps show increased an oxygen throughout the organisms, possibly related to oxidation products arising from reactive oxygen species generated in the presence of the nanoparticles. Exposure to SiO2-coated IONPs is found to produce sulphur-containing species, which may be the result of a biological response in order to reduce the toxicity of the nanomaterial.

New Invertebrate Vectors of Okadaic Acid from the North Atlantic Waters—Portugal (Azores and Madeira) and Morocco

Okadaic acid and its analogues are potent phosphatase inhibitors that cause Diarrheic Shellfish Poisoning (DSP) through the ingestion of contaminated shellfish by humans. This group of toxins is transmitted worldwide but the number of poisoning incidents has declined over the last 20 years due to legislation and monitoring programs that were implemented for bivalves. In the summer of 2012 and 2013, we collected a total of 101 samples of 22 different species that were made up of benthic and subtidal organisms such echinoderms, crustaceans, bivalves and gastropods from Madeira, São Miguel Island (Azores archipelago) and the northwestern coast of Morocco. The samples were analyzed by UPLC-MS/MS. Our main objective was to detect new vectors for these biotoxins. We can report nine new vectors for these toxins in the North Atlantic: Astropecten aranciacus, Arbacia lixula, Echinaster sepositus, Holothuria sanctori, Ophidiaster ophidianus, Onchidella celtica, Aplysia depilans, Patella spp., and Stramonita haemostoma. Differences in toxin contents among the species were found. Even though low concentrations were detected, the levels of toxins that were present, especially in edible species, indicate the importance of these types of studies. Routine monitoring should be extended to comprise a wider number of vectors other than for bivalves of okadaic acid and its analogues.

Temporal fluctuations in seawater pCO2 may be as important as mean differences when determining physiological sensitivity in natural systems

AbstractMost studies assessing the impacts of ocean acidification (OA) on benthic marine invertebrates have used stable mean pH/pCO2 levels to highlight variation in the physiological sensitivities in a range of taxa. However, many marine environments experience natural fluctuations in carbonate chemistry, and to date little attempt has been made to understand the effect of naturally fluctuating seawater pCO2 (pCO2sw) on the physiological capacity of organisms to maintain acid–base homeostasis. Here, for the first time, we exposed two species of sea urchin with different acid–base tolerances, Paracentrotus lividus and Arbacia lixula, to naturally fluctuating pCO2sw conditions at shallow water CO2 seep systems (Vulcano, Italy) and assessed their acid–base responses. Both sea urchin species experienced fluctuations in extracellular coelomic fluid pH, pCO2, and [HCO3−] (pHe, pCO2e, and [HCO3−]e, respectively) in line with fluctuations in pCO2sw. The less tolerant species, P. lividus, had the greatest capacity for [HCO3−]e buffering in response to acute pCO2sw fluctuations, but it also experienced greater extracellular hypercapnia and acidification and was thus unable to fully compensate for acid–base disturbances. Conversely, the more tolerant A. lixula relied on non-bicarbonate protein buffering and greater respiratory control. In the light of these findings, we discuss the possible energetic consequences of increased reliance on bicarbonate buffering activity in P. lividus compared with A. lixula and how these differing physiological responses to acute fluctuations in pCO2sw may be as important as chronic responses to mean changes in pCO2sw when considering how CO2 emissions will affect survival and success of marine organisms within naturally assembled systems.

Abundance, size composition and benthic assemblages of two Mediterranean echinoids off the Egyptian coasts: Paracentrotus lividus and Arbacia lixula

This study is concerned with the variability in abundance, size composition and benthic assemblages of two echinoid species, the common sea urchin Paracentrotus lividus (Lamarck, 1816) and black urchin Arbacia lixula (Linnaeus, 1758) in the Southeastern Mediterranean (SEM) along the coast of Alexandria, Egypt. Four seasonal trips were made during the years 2014–2015 covering 55km of the shore with depths ranging between 3 and 9m. The sea urchin species composition, density and size structure and distribution were compared. The associated macrobenthic invertebrates with prominent presence and biomass were observed as well as other benthic fauna and flora associations. The present results showed that P. lividus was the dominant echinoid spatially and temporally. A. lixula showed frequent occurrence in Sidi Bishr and Sidi Gaber stations in the spring season. The most dominant size class was the medium to large-sized classes for P. lividus and large-sized classes for A. lixula. The commercial size for the edible P. lividus represented 33% of the sampled population. Furthermore, the most dominant macrobenthic assemblages beside the echinoid population were primarily oysters, sea cucumbers, and mussels. Beside these, assemblage of seaweeds (red, green, brown and crustose algae), Porifera, Cnidaria, Crustacea, other Echinodermata, Bivalvia, Gastropoda, Tunicata, Bryozoa and Annelida were found. The present study shows that the investigated area represents stable habitats for the echinoid population with rich and diversified algal assemblages as well as other potential food resources.

Developmental abnormalities and neurotoxicological effects of CuO NPs on the black sea urchin Arbacia lixula by embryotoxicity assay

The embryotoxicity of CuO NPs was evaluated in the black sea urchin Arbacia lixula embryos, by using 24-well plates. Fertilized eggs were exposed to five doses of CuO NPs ranging from 0.07 to 20 ppb, until pluteus stage. CuO NPs suspensions in artificial seawater formed agglomerates of 80–200 nm size, and copper uptake was 2.5-fold up in larvae exposed to high NP concentrations in respect to control. Developmental delay and morphological alteration, including skeletal abnormalities, were observed, as well as impairment in cholinergic and serotonergic nervous systems. These findings suggest the potential of CuO NPs to interfere with the normal neurotransmission pathways, thus affecting larval morphogenesis. Overall, the embryotoxicity tests are effective for evaluation of nanoparticle effects on the health of aquatic biota. Furthermore, as the black sea urchin A. lixula demonstrated to be vulnerable to NP exposure, it may be a valid bioindicator in marine biomonitoring and ecotoxicological programmes.

Spine and test skeletal matrices of the Mediterranean sea urchin Arbacia lixula--a comparative characterization of their sugar signature.

Calcified structures of sea urchins are biocomposite materials that comprise a minor fraction of organic macromolecules, such as proteins, glycoproteins and polysaccharides. These macromolecules are thought to collectively regulate mineral deposition during the process of calcification. When occluded, they modify the properties of the mineral. In the present study, the organic matrices (both soluble and insoluble in acetic acid) of spines and tests from the Mediterranean black sea urchin Arbacia lixula were extracted and characterized, in order to determine whether they exhibit similar biochemical signatures. Bulk characterizations were performed by mono-dimensional SDS/PAGE, FT-IR spectroscopy, and an in vitro crystallization assay. We concentrated our efforts on characterization of the sugar moieties. To this end, we determined the monosaccharide content of the soluble and insoluble organic matrices of A. lixula spines and tests by HPAE-PAD, together with their respective lectin-binding profiles via enzyme-linked lectin assay. Finally, we performed in situ localization of N-acetyl glucosamine-containing saccharides on spines and tests using gold-conjugated wheatgerm agglutinin. Our data show that the test and spine matrices exhibit different biochemical signatures with regard to their saccharidic fraction, suggesting that future studies should analyse the regulation of mineral deposition by the matrix in these two mineralized structures in detail. This study re-emphasizes the importance of non-protein moieties, i.e. sugars, in calcium carbonate systems, and highlights the need to clearly identify their function in the biomineralization process.

The test skeletal matrix of the black sea urchin Arbacia lixula

In the field of biomineralization, the past decade has been marked by the increasing use of high throughput techniques, i.e. proteomics, for identifying in one shot the protein content of complex macromolecular mixtures extracted from mineralized tissues. Although crowned with success, this approach has been restricted so far to a limited set of key-organisms, such as the purple sea urchin Strongylocentrotus purpuratus, the pearl oyster or the abalone, leaving in the shadow non-model organisms. As a consequence, it is still unknown to what extent the calcifying repertoire varies, from group to group, at high (phylum, class), median (order, family) or low (genus, species) taxonomic rank.The present paper shows the first biochemical and proteomic characterization of the test matrix of the Mediterranean black sea urchin Arbacia lixula (Arbacioida). Our work suggests that the skeletal repertoire of A. lixula exhibits some similarities but also several differences with that of the few sea urchin species (S. purpuratus, Paracentrotus lividus), for which molecular data are already available. The differences may be attributable to the taxonomic position of the species considered: A. lixula belongs to an order – Arbacioida – that diverged more than one hundred million years ago from the Camarodonta, which includes the two species S. purpuratus and P. lividus. For the echinoid class, we suggest that large-scale proteomic screening should be performed in order to understand which molecular functions related to calcification are conserved and which ones have been co-opted for biomineralization in particular lineages.

Role of two co-occurring Mediterranean sea urchins in the formation of barren from Cystoseira canopy

In the Mediterranean Sea the co-occurring sea urchins Paracentrotus lividus and Arbacia lixula are usually considered to share the same ecological role in the formation of barren from Cystoseira canopy. However, their foraging ability may vary due to feeding behavior and species-specific morphological traits. The relative effects of P. lividus and A. lixula on Cystoseira canopy was tested experimentally both in the laboratory, at a density of about 20 ind./m2, and in the field by gut content analysis. Field and laboratory results show that A. lixula is unable to affect Cystoseira spp. Furthermore, these results confirmed the great ability of P. lividus to consume Cystoseira canopy, thus supporting the evidence of the major role of this species in the creation of a barren state.

Patterns of distribution and composition of sea urchin assemblages on Brazilian subtropical rocky reefs

Sea urchins are a key group of herbivores in both temperate and tropical food webs because they control macroalgal cover, and consequently influence primary productivity and phase shifts on reefs. Despite being abundant on southwestern Atlantic reefs, sea urchin distributions, and their association with abiotic and biotic variables, are poorly known. In this study, sea urchin assemblages were surveyed in 2011 at multiple depths at eight sites in Arraial do Cabo (Brazil, 22°57′S/41°01′W), with sites split between a colder, more wave-exposed location, and a warmer, more sheltered location. The influence of this large-scale physical gradient, along with changes in depth and substrate complexity, on sea urchin densities was then investigated. Predator biomass was low and did not vary significantly among sites. Among the seven species recorded, Paracentrotus gaimardi, Echinometra lucunter and Arbacia lixula were dominant. Linear mixed-effects models indicated that location was important, with mid-sized P. gaimardi individuals and A. lixula more common at cooler, exposed sites and E. lucunter more abundant at warmer, sheltered sites. Sea urchin densities typically decreased with increasing depth, probably caused by changes in factors such as light, wave exposure, and sedimentation. Substrate complexity had a positive effect on the abundance of all species, presumably because of the increased availability of refuges. Physical gradients have important consequences for urchin distributions and their ecological functions at relatively small spatial scales on these reefs, and should be incorporated into herbivore monitoring programmes. Research is also required to examine how differential sea urchin distributions affect benthic dynamics.

Sea urchin response to rising pCO2 shows ocean acidification may fundamentally alter the chemistry of marine skeletons

Ocean acidification caused by an increase in pCO2 is expected to drastically affect marine ecosystem composition, yet there is much uncertainty about the mechanisms through which ecosystems may be affected. Here we studied sea urchins that are common and important grazers in the Mediterranean (Paracentrotus lividus and Arbacia lixula). Our study included a natural CO2 seep plus reference sites in the Aegean Sea off Greece. The distribution of A. lixula was unaffected by the low pH environment, whereas densities of P. lividus were much reduced. There was skeletal degradation in both species living in acidified waters compared to reference sites and remarkable increases in skeletal manganese levels (P. lividus had a 541% increase, A. lixula a 243% increase), presumably due to changes in mineral crystalline structure. Levels of strontium and zinc were also altered. It is not yet known whether such dramatic changes in skeletal chemistry will affect coastal systems but our study reveals a mechanism that may alter inter-species interactions.

Contrasting recruitment seasonality of sea urchin species in Gran Canaria, Canary Islands (eastern Atlantic)

Despite sea-urchins can play an important role affecting the community structure of subtidal bottoms, factors controlling the dynamics of sea-urchin populations are still poorly understood. We assessed the seasonal variation in recruitment of three sea-urchin species (Diadema africanum, Paracentrotus lividus and Arbacia lixula) at Gran Canaria Island (eastern Atlantic) via monthly deployment of artificial collectors throughout an entire annual cycle on each of four adjacent habitat patches (seagrasses, sandy patches, ‘urchin-grazed’ barrens and macroalgal-dominated beds) within a shallow coastal landscape. Paracentrotus lividus and A. lixula had exclusively one main recruitment peak in late winter-spring. Diadema africanum recruitment was also seasonal, but recruits appeared in late summer-autumn, particularly on ‘urchin-grazed’ barrens with large abundances of adult conspecifics. In conclusion, this study has demonstrated non-overlapping seasonal recruitment patterns of the less abundant species (P. lividus and A. lixula) with the most conspicuous species (D. africanum) in the study area.

Identification of the toxic constituents of sediments in a Brazilian subtropical estuary

Phase 1 of the TIE method was applied to samples of elutriates from sediments of the Itajaí-Açu estuary and adjacent coastal region in southern Brazil. Embryo-larval toxicity assays were used with the sea urchin Arbacia lixula in samples of raw elutriate, and treated with Ulva fasciata, EDTA and sodium thiosulfate. Inside the estuary, ammonia was responsible for more than 40% of the toxicity in both the dredged and undredged regions. A toxicity gradient was observed, between the estuary and the coastal region, with an increase in the importance of metals for the latter. Temporally, there is strong evidence of the influence of dredging and disposal of sediments in the contamination of the coastal dumping site. The results indicating that this area presents limitations in its saturation capacity. Chemical analysis indicated the metal Cu is probably responsible for the toxicity of the sediments observed, without the interference of ammonia.

Some like it hot: Temperature and pH modulate larval development and settlement of the sea urchin Arbacia lixula

We studied the effects of temperature and pH on larval development, settlement and juvenile survival of a Mediterranean population of the sea urchin Arbacia lixula. Three temperatures (16, 17.5 and 19°C) were tested at present pH conditions (pHT8.1). At 19°C, two pH levels were compared to reflect present average (pHT8.1) and near-future average conditions (pHT7.7, expected by 2100). Larvae were reared for 52-days to achieve the full larval development and complete the metamorphosis to the settler stage. We analyzed larval survival, growth, morphology and settlement success. We also tested the carry-over effect of acidification on juvenile survival after 3days. Our results showed that larval survival and size significantly increased with temperature. Acidification resulted in higher survival rates and developmental delay. Larval morphology was significantly altered by low temperatures, which led to narrower larvae with relatively shorter skeletal rods, but larval morphology was only marginally affected by acidification. No carry-over effects between larvae and juveniles were detected in early settler survival, though settlers from larvae reared at pH7.7 were significantly smaller than their counterparts developed at pH8.1. These results suggest an overall positive effect of environmental parameters related to global change on the reproduction of A. lixula, and reinforce the concerns about the increasing negative impact on shallow Mediterranean ecosystems of this post-glacial colonizer.

The reproductive cycle of the sea urchin Arbacia lixula in northwest Mediterranean: potential influence of temperature and photoperiod

We studied the reproductive cycle of the sea urchin Arbacia lixula in a subtidal population from northeast Spain over four years using a gonadosomatic index (GSI) and gonad histology. Our results show that the GSI of A. lixula follows a seasonal cycle which peaks in May–July and attains its lowest values in October–November every year. The time course of the GSI matched closely the photoperiod cycle. We also found a remarkable inter-annual variability in the maximum value of GSI, which correlated with mean water temperature during the gonad growth period (winter and spring). Gonad histology was also in agreement with a single gametogenic cycle per year in this species. We explored the application of circular statistics to present and analyse gonadal development data, which allowed us to adequately handle the high intra-individual variability detected, with several developmental stages commonly found within the same gonad. The picture that emerged is one of a gametogenic timing driven by photoperiod, while the amount of reproductive output is determined by temperature. This is coherent with the tropical origin of the species and lends support to recent warnings about an increase in the abundance of this species in the Mediterranean as a result of global warming, with associated increased impact potential in sublittoral communities.

Temperature modulates the response of the thermophilous sea urchin Arbacia lixula early life stages to CO2-driven acidification

The increasing abundances of the thermophilous black sea urchin Arbacia lixula in the Mediterranean Sea are attributed to the Western Mediterranean warming. However, few data are available on the potential impact of this warming on A. lixula in combination with other global stressors such as ocean acidification. The aim of this study is to investigate the interactive effects of increased temperature and of decreased pH on fertilization and early development of A. lixula. This was tested using a fully crossed design with four temperatures (20, 24, 26 and 27 °C) and two pH levels (pHNBS 8.2 and 7.9). Temperature and pH had no significant effect on fertilization and larval survival (2d) for temperature <27 °C. At 27 °C, the fertilization success was very low (<1%) and all larvae died within 2d. Both temperature and pH had effects on the developmental dynamics. Temperature appeared to modulate the impact of decreasing pH on the % of larvae reaching the pluteus stage leading to a positive effect (faster growth compared to pH 8.2) of low pH at 20 °C, a neutral effect at 24 °C and a negative effect (slower growth) at 26 °C. These results highlight the importance of considering a range of temperatures covering today and the future environmental variability in any experiment aiming at studying the impact of ocean acidification.

Evaluation of mysids and sea urchins exposed to saxitoxins

Saxitoxins are neurotoxins produced by dinoflagellates and cyanobacteria that form toxic blooms in waters. The impact of saxitoxins to the most vulnerable taxa and environment are not well understood. The experimental model was based on the use of toxic cell extracts containing saxitoxins. This extract was utilized for acute and chronic tests with Mysidopsis juniae. Chronic tests were also done with Lytechinus variegatus and Arbacia lixula larvae. Acute test with mysids had a LC50=2.34μg/L. The chronic test with sea urchins showed morphological abnormalities resulting in malformation of larval appendices at low concentrations of the toxin (EC50=2.96μg/L for L. variegatus and 2.06μg/L for A. lixula). Although saxitoxins are considered neurotoxins, both species of sea urchins showed symptoms not related to nerve cells. A. lixula was more sensitive than L. variegatus, proving that its sensitivity should be taken in consideration to be another option to toxicological tests.